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Zhang Y, Gu S, Du J, Huang G, Shi J, Lu X, Wang J, Yang W, Guo X, Zhao C. Plant microphenotype: from innovative imaging to computational analysis. PLANT BIOTECHNOLOGY JOURNAL 2024; 22:802-818. [PMID: 38217351 PMCID: PMC10955502 DOI: 10.1111/pbi.14244] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2023] [Revised: 11/09/2023] [Accepted: 11/11/2023] [Indexed: 01/15/2024]
Abstract
The microphenotype plays a key role in bridging the gap between the genotype and the complex macro phenotype. In this article, we review the advances in data acquisition and the intelligent analysis of plant microphenotyping and present applications of microphenotyping in plant science over the past two decades. We then point out several challenges in this field and suggest that cross-scale image acquisition strategies, powerful artificial intelligence algorithms, advanced genetic analysis, and computational phenotyping need to be established and performed to better understand interactions among genotype, environment, and management. Microphenotyping has entered the era of Microphenotyping 3.0 and will largely advance functional genomics and plant science.
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Affiliation(s)
- Ying Zhang
- Beijing Key Lab of Digital Plant, Information Technology Research Center, Beijing Academy of Agriculture and Forestry Sciences, Beijing, China
| | - Shenghao Gu
- Beijing Key Lab of Digital Plant, Information Technology Research Center, Beijing Academy of Agriculture and Forestry Sciences, Beijing, China
| | - Jianjun Du
- Beijing Key Lab of Digital Plant, Information Technology Research Center, Beijing Academy of Agriculture and Forestry Sciences, Beijing, China
| | - Guanmin Huang
- Beijing Key Lab of Digital Plant, Information Technology Research Center, Beijing Academy of Agriculture and Forestry Sciences, Beijing, China
| | - Jiawei Shi
- National Key Laboratory of Crop Genetic Improvement, National Center of Plant Gene Research, Hubei Hongshan Laboratory, Huazhong Agricultural University, Wuhan, China
| | - Xianju Lu
- Beijing Key Lab of Digital Plant, Information Technology Research Center, Beijing Academy of Agriculture and Forestry Sciences, Beijing, China
| | - Jinglu Wang
- Beijing Key Lab of Digital Plant, Information Technology Research Center, Beijing Academy of Agriculture and Forestry Sciences, Beijing, China
| | - Wanneng Yang
- National Key Laboratory of Crop Genetic Improvement, National Center of Plant Gene Research, Hubei Hongshan Laboratory, Huazhong Agricultural University, Wuhan, China
| | - Xinyu Guo
- Beijing Key Lab of Digital Plant, Information Technology Research Center, Beijing Academy of Agriculture and Forestry Sciences, Beijing, China
| | - Chunjiang Zhao
- Beijing Key Lab of Digital Plant, Information Technology Research Center, Beijing Academy of Agriculture and Forestry Sciences, Beijing, China
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Finch NC, Neal CR, Welsh GI, Foster RR, Satchell SC. The unique structural and functional characteristics of glomerular endothelial cell fenestrations and their potential as a therapeutic target in kidney disease. Am J Physiol Renal Physiol 2023; 325:F465-F478. [PMID: 37471420 PMCID: PMC10639027 DOI: 10.1152/ajprenal.00036.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2023] [Revised: 07/17/2023] [Accepted: 07/17/2023] [Indexed: 07/22/2023] Open
Abstract
Glomerular endothelial cell (GEnC) fenestrations are a critical component of the glomerular filtration barrier. Their unique nondiaphragmed structure is key to their function in glomerular hydraulic permeability, and their aberration in disease can contribute to loss of glomerular filtration function. This review provides a comprehensive update of current understanding of the regulation and biogenesis of fenestrae. We consider diseases in which GEnC fenestration loss is recognized or may play a role and discuss methods with potential to facilitate the study of these critical structures. Literature is drawn from GEnCs as well as other fenestrated cell types such as liver sinusoidal endothelial cells that most closely parallel GEnCs.
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Affiliation(s)
- Natalie C Finch
- Bristol Renal, University of Bristol, United Kingdom
- Langford Vets, University of Bristol, United Kingdom
| | - Chris R Neal
- Bristol Renal, University of Bristol, United Kingdom
| | - Gavin I Welsh
- Bristol Renal, University of Bristol, United Kingdom
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Kalmbach L, Bourdon M, Belevich I, Safran J, Lemaire A, Heo JO, Otero S, Blob B, Pelloux J, Jokitalo E, Helariutta Y. Putative pectate lyase PLL12 and callose deposition through polar CALS7 are necessary for long-distance phloem transport in Arabidopsis. Curr Biol 2023; 33:926-939.e9. [PMID: 36805125 DOI: 10.1016/j.cub.2023.01.038] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2022] [Revised: 11/12/2022] [Accepted: 01/19/2023] [Indexed: 02/18/2023]
Abstract
In plants, the phloem distributes photosynthetic products for metabolism and storage over long distances. It relies on specialized cells, the sieve elements, which are enucleated and interconnected through large so-called sieve pores in their adjoining cell walls. Reverse genetics identified PECTATE LYASE-LIKE 12 (PLL12) as critical for plant growth and development. Using genetic complementations, we established that PLL12 is required exclusively late during sieve element differentiation. Structural homology modeling, enzyme inactivation, and overexpression suggest a vital role for PLL12 in sieve-element-specific pectin remodeling. While short distance symplastic diffusion is unaffected, the pll12 mutant is unable to accommodate sustained plant development due to an incapacity to accommodate increasing hydraulic demands on phloem long-distance transport as the plant grows-a defect that is aggravated when combined with another sieve-element-specific mutant callose synthase 7 (cals7). Establishing CALS7 as a specific sieve pore marker, we investigated the subcellular dynamics of callose deposition in the developing sieve plate. Using fluorescent CALS7 then allowed identifying structural defects in pll12 sieve pores that are moderate at the cellular level but become physiologically relevant due to the serial arrangement of sieve elements in the sieve tube. Overall, pectin degradation through PLL12 appears subtle in quantitative terms. We therefore speculate that PLL12 may act as a regulator to locally remove homogalacturonan, thus potentially enabling further extracellular enzymes to access and modify the cell wall during sieve pore maturation.
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Affiliation(s)
- Lothar Kalmbach
- Sainsbury Laboratory, University of Cambridge, 47 Bateman Street, Cambridge CB2 1LR, UK.
| | - Matthieu Bourdon
- Sainsbury Laboratory, University of Cambridge, 47 Bateman Street, Cambridge CB2 1LR, UK
| | - Ilya Belevich
- Institute of Biotechnology, University of Helsinki, 00014 Helsinki, Finland
| | - Josip Safran
- UMR INRAE 1158 BioEcoAgro, BIOPI Biologie des Plantes et Innovation, Université de Picardie, 33 Rue St Leu, 80039 Amiens, France
| | - Adrien Lemaire
- UMR INRAE 1158 BioEcoAgro, BIOPI Biologie des Plantes et Innovation, Université de Picardie, 33 Rue St Leu, 80039 Amiens, France
| | - Jung-Ok Heo
- Sainsbury Laboratory, University of Cambridge, 47 Bateman Street, Cambridge CB2 1LR, UK; Institute of Biotechnology, University of Helsinki, 00014 Helsinki, Finland
| | - Sofia Otero
- Sainsbury Laboratory, University of Cambridge, 47 Bateman Street, Cambridge CB2 1LR, UK
| | - Bernhard Blob
- Sainsbury Laboratory, University of Cambridge, 47 Bateman Street, Cambridge CB2 1LR, UK
| | - Jérôme Pelloux
- UMR INRAE 1158 BioEcoAgro, BIOPI Biologie des Plantes et Innovation, Université de Picardie, 33 Rue St Leu, 80039 Amiens, France
| | - Eija Jokitalo
- Institute of Biotechnology, University of Helsinki, 00014 Helsinki, Finland
| | - Ykä Helariutta
- Sainsbury Laboratory, University of Cambridge, 47 Bateman Street, Cambridge CB2 1LR, UK; Institute of Biotechnology, University of Helsinki, 00014 Helsinki, Finland.
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Tixier A, Forest M, Prudent M, Durey V, Zwieniecki M, Barnard RL. Root exudation of carbon and nitrogen compounds varies over the day-night cycle in pea: The role of diurnal changes in internal pools. PLANT, CELL & ENVIRONMENT 2023; 46:962-974. [PMID: 36562125 DOI: 10.1111/pce.14523] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2022] [Revised: 12/13/2022] [Accepted: 12/20/2022] [Indexed: 06/17/2023]
Abstract
Rhizodeposition is the export of organic compounds from plant roots to the soil. Carbon allocation towards rhizodeposition has to be balanced with allocation for other physiological functions, which depend on both newly assimilated and stored nonstructural carbohydrate (NSC). To test whether the exudation of primary metabolites scales with plant NSC status, we studied diurnal dynamics of NSC and amino acid (AA) pools and fluxes within the plant and the rhizosphere. These diurnal dynamics were measured in the field and under hydroponic-controlled conditions. Further, C-limiting treatments offered further insight into the regulation of rhizodeposition. The exudation of primary metabolites fluctuated diurnally. The diurnal dynamics of soluble sugars (SS) and AA concentrations in tissues coincided with exudate pool fluctuations in the rhizosphere. SS and AA pools in the rhizosphere increased with NSC and AA pools in the roots. C starvation treatments offset the balance of exudates: AA exudate content in the rhizosphere significantly decreased while SS exudate content remained stable. Our results suggest that rhizodeposition is to some extent controlled by plant C:N status. We propose that SS exudation is less controlled than AA exudation because N assimilation depends on controlled C supply while SS exudation relies to a greater extent on passive diffusion mechanisms.
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Affiliation(s)
- Aude Tixier
- Agroécologie, AgroSup Dijon, INRAE, Université de Bourgogne, Université Bourgogne Franche-Comté, Dijon, France
| | - Marion Forest
- Agroécologie, AgroSup Dijon, INRAE, Université de Bourgogne, Université Bourgogne Franche-Comté, Dijon, France
| | - Marion Prudent
- Agroécologie, AgroSup Dijon, INRAE, Université de Bourgogne, Université Bourgogne Franche-Comté, Dijon, France
| | - Vincent Durey
- Agroécologie, AgroSup Dijon, INRAE, Université de Bourgogne, Université Bourgogne Franche-Comté, Dijon, France
| | - Maciej Zwieniecki
- Department of Plant Sciences, University of California, Davis, California, USA
| | - Romain L Barnard
- Agroécologie, AgroSup Dijon, INRAE, Université de Bourgogne, Université Bourgogne Franche-Comté, Dijon, France
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Losada JM, He Z, Holbrook NM. Sieve tube structural variation in Austrobaileya scandens and its significance for lianescence. PLANT, CELL & ENVIRONMENT 2022; 45:2460-2475. [PMID: 35606891 PMCID: PMC9540405 DOI: 10.1111/pce.14361] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/25/2021] [Revised: 04/15/2022] [Accepted: 04/23/2022] [Indexed: 06/15/2023]
Abstract
Lianas combine large leaf areas with slender stems, features that require an efficient vascular system. The only extant member of the Austrobaileyaceae is an endemic twining liana of the tropical Australian forests with well-known xylem hydraulics, but the vascular phloem continuum aboveground remains understudied. Microscopy analysis across leaf vein orders and stems of Austrobaileya scandens revealed a low foliar xylem:phloem ratio, with isodiametric vascular elements along the midrib, but tapered across vein orders. Sieve plate pore radii increased from 0.08 µm in minor veins to 0.12 µm in the petiole, but only to 0.20 µm at the stem base, tens of metres away. In easily bent searcher branches, phloem conduits have pectin-rich walls and simple plates, whereas in twining stems, conduits were connected through highly angled and densely porated sieve plates. The hydraulic resistance of phloem conduits in the twisted and elongated stems of A. scandens is large compared with trees of similar stature; phloem hydraulic resistance decreases from leaves to stems, consistent with the efficient delivery of photoassimilates from sources under Münch predictions. Sink strength of a continuously growing canopy might be stronger than in self-supporting understory plants, favoring resource allocation to aerial organs and the attainment of vertical stature.
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Affiliation(s)
- Juan M. Losada
- Institute for Mediterranean and Subtropical Horticulture ‘La Mayora’—CSIC—UMAAvda. Dr. Wienberg s/nAlgarrobo‐CostaMálaga29750Spain
- Department of Organismic and Evolutionary BiologyHarvard UniversityCambridgeMassachusettsUSA
- Arnold Arboretum of Harvard UniversityBostonMassachusettsUSA
| | - Zhe He
- Department of Organismic and Evolutionary BiologyHarvard UniversityCambridgeMassachusettsUSA
- Arnold Arboretum of Harvard UniversityBostonMassachusettsUSA
| | - N. Michele Holbrook
- Department of Organismic and Evolutionary BiologyHarvard UniversityCambridgeMassachusettsUSA
- Arnold Arboretum of Harvard UniversityBostonMassachusettsUSA
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D'Ascenzo N, Xie Q, Antonecchia E, Ciardiello M, Pagnani G, Pisante M. Kinetically Consistent Data Assimilation for Plant PET Sparse Time Activity Curve Signals. FRONTIERS IN PLANT SCIENCE 2022; 13:882382. [PMID: 35941942 PMCID: PMC9356293 DOI: 10.3389/fpls.2022.882382] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Accepted: 06/10/2022] [Indexed: 06/15/2023]
Abstract
Time activity curve (TAC) signal processing in plant positron emission tomography (PET) is a frontier nuclear science technique to bring out the quantitative fluid dynamic (FD) flow parameters of the plant vascular system and generate knowledge on crops and their sustainable management, facing the accelerating global climate change. The sparse space-time sampling of the TAC signal impairs the extraction of the FD variables, which can be determined only as averaged values with existing techniques. A data-driven approach based on a reliable FD model has never been formulated. A novel sparse data assimilation digital signal processing method is proposed, with the unique capability of a direct computation of the dynamic evolution of noise correlations between estimated and measured variables, by taking into explicit account the numerical diffusion due to the sparse sampling. The sequential time-stepping procedure estimates the spatial profile of the velocity, the diffusion coefficient and the compartmental exchange rates along the plant stem from the TAC signals. To illustrate the performance of the method, we report an example of the measurement of transport mechanisms in zucchini sprouts.
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Affiliation(s)
- Nicola D'Ascenzo
- School of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
- Department of Medical Physics and Engineering, Istituto Neurologico Mediterraneo, Istituto di Ricovero e Cura a Carattere Scientifico, Pozzilli, Italy
| | - Qingguo Xie
- School of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
- Department of Medical Physics and Engineering, Istituto Neurologico Mediterraneo, Istituto di Ricovero e Cura a Carattere Scientifico, Pozzilli, Italy
- Department of Electronic Engineering and Information Science, University of Science and Technology of China, Hefei, China
| | - Emanuele Antonecchia
- School of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
- Department of Medical Physics and Engineering, Istituto Neurologico Mediterraneo, Istituto di Ricovero e Cura a Carattere Scientifico, Pozzilli, Italy
| | - Mariachiara Ciardiello
- Department of Medical Physics and Engineering, Istituto Neurologico Mediterraneo, Istituto di Ricovero e Cura a Carattere Scientifico, Pozzilli, Italy
| | - Giancarlo Pagnani
- Faculty of Bioscience and Technology for Food, Agriculture and Environment, University of Teramo, Teramo, Italy
| | - Michele Pisante
- Faculty of Bioscience and Technology for Food, Agriculture and Environment, University of Teramo, Teramo, Italy
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Ostermeyer GP, Jensen KH, Franzen AR, Peters WS, Knoblauch M. Diversity of funnel plasmodesmata in angiosperms: the impact of geometry on plasmodesmal resistance. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2022; 110:707-719. [PMID: 35124855 DOI: 10.1111/tpj.15697] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2021] [Revised: 12/30/2021] [Accepted: 01/25/2022] [Indexed: 06/14/2023]
Abstract
In most plant tissues, threads of cytoplasm, or plasmodesmata, connect the protoplasts via pores in the cell walls. This enables symplasmic transport, for instance in phloem loading, transport and unloading. Importantly, the geometry of the wall pore limits the size of the particles that may be transported, and also (co-)defines plasmodesmal resistance to diffusion and convective flow. However, quantitative information on transport through plasmodesmata in non-cylindrical cell wall pores is scarce. We have found conical, funnel-shaped cell wall pores in the phloem-unloading zone in growing root tips of five eudicot and two monocot species, specifically between protophloem sieve elements and phloem pole pericycle cells. 3D reconstructions by electron tomography suggested that funnel plasmodesmata possess a desmotubule but lack tethers to fix it in a central position. Model calculations showed that both diffusive and hydraulic resistance decrease drastically in conical and trumpet-shaped cell wall pores compared with cylindrical channels, even at very small opening angles. Notably, the effect on hydraulic resistance was relatively larger. We conclude that funnel plasmodesmata generally are present in specific cell-cell interfaces in angiosperm roots, where they appear to facilitate symplasmic phloem unloading. Interestingly, cytosolic sleeves of most plasmodesmata reported in the literature do not resemble annuli of constant diameter but possess variously shaped widenings. Our evaluations suggest that widenings too small for unambiguous identification on electron micrographs may drastically reduce the hydraulic and diffusional resistance of these pores. Consequently, theoretical models assuming cylindrical symmetries will underestimate plasmodesmal conductivities.
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Affiliation(s)
- Grayson P Ostermeyer
- School of Biological Sciences, Washington State University, Pullman, WA, 99164, USA
| | - Kaare H Jensen
- Department of Physics, Technical University of Denmark, DK-2800 Kgs, Lyngby, Denmark
| | - Aslak R Franzen
- Department of Physics, Technical University of Denmark, DK-2800 Kgs, Lyngby, Denmark
| | - Winfried S Peters
- School of Biological Sciences, Washington State University, Pullman, WA, 99164, USA
- Department of Biology, Purdue University Fort Wayne, Fort Wayne, IN, 46805, USA
| | - Michael Knoblauch
- School of Biological Sciences, Washington State University, Pullman, WA, 99164, USA
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Peters WS, Knoblauch M. How Münch's adaptation of Pfeffer's circulating water flow became the pressure-flow theory, and the resulting problems - A historical perspective. JOURNAL OF PLANT PHYSIOLOGY 2022; 272:153672. [PMID: 35366573 DOI: 10.1016/j.jplph.2022.153672] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Revised: 03/16/2022] [Accepted: 03/17/2022] [Indexed: 06/14/2023]
Abstract
Long-distance transport of photoassimilates in the phloem of vascular plants occurs as bulk flow in sieve tubes. These tubes are arrays of cells that lose nuclei, cytoskeleton, and some organelles when they differentiate into mature sieve elements. Symplasmic continuity is achieved by perforations that turn the cell walls between adjoining sieve elements into sieve plates. These structural features are interpreted as adaptations that reduce the resistance sieve tubes offer to cytoplasmic bulk flow. According to the common reading of Ernst Münch's pressure-flow theory, the driving forces for these flows are osmotically generated gradients of hydrostatic pressure along the sieve tubes. However, the significance of pressure gradients in the flow direction has also been questioned. Münch himself stated that no detectable pressure gradients existed between the linked osmotic cells that he used to demonstrate the validity of his ideas, and the earliest explanation of osmotically driven flows by Wilhelm Pfeffer, on which Münch based his theory, explicitly claimed the absence of pressure gradients. To resolve the apparent contradiction, we here reconstruct the history of the idea that osmotically driven transport processes in organisms necessarily require steps or gradients of hydrostatic pressure along the transport route. Our analysis leads us to conclude that some defects of overly simplifying interpretations of Münch's ideas (such as the sieve plate fallacy) could be avoided if our descriptions of his theory in textbooks and the scientific literature would follow the logics of the theory's earliest formulations more closely.
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Affiliation(s)
- Winfried S Peters
- School of Biological Sciences, Washington State University, Pullman, WA, 99164, USA; Department of Biology, Purdue University Fort Wayne, Fort Wayne, IN, 46805, USA.
| | - Michael Knoblauch
- School of Biological Sciences, Washington State University, Pullman, WA, 99164, USA.
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Stanfield RC, Bartlett MK. Coordination Between Phloem Loading and Structure Maintains Carbon Transport Under Drought. FRONTIERS IN PLANT SCIENCE 2022; 13:787837. [PMID: 35251074 PMCID: PMC8891486 DOI: 10.3389/fpls.2022.787837] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Accepted: 01/27/2022] [Indexed: 06/14/2023]
Abstract
Maintaining phloem transport under water stress is expected to be crucial to whole-plant drought tolerance, but the traits that benefit phloem function under drought are poorly understood. Nearly half of surveyed angiosperm species, including important crops, use sucrose transporter proteins to actively load sugar into the phloem. Plants can alter transporter abundance in response to stress, providing a potential mechanism for active-loading species to closely regulate phloem loading rates to avoid drought-induced reductions or failures in phloem transport. We developed an integrated xylem-phloem-stomatal model to test this hypothesis by quantifying the joint impacts of transporter kinetics, phloem anatomy, and plant water status on sucrose export to sinks. We parameterized the model with phloem hydraulic resistances and sucrose transporter kinetic parameters compiled from the literature, and simulated loading regulation by allowing loading rates to decline exponentially with phloem pressure to prevent excessive sucrose concentrations from inducing viscosity limitations. In the absence of loading regulation, where loading rates were independent of phloem pressure, most resistance values produced unrealistic phloem pressures owing to viscosity effects, even under well-watered conditions. Conversely, pressure-regulated loading helped to control viscosity buildup and improved export to sinks for both lower and higher resistant phloem pathways, while maintaining realistic phloem pressures. Regulation also allowed for rapid loading and export in wet conditions while maintaining export and viable phloem pressures during drought. Therefore, we expect feedbacks between phloem pressure and loading to be critical to carbon transport in active-loading species, especially under drought, and for transporter kinetics to be strongly coordinated with phloem architecture and plant water status. This work provides an important and underexplored physiological framework to understand the ecophysiology of phloem transport under drought and to enhance the genetic engineering of crop plants.
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Affiliation(s)
- Ryan C. Stanfield
- Department of Viticulture and Enology, University of California, Davis, Davis, CA, United States
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10
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Barceló-Anguiano M, Holbrook NM, Hormaza JI, Losada JM. Changes in ploidy affect vascular allometry and hydraulic function in Mangifera indica trees. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2021; 108:541-554. [PMID: 34403543 DOI: 10.1111/tpj.15460] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Revised: 08/09/2021] [Accepted: 08/11/2021] [Indexed: 06/13/2023]
Abstract
The enucleated vascular elements of the xylem and the phloem offer an excellent system to test the effect of ploidy on plant function because variation in vascular geometry has a direct influence on transport efficiency. However, evaluations of conduit sizes in polyploid plants have remained elusive, most remarkably in woody species. We used a combination of molecular, physiological and microscopy techniques to model the hydraulic resistance between source and sinks in tetraploid and diploid mango trees. Tetraploids exhibited larger chloroplasts, mesophyll cells and stomatal guard cells, resulting in higher leaf elastic modulus and lower dehydration rates, despite the high water potentials of both ploidies in the field. Both the xylem and the phloem displayed a scaling of conduits with ploidy, revealing attenuated hydraulic resistance in tetraploids. Conspicuous wall hygroscopic moieties in the cells involved in transpiration and transport indicate a role in volumetric adjustments as a result of turgor change in both ploidies. In autotetraploids, the enlargement of organelles, cells and tissues, which are critical for water and photoassimilate transport at long distances, point to major physiological novelties associated with whole-genome duplication.
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Affiliation(s)
- Miguel Barceló-Anguiano
- Institute for Mediterranean and Subtropical Horticulture 'La Mayora' - CSIC - UMA, Avda. Dr. Wienberg s/n, Málaga, 29750, Spain
| | - N Michele Holbrook
- Department of Organismic and Evolutionary Biology, Harvard University, 16 Divinity Avenue, Cambridge, Massachusetts, 02138, USA
| | - José I Hormaza
- Institute for Mediterranean and Subtropical Horticulture 'La Mayora' - CSIC - UMA, Avda. Dr. Wienberg s/n, Málaga, 29750, Spain
| | - Juan M Losada
- Institute for Mediterranean and Subtropical Horticulture 'La Mayora' - CSIC - UMA, Avda. Dr. Wienberg s/n, Málaga, 29750, Spain
- Department of Organismic and Evolutionary Biology, Harvard University, 16 Divinity Avenue, Cambridge, Massachusetts, 02138, USA
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11
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Ray DM, Savage JA. Seasonal changes in temperate woody plant phloem anatomy and physiology: implications for long-distance transport. AOB PLANTS 2021; 13:plab028. [PMID: 34234934 PMCID: PMC8255074 DOI: 10.1093/aobpla/plab028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Accepted: 05/21/2021] [Indexed: 06/13/2023]
Abstract
Seasonal changes in climate are accompanied by shifts in carbon allocation and phenological changes in woody angiosperms, the timing of which can have broad implications for species distributions, interactions and ecosystem processes. During critical transitions from autumn to winter and winter to spring, physiological and anatomical changes within the phloem could impose a physical limit on the ability of woody angiosperms to transport carbon and signals. There is a paucity of the literature that addresses tree (floral or foliar) phenology, seasonal phloem anatomy and seasonal phloem physiology together, so our knowledge of how carbon transport could fluctuate seasonally, especially in temperate climates is limited. We review phloem phenology focussing on how sieve element anatomy and phloem sap flow could affect carbon availability throughout the year with a focus on winter. To investigate whether flow is possible in the winter, we construct a simple model of phloem sap flow and investigate how changes to the sap concentration, pressure gradient and sieve plate pores could influence flow during the winter. Our model suggests that phloem transport in some species could occur year-round, even in winter, but current methods for measuring all the parameters surrounding phloem sap flow make it difficult to test this hypothesis. We highlight outstanding questions that remain about phloem functionality in the winter and emphasize the need for new methods to address gaps in our knowledge about phloem function.
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Affiliation(s)
- Dustin M Ray
- Department of Biology, University of Minnesota Duluth, Duluth, MN 55811, USA
| | - Jessica A Savage
- Department of Biology, University of Minnesota Duluth, Duluth, MN 55811, USA
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12
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Barceló-Anguiano M, Hormaza JI, Losada JM. Conductivity of the phloem in mango (Mangifera indica L.). HORTICULTURE RESEARCH 2021; 8:150. [PMID: 34193860 PMCID: PMC8245510 DOI: 10.1038/s41438-021-00584-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/23/2021] [Accepted: 05/20/2021] [Indexed: 06/13/2023]
Abstract
Mango (Mangifera indica L., Anacardiaceae), the fifth most consumed fruit worldwide, is one of the most important fruit crops in tropical regions, but its vascular anatomy is quite unexplored. Previous studies examined the xylem structure in the stems of mango, but the anatomy of the phloem has remained elusive, leaving the long-distance transport of photoassimilates understudied. We combined fluorescence and electron microscopy to evaluate the structure of the phloem tissue in the tapering branches of mango trees, and used this information to describe the hydraulic conductivity of its sieve tube elements following current models of fluid transport in trees. We revealed that the anatomy of the phloem changes from current year branches, where it was protected by pericyclic fibres, to older ones, where the lack of fibres was concomitant with laticiferous canals embedded in the phloem tissue. Callose was present in the sieve plates, but also in the walls of the phloem sieve cells, making them discernible from other phloem cells. A scaling geometry of the sieve tube elements-including the number of sieve areas and the pore size across tapering branches-resulted in an exponential conductivity towards the base of the tree. These evaluations in mango fit with previous measurements of the phloem architecture in the stems of forest trees, suggesting that, despite agronomic management, the phloem sieve cells scale with the tapering branches. The pipe model theory applied to the continuous tubing system of the phloem appears as a good approach to understand the hydraulic transport of photoassimilates in fruit trees.
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Affiliation(s)
- Miguel Barceló-Anguiano
- Instituto de Hortofruticultura Subtropical y Mediterránea La Mayora (IHSM La Mayora-CSIC-UMA), Avda Dr. Wienberg s/n. 29750, Algarrobo-Costa, Málaga, Spain
| | - José I Hormaza
- Instituto de Hortofruticultura Subtropical y Mediterránea La Mayora (IHSM La Mayora-CSIC-UMA), Avda Dr. Wienberg s/n. 29750, Algarrobo-Costa, Málaga, Spain
| | - Juan M Losada
- Instituto de Hortofruticultura Subtropical y Mediterránea La Mayora (IHSM La Mayora-CSIC-UMA), Avda Dr. Wienberg s/n. 29750, Algarrobo-Costa, Málaga, Spain.
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Liesche J, Vincent C, Han X, Zwieniecki M, Schulz A, Gao C, Bravard R, Marker S, Bohr T. The mechanism of sugar export from long conifer needles. THE NEW PHYTOLOGIST 2021; 230:1911-1924. [PMID: 33638181 DOI: 10.1111/nph.17302] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Accepted: 02/17/2021] [Indexed: 06/12/2023]
Abstract
The green leaves of plants are optimised for carbon fixation and the production of sugars, which are used as central units of carbon and energy throughout the plant. However, there are physical limits to this optimisation that remain insufficiently understood. Here, quantitative anatomical analysis combined with mathematical modelling and sugar transport rate measurements were used to determine how effectively sugars are exported from the needle-shaped leaves of conifers in relation to leaf length. Mathematical modelling indicated that phloem anatomy constrains sugar export in long needles. However, we identified two mechanisms by which this constraint is overcome, even in needles longer than 20 cm: (1) the grouping of transport conduits, and (2) a shift in the diurnal rhythm of sugar metabolism and export in needle tips. The efficiency of sugar transport in the phloem can have a significant influence on leaf function. The constraints on sugar export described here for conifer needles are likely to also be relevant in other groups of plants, such as grasses and angiosperm trees.
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Affiliation(s)
- Johannes Liesche
- College of Life Sciences & Biomass Energy Center for Arid and Semi-arid Lands, Northwest A&F University, Taicheng Road 3, Yangling, 712100, China
- Cluster of Excellence on Plant Sciences (CEPLAS), Heinrich-Heine-Universität Düsseldorf, Universitätsstraße 1, Düsseldorf, 40225, Germany
| | - Christopher Vincent
- Department of Horticultural Sciences, University of Florida, 700 Experiment Station Road, Lake Alfred, FL, 33850, USA
| | - Xiaoyu Han
- College of Life Sciences & Biomass Energy Center for Arid and Semi-arid Lands, Northwest A&F University, Taicheng Road 3, Yangling, 712100, China
| | - Maciej Zwieniecki
- Department of Plant Sciences, University of California, Davis One Shields Avenue, Davis, CA, 95616, USA
| | - Alexander Schulz
- Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, Frederiksberg, 1871, Denmark
| | - Chen Gao
- Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, Frederiksberg, 1871, Denmark
| | - Rodrigue Bravard
- Department of Physics, Technical University of Denmark, Kgs. Lyngby, DK-2800, Denmark
| | - Sean Marker
- Department of Physics, Technical University of Denmark, Kgs. Lyngby, DK-2800, Denmark
| | - Tomas Bohr
- Department of Physics, Technical University of Denmark, Kgs. Lyngby, DK-2800, Denmark
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Peters WS, Jensen KH, Stone HA, Knoblauch M. Plasmodesmata and the problems with size: Interpreting the confusion. JOURNAL OF PLANT PHYSIOLOGY 2021; 257:153341. [PMID: 33388666 DOI: 10.1016/j.jplph.2020.153341] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Revised: 12/04/2020] [Accepted: 12/07/2020] [Indexed: 05/14/2023]
Abstract
Plant tissues exhibit a symplasmic organization; the individual protoplasts are connected to their neighbors via cytoplasmic bridges that extend through pores in the cell walls. These bridges may have diameters of a micrometer or more, as in the sieve pores of the phloem, but in most cell types they are smaller. Historically, botanists referred to cytoplasmic bridges of all sizes as plasmodesmata. The meaning of the term began to shift when the transmission electron microscope (TEM) became the preferred tool for studying these structures. Today, a plasmodesma is widely understood to be a 'nano-scale' pore. Unfortunately, our understanding of these nanoscopic channels suffers from methodological limitations. This is exemplified by the fact that state-of-the-art EM techniques appear to reveal plasmodesmal pore structures that are much smaller than the tracer molecules known to diffuse through these pores. In general, transport processes in pores that have dimensions in the size range of the transported molecules are governed by different physical parameters than transport process in the macroscopic realm. This can lead to unexpected effects, as experience in nanofluidic technologies demonstrates. Our discussion of problems of size in plasmodesma research leads us to conclude that the field will benefit from technomimetic reasoning - the utilization of concepts developed in applied nanofluidics for the interpretation of biological systems.
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Affiliation(s)
- Winfried S Peters
- School of Biological Sciences, Washington State University, Pullman, WA, 99164, USA; Department of Biology, Purdue University Fort Wayne, Fort Wayne, IN, 46805, USA.
| | - Kaare H Jensen
- Department of Physics, Technical University of Denmark, DK-2800 Kgs., Lyngby, Denmark.
| | - Howard A Stone
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ, 08544, USA.
| | - Michael Knoblauch
- School of Biological Sciences, Washington State University, Pullman, WA, 99164, USA.
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15
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Clerx LE, Rockwell FE, Savage JA, Holbrook NM. Ontogenetic scaling of phloem sieve tube anatomy and hydraulic resistance with tree height in Quercus rubra. AMERICAN JOURNAL OF BOTANY 2020; 107:852-863. [PMID: 32468597 DOI: 10.1002/ajb2.1481] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/24/2019] [Accepted: 03/12/2020] [Indexed: 06/11/2023]
Abstract
PREMISE The dimensions of phloem sieve elements have been shown to vary as a function of tree height, decreasing hydraulic resistance as the transport pathway lengthens. However, little is known about ontogenetic patterns of sieve element scaling. Here we examine within a single species (Quercus rubra) how decreases in hydraulic resistance with distance from the plant apex are mediated by overall plant size. METHODS We sampled and imaged phloem tissue at multiple heights along the main stem and in the live crown of four size classes of trees using fluorescence and scanning electron microscopy. Sieve element length and radius, the number of sieve areas per compound plate, pore number, and pore radius were used to calculate total hydraulic resistance at each sampling location. RESULTS Sieve element length varied with tree size, while sieve element radius, sieve pore radius, and the number of sieve areas per compound plate varied with sampling position. When data from all size classes were aggregated, all four variables followed a power-law trend with distance from the top of the tree. The net effect of these ontogenetic scalings was to make total hydraulic sieve tube resistance independent of tree height from 0.5 to over 20 m. CONCLUSIONS Sieve element development responded to two pieces of information, tree size and distance from the apex, in a manner that conserved total sieve tube resistance across size classes. A further differentiated response between the phloem in the live crown and in the main stem is also suggested.
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Affiliation(s)
- Laura E Clerx
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, 02138, USA
| | - Fulton E Rockwell
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, 02138, USA
| | - Jessica A Savage
- Department of Biology, University of Minnesota, Duluth, MN, 55812, USA
| | - N Michele Holbrook
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, 02138, USA
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16
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Gao C, Liu X, De Storme N, Jensen KH, Xu Q, Yang J, Liu X, Chen S, Martens HJ, Schulz A, Liesche J. Directionality of Plasmodesmata-Mediated Transport in Arabidopsis Leaves Supports Auxin Channeling. Curr Biol 2020; 30:1970-1977.e4. [DOI: 10.1016/j.cub.2020.03.014] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Revised: 02/09/2020] [Accepted: 03/06/2020] [Indexed: 01/12/2023]
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Su Y, Ashworth VETM, Geitner NK, Wiesner MR, Ginnan N, Rolshausen P, Roper C, Jassby D. Delivery, Fate, and Mobility of Silver Nanoparticles in Citrus Trees. ACS NANO 2020; 14:2966-2981. [PMID: 32141736 DOI: 10.1021/acsnano.9b07733] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Crop disease control is crucial for the sustainable development of agriculture, with recent advances in nanotechnology offering a promising solution to this pressing problem. However, the efficacy of nanoparticle (NP) delivery methods has not been fully explored, and knowledge regarding the fate and mobility of NPs within trees is still largely unknown. In this study, we evaluate the efficiency of NP delivery methods and investigate the mobility and distribution of NPs with different surface coatings (citrate (Ct), polyvinylpyrrolidone (PVP), and gum Arabic (GA)) within Mexican lime citrus trees. In contrast to the limited delivery efficiency reported for foliar and root delivery methods, petiole feeding and trunk injection are able to deliver a large amount of NPs into trees, although petiole feeding takes much longer time than trunk injection (7 days vs 2 h in citrus trees). Once NPs enter plants, steric repulsive interactions between NPs and conducting tube surfaces are predicted to facilitate NP transport throughout the plant. Compared to PVP and Ct, GA is highly effective in inhibiting the aggregation of NPs in synthetic sap and enhancing the mobility of NPs in trees. Over a 7 day experimental period, the majority of the Ag recovered from trees (10 mL, 10 ppm GA-AgNP suspension) remain throughout the trunk (81.0% on average), with a considerable amount in the roots (11.7% on average), some in branches (4.4% on average), and a limited amount in leaves (2.9% on average). Furthermore, NP concentrations during injection and tree incubation time postinjection are found to impact the distribution of Ag in tree. We also present evidence for a transport pathway that allows NPs to move from the xylem to the phloem, which disperses the NPs throughout the plant architecture, including to the roots.
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Affiliation(s)
- Yiming Su
- Department of Civil and Environmental Engineering, University of California, Los Angeles, California 90095, United States
| | - Vanessa E T M Ashworth
- Department of Botany and Plant Sciences, University of California, Riverside, California 92521, United States
| | - Nicholas K Geitner
- Department of Civil and Environmental Engineering, Duke University, Durham, North Carolina 27708, United States
| | - Mark R Wiesner
- Department of Civil and Environmental Engineering, Duke University, Durham, North Carolina 27708, United States
| | - Nichole Ginnan
- Department of Plant Pathology, University of California, Riverside, California 92521, United States
| | - Philippe Rolshausen
- Department of Botany and Plant Sciences, University of California, Riverside, California 92521, United States
| | - Caroline Roper
- Department of Plant Pathology, University of California, Riverside, California 92521, United States
| | - David Jassby
- Department of Civil and Environmental Engineering, University of California, Los Angeles, California 90095, United States
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Aliche EB, Prusova-Bourke A, Ruiz-Sanchez M, Oortwijn M, Gerkema E, Van As H, Visser RGF, van der Linden CG. Morphological and physiological responses of the potato stem transport tissues to dehydration stress. PLANTA 2020; 251:45. [PMID: 31915930 DOI: 10.1007/s00425-019-03336-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2019] [Accepted: 12/24/2019] [Indexed: 05/21/2023]
Abstract
Adaptation of the xylem under dehydration to smaller sized vessels and the increase in xylem density per stem area facilitate water transport during water-limiting conditions, and this has implications for assimilate transport during drought. The potato stem is the communication and transport channel between the assimilate-exporting source leaves and the terminal sink tissues of the plant. During environmental stress conditions like water scarcity, which adversely affect the performance (canopy growth and tuber yield) of the potato plant, the response of stem tissues is essential, however, still understudied. In this study, we investigated the response of the stem tissues of cultivated potato grown in the greenhouse to dehydration using a multidisciplinary approach including physiological, biochemical, morphological, microscopic, and magnetic resonance imaging techniques. We observed the most significant effects of water limitation in the lower stem regions of plants. The light microscopy analysis of the potato stem sections revealed that plants exposed to this particular dehydration stress have higher total xylem density per unit area than control plants. This increase in the total xylem density was accompanied by an increase in the number of narrow-diameter xylem vessels and a decrease in the number of large-diameter xylem vessels. Our MRI approach revealed a diurnal rhythm of xylem flux between day and night, with a reduction in xylem flux that is linked to dehydration sensitivity. We also observed that sink strength was the main driver of assimilate transport through the stem in our data set. These findings may present potential breeding targets for drought tolerance in potato.
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Affiliation(s)
- Ernest B Aliche
- Plant Breeding, Wageningen University and Research, Droevendaalsesteeg 1, 6708 PB, Wageningen, The Netherlands
- Graduate School Experimental Plant Sciences, Droevendaalsesteeg 1, 6708 PB, Wageningen, The Netherlands
| | - Alena Prusova-Bourke
- Laboratory of Biophysics, Wageningen University and Research, Stippeneng 4, 6708 WE, Wageningen, The Netherlands
| | - Mariam Ruiz-Sanchez
- Plant Breeding, Wageningen University and Research, Droevendaalsesteeg 1, 6708 PB, Wageningen, The Netherlands
| | - Marian Oortwijn
- Plant Breeding, Wageningen University and Research, Droevendaalsesteeg 1, 6708 PB, Wageningen, The Netherlands
| | - Edo Gerkema
- Laboratory of Biophysics, Wageningen University and Research, Stippeneng 4, 6708 WE, Wageningen, The Netherlands
| | - Henk Van As
- Laboratory of Biophysics, Wageningen University and Research, Stippeneng 4, 6708 WE, Wageningen, The Netherlands
| | - Richard G F Visser
- Plant Breeding, Wageningen University and Research, Droevendaalsesteeg 1, 6708 PB, Wageningen, The Netherlands
| | - C Gerard van der Linden
- Plant Breeding, Wageningen University and Research, Droevendaalsesteeg 1, 6708 PB, Wageningen, The Netherlands.
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19
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Deinum EE, Mulder BM, Benitez-Alfonso Y. From plasmodesma geometry to effective symplasmic permeability through biophysical modelling. eLife 2019; 8:49000. [PMID: 31755863 PMCID: PMC6994222 DOI: 10.7554/elife.49000] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2019] [Accepted: 11/16/2019] [Indexed: 12/12/2022] Open
Abstract
Regulation of molecular transport via intercellular channels called plasmodesmata (PDs) is important for both coordinating developmental and environmental responses among neighbouring cells, and isolating (groups of) cells to execute distinct programs. Cell-to-cell mobility of fluorescent molecules and PD dimensions (measured from electron micrographs) are both used as methods to predict PD transport capacity (i.e., effective symplasmic permeability), but often yield very different values. Here, we build a theoretical bridge between both experimental approaches by calculating the effective symplasmic permeability from a geometrical description of individual PDs and considering the flow towards them. We find that a dilated central region has the strongest impact in thick cell walls and that clustering of PDs into pit fields strongly reduces predicted permeabilities. Moreover, our open source multi-level model allows to predict PD dimensions matching measured permeabilities and add a functional interpretation to structural differences observed between PDs in different cell walls.
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Affiliation(s)
- Eva E Deinum
- Mathematical and statistical methods (Biometris), Wageningen University, Wageningen, Netherlands
| | - Bela M Mulder
- Living Matter Department, Institute AMOLF, Amsterdam, Netherlands.,Laboratory of Cell Biology, Wageningen University, Wageningen, Netherlands
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20
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Epron D, Dannoura M, Ishida A, Kosugi Y. Estimation of phloem carbon translocation belowground at stand level in a hinoki cypress stand. TREE PHYSIOLOGY 2019; 39:320-331. [PMID: 29474703 DOI: 10.1093/treephys/tpy016] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2017] [Revised: 01/15/2018] [Accepted: 01/27/2018] [Indexed: 06/08/2023]
Abstract
At stand level, carbon translocation in tree stems has to match canopy photosynthesis and carbohydrate requirements to sustain growth and the physiological activities of belowground sinks. This study applied the Hagen-Poiseuille equation to the pressure-flow hypothesis to estimate phloem carbon translocation and evaluate what percentage of canopy photosynthate can be transported belowground in a hinoki cypress (Chamaecyparis obtusa Sieb. et Zucc.) stand. An anatomical study revealed that, in contrast to sieve cell density, conductive phloem thickness and sieve cell hydraulic diameter at 1.3 m in height increased with increasing tree diameter, as did the concentration of soluble sugars in the phloem sap. At tree level, hydraulic conductivity increased by two orders of magnitude from the smallest to the largest trees in the stand, resulting in a stand-level hydraulic conductance of 1.7 × 10-15 m Pa-1 s-1. The osmotic potential of the sap extracted from the inner bark was -0.75 MPa. Assuming that phloem water potential equalled foliage water potential at predawn, the turgor pressure in the phloem at 1.3 m in height was estimated at 0.22 MPa, 0.59 MPa lower than values estimated in the foliage. With this maximal turgor pressure gradient, which would be lower during day-time when foliage water potential drops, the estimated stand-level rate of carbon translocation was 2.0 gC m-2 day-1 (30% of daily gross canopy photosynthesis), at a time of the year when aboveground growth and related respiration is thought to consume a large fraction of photosynthate, at the expense of belowground activity. Despite relying on some assumptions and approximations, this approach, when coupled with measurements of canopy photosynthesis, may further be used to provide qualitative insight into the seasonal dynamics of belowground carbon allocation.
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Affiliation(s)
- Daniel Epron
- Université de Lorraine, INRA, UMR SILVA, Faculté des Sciences et Technologies, Vandœuvre-lès-Nancy, France
- Kyoto University, Laboratory of Ecosystem Production and Dynamics, Graduate School of Global Environmental Studies, Kyoto, Japan
| | - Masako Dannoura
- Kyoto University, Laboratory of Ecosystem Production and Dynamics, Graduate School of Global Environmental Studies, Kyoto, Japan
- Kyoto University, Laboratory of Forest Utilization, Graduate School of Agriculture, Kyoto, Japan
| | - Atsushi Ishida
- Kyoto University, Center for Ecological Research, Otsu, Shiga, Japan
| | - Yoshiko Kosugi
- Kyoto University, Laboratory of Forest Hydrology, Graduate School of Agriculture, Kyoto, Japan
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21
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Stanfield RC, Schulte PJ, Randolph KE, Hacke UG. Computational models evaluating the impact of sieve plates and radial water exchange on phloem pressure gradients. PLANT, CELL & ENVIRONMENT 2019; 42:466-479. [PMID: 30074610 DOI: 10.1111/pce.13414] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2018] [Accepted: 07/20/2018] [Indexed: 05/06/2023]
Abstract
The sugar conducting phloem in angiosperms is a high resistance pathway made up of sieve elements bounded by sieve plates. The high resistance generated by sieve plates may be a trade-off for promoting quick sealing in the event of injury. However, previous modeling efforts have demonstrated a wide variation in the contribution of sieve plates towards total sieve tube resistance. In the current study, we generated high resolution scanning electron microscope images of sieve plates from balsam poplar and integrated them into a mathematical model using Comsol Multiphysics software. We found that sieve plates contribute upwards of 85% towards total sieve tube resistance. Utilizing the Navier-Stokes equations, we found that oblong pores may create over 50% more resistance in comparison with round pores of the same area. Although radial water flows in phloem sieve tubes have been previously considered, their impact on alleviating pressure gradients has not been fully studied. Our novel simulations find that radial water flow can reduce pressure requirements by half in comparison with modeled sieve tubes with no radial permeability. We discuss the implication that sieve tubes may alleviate pressure requirements to overcome high resistances by regulating their membrane permeability along the entire transport pathway.
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Affiliation(s)
- Ryan C Stanfield
- Department of Renewable Resources, University of Alberta, Edmonton, Alberta, Canada
| | - Paul J Schulte
- School of Life Sciences, University of Nevada-Las Vegas, Las Vegas, Nevada
| | - Katie E Randolph
- School of Life Sciences, University of Nevada-Las Vegas, Las Vegas, Nevada
| | - Uwe G Hacke
- Department of Renewable Resources, University of Alberta, Edmonton, Alberta, Canada
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22
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Konrad W, Katul G, Roth-Nebelsick A, Jensen KH. Xylem functioning, dysfunction and repair: a physical perspective and implications for phloem transport. TREE PHYSIOLOGY 2019; 39:243-261. [PMID: 30299503 DOI: 10.1093/treephys/tpy097] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Revised: 07/31/2018] [Accepted: 08/08/2018] [Indexed: 05/02/2023]
Abstract
Xylem and phloem are the two main conveyance systems in plants allowing exchanges of water and carbohydrates between roots and leaves. While each system has been studied in isolation for well over a century, the coupling and coordination between them remains the subject of inquiry and active research and frames the scope of the review here. Using a set of balance equations, hazards of bubble formation and their role in shaping xylem pressure and its corollary impact on phloem pressure and sugar transport are featured. The behavior of an isolated and freely floating air bubble within the xylem is first analyzed so as to introduce key principles such as the Helmholtz free energy and its links to embryonic bubble sizes. These principles are extended by considering bubbles filled with water vapor and air arising from air seeding. Using this framework, key results about stability and hazards of bubbles in contact with xylem walls are discussed. A chemical equilibrium between phloem and xylem systems is then introduced to link xylem and osmotic pressures. The consequences of such a link for sugar concentration needed to sustain efficient phloem transport by osmosis in the loading zone is presented. Catastrophic cases where phloem dysfunction occurs are analyzed in terms of xylem function and its vulnerability to cavitation. A link between operating pressures in the soil system bounded by field capacity and wilting points and maintenance of phloem functioning are discussed as conjectures to be tested in the future.
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Affiliation(s)
- Wilfried Konrad
- Department of Geosciences, University of Tübingen, Hoelderlinstrasse 12, Tübingen, Germany
- Institute of Botany, Technische Universität Dresden, Zellescher Weg 20b, Dresden, Germany
| | - Gabriel Katul
- Nicholas School of the Environment and Earth Sciences, Levine Science Research Center, Duke University, Durham, NC, USA
| | - Anita Roth-Nebelsick
- Deptartment of Palaeontology, State Museum of Natural History Stuttgart, Rosenstein 1, Stuttgart, Germany
| | - Kaare H Jensen
- Department of Physics, Technical University of Denmark, Fysikvej Building 309, Kgs. Lyngby, Denmark
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23
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Dannoura M, Epron D, Desalme D, Massonnet C, Tsuji S, Plain C, Priault P, Gérant D. The impact of prolonged drought on phloem anatomy and phloem transport in young beech trees. TREE PHYSIOLOGY 2019; 39:201-210. [PMID: 29931112 DOI: 10.1093/treephys/tpy070] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Revised: 05/04/2018] [Accepted: 05/18/2018] [Indexed: 06/08/2023]
Abstract
Phloem failure has recently been recognized as one of the mechanisms causing tree mortality under drought, though direct evidence is still lacking. We combined 13C pulse-labelling of 8-year-old beech trees (Fagus sylvatica L.) growing outdoors in a nursery with an anatomical study of the phloem tissue in their stems to examine how drought alters carbon transport and phloem transport capacity. For the six trees under drought, predawn leaf water potential ranged from -0.7 to -2.4 MPa, compared with an average of -0.2 MPa in five control trees with no water stress. We also observed a longer residence time of excess 13C in the foliage and the phloem sap in trees under drought compared with controls. Compared with controls, excess 13C in trunk respiration peaked later in trees under moderate drought conditions and showed no decline even after 4 days under more severe drought conditions. We estimated higher phloem sap viscosity in trees under drought. We also observed much smaller sieve-tube radii in all drought-stressed trees, which led to lower sieve-tube conductivity and lower phloem conductance in the tree stem. We concluded that prolonged drought affected phloem transport capacity through a change in anatomy and that the slowdown of phloem transport under drought likely resulted from a reduced driving force due to lower hydrostatic pressure between the source and sink organs.
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Affiliation(s)
- Masako Dannoura
- Université de Lorraine, AgroParisTech, INRA, UMR Silva, Faculté des Sciences et Technologies, Nancy, France
- Laboratory of Ecosystem Production and Dynamics, Graduate School of Global Environmental Studies, Kyoto University, Kyoto, Japan
- Laboratory of Forest Utilization, Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | - Daniel Epron
- Université de Lorraine, AgroParisTech, INRA, UMR Silva, Faculté des Sciences et Technologies, Nancy, France
| | - Dorine Desalme
- Université de Lorraine, AgroParisTech, INRA, UMR Silva, Faculté des Sciences et Technologies, Nancy, France
| | - Catherine Massonnet
- Université de Lorraine, AgroParisTech, INRA, UMR Silva, Faculté des Sciences et Technologies, Nancy, France
| | - Shoko Tsuji
- Laboratory of Ecosystem Production and Dynamics, Graduate School of Global Environmental Studies, Kyoto University, Kyoto, Japan
| | - Caroline Plain
- Université de Lorraine, AgroParisTech, INRA, UMR Silva, Faculté des Sciences et Technologies, Nancy, France
| | - Pierrick Priault
- Université de Lorraine, AgroParisTech, INRA, UMR Silva, Faculté des Sciences et Technologies, Nancy, France
| | - Dominique Gérant
- Université de Lorraine, AgroParisTech, INRA, UMR Silva, Faculté des Sciences et Technologies, Nancy, France
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Losada JM, Holbrook NM. Scaling of phloem hydraulic resistance in stems and leaves of the understory angiosperm shrub Illicium parviflorum. AMERICAN JOURNAL OF BOTANY 2019; 106:244-259. [PMID: 30793276 DOI: 10.1002/ajb2.1241] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Accepted: 12/05/2018] [Indexed: 06/09/2023]
Abstract
PREMISE OF THE STUDY Recent studies in canopy-dominant trees revealed axial scaling of phloem structure. However, whether this pattern is found in woody plants of the understory, the environment of most angiosperms from the ANA grade (Amborellales-Nymphaeales-Austrobaileyales), is unknown. METHODS We used seedlings and adult plants of the understory tropical shrub Illicium parviflorum, a member of the lineage Austrobaileyales, to explore the anatomy and physiology of the phloem in their aerial parts, including changes through ontogeny. KEY RESULTS Adult plants maintain a similar proportion of phloem tissue across stem diameters, but larger conduit dimensions and number cause the hydraulic resistance of the phloem to decrease toward the base of the plant. Small sieve plate pores resulted in an overall higher sieve tube hydraulic resistance than has been reported in other woody angiosperms. Sieve elements increase in size from minor to major leaf veins, but were shorter and narrower in petioles. The low carbon assimilation rates of seedlings and mature plants contrasted with a 3-fold higher phloem sap velocity in seedlings, suggesting that phloem transport velocity is modulated through ontogeny. CONCLUSIONS The overall architecture of the phloem tissue in this understory angiosperm shrub scales in a manner consistent with taller trees that make up the forest canopy. Thus, the evolution of larger sieve plate pores in canopy-dominant trees may have played a key role in allowing woody angiosperms to extend beyond their understory origins.
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Affiliation(s)
- Juan M Losada
- Department of Organismic and Evolutionary Biology, Harvard University, 16 Divinity Avenue, Cambridge, MA, 02138, USA
- Arnold Arboretum of Harvard University, 1300 Centre St., Boston, MA, 02130, USA
| | - N Michele Holbrook
- Department of Organismic and Evolutionary Biology, Harvard University, 16 Divinity Avenue, Cambridge, MA, 02138, USA
- Arnold Arboretum of Harvard University, 1300 Centre St., Boston, MA, 02130, USA
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Kalmbach L, Helariutta Y. Sieve Plate Pores in the Phloem and the Unknowns of Their Formation. PLANTS (BASEL, SWITZERLAND) 2019; 8:E25. [PMID: 30678196 PMCID: PMC6409547 DOI: 10.3390/plants8020025] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/07/2018] [Revised: 01/17/2019] [Accepted: 01/19/2019] [Indexed: 01/13/2023]
Abstract
Sieve pores of the sieve plates connect neighboring sieve elements to form the conducting sieve tubes of the phloem. Sieve pores are critical for phloem function. From the 1950s onwards, when electron microscopes became increasingly available, the study of their formation had been a pillar of phloem research. More recent work on sieve elements instead has largely focused on sieve tube hydraulics, phylogeny, and eco-physiology. Additionally, advanced molecular and genetic tools available for the model species Arabidopsis thaliana helped decipher several key regulatory mechanisms of early phloem development. Yet, the downstream differentiation processes which form the conductive sieve tube are still largely unknown, and our understanding of sieve pore formation has only moderately progressed. Here, we summarize our current knowledge on sieve pore formation and present relevant recent advances in related fields such as sieve element evolution, physiology, and plasmodesmata formation.
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Affiliation(s)
- Lothar Kalmbach
- The Sainsbury Laboratory, University of Cambridge, Bateman Street, Cambridge CB2 1LR, UK.
| | - Ykä Helariutta
- The Sainsbury Laboratory, University of Cambridge, Bateman Street, Cambridge CB2 1LR, UK.
- Institute of Biotechnology, University of Helsinki, 00014 Helsinki, Finland.
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Jensen KH. Modeling the Hydraulic Conductivity of Phloem Sieve Elements. Methods Mol Biol 2019; 2014:339-344. [PMID: 31197807 DOI: 10.1007/978-1-4939-9562-2_26] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Phloem transport of photoassimilates affects nearly all aspects of plant life, from growth to reproduction. This chapter summarizes mathematical techniques to quantify the impact of sieve element anatomy on phloem transport processes.
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Affiliation(s)
- Kaare H Jensen
- Department of Physics, Technical University of Denmark, Kgs. Lyngby, Denmark.
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Tixier A, Orozco J, Roxas AA, Earles JM, Zwieniecki MA. Diurnal Variation in Nonstructural Carbohydrate Storage in Trees: Remobilization and Vertical Mixing. PLANT PHYSIOLOGY 2018; 178:1602-1613. [PMID: 30366979 PMCID: PMC6288742 DOI: 10.1104/pp.18.00923] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Accepted: 10/18/2018] [Indexed: 05/19/2023]
Abstract
Nonstructural carbohydrate (NSC) storage plays a critical role in tree function and survival, but understanding and predicting local NSC storage dynamics is challenging because NSC storage pools are dispersed throughout the complex architecture of trees and continuously exchange carbon between source and sink organs at different time scales. To address these knowledge gaps, characterization and understanding of NSC diel variation are necessary. Here, we analyzed diurnal NSC dynamics in the overall architecture of almond (Prunus dulcis) trees. We also analyzed the allocation of newly assimilated carbon using isotopic labeling. We show that both components of NSC (i.e. soluble carbohydrates and starch) are highly dynamic at the diurnal time scale and that these trends are influenced by tissue type, age, and/or position within the canopy. In leaves, starch reserves can be depleted completely during the night, while woody tissue starch levels may vary by more than 50% over a daily cycle. Recently assimilated carbon showed a dispersed downward allocation across the entire tree. NSC diurnal fluctuations within the tree's structure in combination with dispersed carbon allocation patterns provide evidence for the presence of vertical mixing and suggest that the xylem acts as a secondary NSC redistribution pathway.
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Affiliation(s)
- Aude Tixier
- Department of Plant Sciences, University of California, Davis, California 95616
| | - Jessica Orozco
- Department of Plant Sciences, University of California, Davis, California 95616
| | - Adele Amico Roxas
- Department of Plant Sciences, University of California, Davis, California 95616
| | - J Mason Earles
- Yale School of Forestry and Environmental Studies, New Haven, Connecticut 06511
| | - Maciej A Zwieniecki
- Department of Plant Sciences, University of California, Davis, California 95616
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28
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Jensen KH. Phloem physics: mechanisms, constraints, and perspectives. CURRENT OPINION IN PLANT BIOLOGY 2018; 43:96-100. [PMID: 29660560 DOI: 10.1016/j.pbi.2018.03.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2017] [Revised: 03/11/2018] [Accepted: 03/13/2018] [Indexed: 05/17/2023]
Abstract
Plants have evolved specialized vascular tissues for the distribution of energy, water, nutrients, and for communication. The phloem transports sugars from photosynthetic source regions (e.g. mature leaves) to sugar sinks (e.g. developing tissues such as buds, flowers, roots). Moreover, chemical signals such as hormones, RNAs and proteins also move in the phloem. Basic physical processes strongly limit phloem anatomy and function. This paper provides an overview of recent research and perspectives on phloem biomechanics and the physical constraints relevant to sugar transport in plants.
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Affiliation(s)
- Kaare H Jensen
- Department of Physics, Technical University of Denmark, Fysikvej, DK-2800, Kgs. Lyngby, Denmark.
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29
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Knox K, Oparka K. Illuminating the translocation stream. CURRENT OPINION IN PLANT BIOLOGY 2018; 43:113-118. [PMID: 29729487 DOI: 10.1016/j.pbi.2018.03.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2017] [Revised: 03/14/2018] [Accepted: 03/21/2018] [Indexed: 06/08/2023]
Abstract
This review focuses on the recent development of a suite of fluorescent probes that can be used to trace phloem-transport rates in a range of diverse species. Some of these probes are loaded into the phloem by virtue of optimal physico-chemical properties for ion trapping in the high pH environment of the sieve element. However, others are clearly loaded by carrier-mediated transport, such as the blue-emitting probe, esculin, which is loaded into the Arabidopsis phloem by the sucrose transporter, AtSUC2, allowing it to be used as a surrogate for sucrose in phloem transport studies. We also describe additional chemical groups which, although highly charged (e.g. sulphonates), facilitate entry into the phloem. The addition of such 'mobilophores' to existing chemical groups has allowed us to expand the range of fluorophores that can be loaded into the phloem, and provides clues as to the nature of selectivity for phloem loading of xenobiotic compounds.
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Affiliation(s)
- Kirsten Knox
- Institute of Molecular Plant Sciences, Rutherford Building, School of Biological Sciences, Edinburgh University, Max Born Crescent, Kings Buildings, Edinburgh, UK.
| | - Karl Oparka
- Institute of Molecular Plant Sciences, Rutherford Building, School of Biological Sciences, Edinburgh University, Max Born Crescent, Kings Buildings, Edinburgh, UK
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30
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Raven JA. Evolution and palaeophysiology of the vascular system and other means of long-distance transport. Philos Trans R Soc Lond B Biol Sci 2018; 373:20160497. [PMID: 29254962 PMCID: PMC5745333 DOI: 10.1098/rstb.2016.0497] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/11/2017] [Indexed: 12/13/2022] Open
Abstract
Photolithotrophic growth on land using atmospheric CO2 inevitably involves H2O vapour loss. Embryophytes greater than or equal to 100 mm tall are homoiohydric and endohydric with mass flow of aqueous solution through the xylem in tracheophytes. Structural details in Rhynie sporophytes enable modelling of the hydraulics of H2O supply to the transpiring surface, and the potential for gas exchange with the Devonian atmosphere. Xylem carrying H2O under tension involves programmed cell death, rigid cell walls and embolism repair; fossils provide little evidence on these functions other than the presence of lignin. The phenylalanine ammonia lyase essential for lignin synthesis came from horizontal gene transfer. Rhynie plants lack endodermes, limiting regulation of the supply of soil nutrients to shoots. The transfer of organic solutes from photosynthetic sites to growing and storage tissues involves mass flow through phloem in extant tracheophytes. Rhynie plants show little evidence of phloem; possible alternatives for transport of organic solutes are discussed. Extant examples of the arbuscular mycorrhizas found in Rhynie plants exchange soil-derived nutrients (especially P) for plant-derived organic matter, involving bidirectional mass flow along the hyphae. The aquatic cyanobacteria and the charalean Palaeonitella at Rhynie also have long-distance (relative to the size of the organism) transport.This article is part of a discussion meeting issue 'The Rhynie cherts: our earliest terrestrial ecosystem revisited'.
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Affiliation(s)
- John A Raven
- Division of Plant Sciences, University of Dundee at the James Hutton Institute, Invergowrie, Dundee DD2 5DA, UK
- School of Biological Sciences, University of Western Australia, 35 Stirling Highway, Crawley, Western Australia 6009, Australia
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31
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Dietrich D, Pang L, Kobayashi A, Fozard JA, Boudolf V, Bhosale R, Antoni R, Nguyen T, Hiratsuka S, Fujii N, Miyazawa Y, Bae TW, Wells DM, Owen MR, Band LR, Dyson RJ, Jensen OE, King JR, Tracy SR, Sturrock CJ, Mooney SJ, Roberts JA, Bhalerao RP, Dinneny JR, Rodriguez PL, Nagatani A, Hosokawa Y, Baskin TI, Pridmore TP, De Veylder L, Takahashi H, Bennett MJ. Root hydrotropism is controlled via a cortex-specific growth mechanism. NATURE PLANTS 2017; 3:965-972. [PMID: 28481327 DOI: 10.1038/s41477-017-0064-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2017] [Accepted: 10/27/2017] [Indexed: 05/24/2023]
Abstract
Plants can acclimate by using tropisms to link the direction of growth to environmental conditions. Hydrotropism allows roots to forage for water, a process known to depend on abscisic acid (ABA) but whose molecular and cellular basis remains unclear. Here we show that hydrotropism still occurs in roots after laser ablation removed the meristem and root cap. Additionally, targeted expression studies reveal that hydrotropism depends on the ABA signalling kinase SnRK2.2 and the hydrotropism-specific MIZ1, both acting specifically in elongation zone cortical cells. Conversely, hydrotropism, but not gravitropism, is inhibited by preventing differential cell-length increases in the cortex, but not in other cell types. We conclude that root tropic responses to gravity and water are driven by distinct tissue-based mechanisms. In addition, unlike its role in root gravitropism, the elongation zone performs a dual function during a hydrotropic response, both sensing a water potential gradient and subsequently undergoing differential growth.
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Affiliation(s)
- Daniela Dietrich
- Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK
- Plant &Crop Sciences, School of Biosciences, University of Nottingham, Nottingham LE12 5RD, UK
| | - Lei Pang
- Graduate School of Life Sciences, Tohoku University, Sendai 980-8577, Japan
| | - Akie Kobayashi
- Graduate School of Life Sciences, Tohoku University, Sendai 980-8577, Japan
| | - John A Fozard
- Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK
| | - Véronique Boudolf
- Department of Plant Biotechnology and Bioinformatics, Ghent University, (Technologiepark 927), 9052 Ghent, Belgium
- VIB Center for Plant Systems Biology, (Technologiepark 927), 9052 Ghent, Belgium
| | - Rahul Bhosale
- Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK
- Plant &Crop Sciences, School of Biosciences, University of Nottingham, Nottingham LE12 5RD, UK
- Department of Plant Biotechnology and Bioinformatics, Ghent University, (Technologiepark 927), 9052 Ghent, Belgium
- VIB Center for Plant Systems Biology, (Technologiepark 927), 9052 Ghent, Belgium
| | - Regina Antoni
- Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK
| | - Tuan Nguyen
- Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK
- School of Computer Science, University of Nottingham, Nottingham NG8 1BB, UK
| | - Sotaro Hiratsuka
- Graduate School of Life Sciences, Tohoku University, Sendai 980-8577, Japan
| | - Nobuharu Fujii
- Graduate School of Life Sciences, Tohoku University, Sendai 980-8577, Japan
| | - Yutaka Miyazawa
- Faculty of Science, Yamagata University, Yamagata 990-8560, Japan
| | - Tae-Woong Bae
- Graduate School of Life Sciences, Tohoku University, Sendai 980-8577, Japan
| | - Darren M Wells
- Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK
- Plant &Crop Sciences, School of Biosciences, University of Nottingham, Nottingham LE12 5RD, UK
| | - Markus R Owen
- Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK
- Centre for Mathematical Medicine &Biology, University of Nottingham, Nottingham NG7 2RD, UK
| | - Leah R Band
- Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK
- Centre for Mathematical Medicine &Biology, University of Nottingham, Nottingham NG7 2RD, UK
| | - Rosemary J Dyson
- School of Mathematics, University of Birmingham, Birmingham B15 2TT, UK
| | - Oliver E Jensen
- Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK
- School of Mathematics, University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - John R King
- Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK
- Centre for Mathematical Medicine &Biology, University of Nottingham, Nottingham NG7 2RD, UK
| | - Saoirse R Tracy
- Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK
- Agricultural and Environmental Sciences, School of Biosciences, University of Nottingham, Nottingham LE12 5RD, UK
| | - Craig J Sturrock
- Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK
- Agricultural and Environmental Sciences, School of Biosciences, University of Nottingham, Nottingham LE12 5RD, UK
| | - Sacha J Mooney
- Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK
- Agricultural and Environmental Sciences, School of Biosciences, University of Nottingham, Nottingham LE12 5RD, UK
| | - Jeremy A Roberts
- Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK
- Plant &Crop Sciences, School of Biosciences, University of Nottingham, Nottingham LE12 5RD, UK
| | - Rishikesh P Bhalerao
- Department of Forest Genetics and Plant Physiology, SLU, S-901 83 Umea, Sweden
- College of Science, KSU, Riyadh, Saudi Arabia
| | - José R Dinneny
- Department of Plant Biology, Carnegie Institution for Science, 260 Panama Street, Stanford, California 94305, USA
| | - Pedro L Rodriguez
- Instituto de Biología Molecular y Celular de Plantas, Consejo Superior de Investigaciones Cientificas-Universidad Politecnica de Valencia, ES-46022 Valencia, Spain
| | - Akira Nagatani
- Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Yoichiroh Hosokawa
- Graduate School of Materials Science, Nara Institute of Science &Technology, Ikoma 630-0101, Japan
| | - Tobias I Baskin
- Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK
- Biology Department, University of Massachusetts, Amherst, Massachusetts 01003-9297, USA
| | - Tony P Pridmore
- Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK
- School of Computer Science, University of Nottingham, Nottingham NG8 1BB, UK
| | - Lieven De Veylder
- Department of Plant Biotechnology and Bioinformatics, Ghent University, (Technologiepark 927), 9052 Ghent, Belgium
- VIB Center for Plant Systems Biology, (Technologiepark 927), 9052 Ghent, Belgium
| | - Hideyuki Takahashi
- Graduate School of Life Sciences, Tohoku University, Sendai 980-8577, Japan
| | - Malcolm J Bennett
- Centre for Plant Integrative Biology, University of Nottingham, Nottingham LE12 5RD, UK
- Plant &Crop Sciences, School of Biosciences, University of Nottingham, Nottingham LE12 5RD, UK
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32
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Rademaker H, Zwieniecki MA, Bohr T, Jensen KH. Sugar export limits size of conifer needles. Phys Rev E 2017; 95:042402. [PMID: 28505712 DOI: 10.1103/physreve.95.042402] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2017] [Indexed: 06/07/2023]
Abstract
Plant leaf size varies by more than three orders of magnitude, from a few millimeters to over one meter. Conifer leaves, however, are relatively short and the majority of needles are no longer than 6 cm. The reason for the strong confinement of the trait-space is unknown. We show that sugars produced near the tip of long needles cannot be exported efficiently, because the pressure required to drive vascular flow would exceed the greatest available pressure (the osmotic pressure). This basic constraint leads to the formation of an inactive region of stagnant fluid near the needle tip, which does not contribute to sugar flow. Remarkably, we find that the size of the active part does not scale with needle length. We predict a single maximum needle size of 5 cm, in accord with data from 519 conifer species. This could help rationalize the recent observation that conifers have significantly smaller leaves than angiosperms, and provide a biophysical explanation for this intriguing difference between the two largest groups of plants.
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Affiliation(s)
- Hanna Rademaker
- Department of Physics, Technical University of Denmark, DK 2800 Kgs. Lyngby, Denmark
| | - Maciej A Zwieniecki
- Department of Plant Sciences, University of California at Davis, Davis, California 95616, USA
| | - Tomas Bohr
- Department of Physics, Technical University of Denmark, DK 2800 Kgs. Lyngby, Denmark
| | - Kaare H Jensen
- Department of Physics, Technical University of Denmark, DK 2800 Kgs. Lyngby, Denmark
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33
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Liesche J, Pace MR, Xu Q, Li Y, Chen S. Height-related scaling of phloem anatomy and the evolution of sieve element end wall types in woody plants. THE NEW PHYTOLOGIST 2017; 214:245-256. [PMID: 27935048 PMCID: PMC5347917 DOI: 10.1111/nph.14360] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2016] [Accepted: 10/18/2016] [Indexed: 05/05/2023]
Abstract
In the sieve elements (SEs) of the phloem, carbohydrates are transported throughout the whole plant from their site of production to sites of consumption or storage. SE structure, especially of the pore-rich end walls, has a direct effect on translocation efficiency. Differences in pore size and other features were interpreted as an evolutionary trend towards reduced hydraulic resistance. However, this has never been confirmed. Anatomical data of 447 species of woody angiosperms and gymnosperms were used for a phylogenetic analysis of end wall types, calculation of hydraulic resistance and correlation analysis with morphological and physiological variables. end wall types were defined according to pore arrangement: either grouped into a single area (simple) or into multiple areas along the end wall (compound). Convergent evolution of end wall types was demonstrated in woody angiosperms. In addition, an optimization of end wall resistance with plant height was discovered, but found to be independent of end wall type. While physiological factors also showed no correlation with end wall types, the number of sieve areas per end wall was found to scale with SE length. The results exclude the minimization of hydraulic resistance as evolutionary driver of different end wall types, contradicting this long-standing assumption. Instead, end wall type might depend on SE length.
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Affiliation(s)
- Johannes Liesche
- College of Life SciencesNorthwest A&F UniversityYangling712100China
- Biomass Energy Center for Arid and Semi‐arid landsNorthwest A&F UniversityYangling712100China
| | - Marcelo R. Pace
- Department of BotanyNational Museum of Natural HistorySmithsonian InstitutionWashingtonDC20013‐7012USA
| | - Qiyu Xu
- College of Life SciencesNorthwest A&F UniversityYangling712100China
- Biomass Energy Center for Arid and Semi‐arid landsNorthwest A&F UniversityYangling712100China
| | - Yongqing Li
- South China Botanical GardenChinese Academy of SciencesGuangzhou510650China
| | - Shaolin Chen
- College of Life SciencesNorthwest A&F UniversityYangling712100China
- Biomass Energy Center for Arid and Semi‐arid landsNorthwest A&F UniversityYangling712100China
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34
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Comtet J, Jensen KH, Turgeon R, Stroock AD, Hosoi AE. Passive phloem loading and long-distance transport in a synthetic tree-on-a-chip. NATURE PLANTS 2017; 3:17032. [PMID: 28319082 DOI: 10.1038/nplants.2017.32] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2016] [Accepted: 02/14/2017] [Indexed: 06/06/2023]
Abstract
Vascular plants rely on differences in osmotic pressure to export sugars from regions of synthesis (mature leaves) to sugar sinks (roots, fruits). In this process, known as Münch pressure flow, the loading of sugars from photosynthetic cells to the export conduit (the phloem) is crucial, as it sets the pressure head necessary to power long-distance transport. Whereas most herbaceous plants use active mechanisms to increase phloem sugar concentration above that of the photosynthetic cells, in most tree species, for which transport distances are largest, loading seems, counterintuitively, to occur by means of passive symplastic diffusion from the mesophyll to the phloem. Here, we use a synthetic microfluidic model of a passive loader to explore the non-linear dynamics that arise during export and determine the ability of passive loading to drive long-distance transport. We first demonstrate that in our device, the phloem concentration is set by the balance between the resistances to diffusive loading from the source and convective export through the phloem. Convection-limited export corresponds to classical models of Münch transport, where the phloem concentration is close to that of the source; in contrast, diffusion-limited export leads to small phloem concentrations and weak scaling of flow rates with hydraulic resistance. We then show that the effective regime of convection-limited export is predominant in plants with large transport resistances and low xylem pressures. Moreover, hydrostatic pressures developed in our synthetic passive loader can reach botanically relevant values as high as 10 bars. We conclude that passive loading is sufficient to drive long-distance transport in large plants, and that trees are well suited to take full advantage of passive phloem loading strategies.
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Affiliation(s)
- Jean Comtet
- MIT Mechanical Engineering, Cambridge, Massachusetts 02139, USA
| | - Kaare H Jensen
- Department of Physics, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
| | - Robert Turgeon
- Section of Plant Biology, Cornell University, Ithaca, New York 14853, USA
| | - Abraham D Stroock
- School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York 14853, USA
- Kavli Institute at Cornell for Nanoscale Science, Cornell University, Ithaca, New York 14853, USA
| | - A E Hosoi
- MIT Mechanical Engineering, Cambridge, Massachusetts 02139, USA
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35
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Ross-Elliott TJ, Jensen KH, Haaning KS, Wager BM, Knoblauch J, Howell AH, Mullendore DL, Monteith AG, Paultre D, Yan D, Otero S, Bourdon M, Sager R, Lee JY, Helariutta Y, Knoblauch M, Oparka KJ. Phloem unloading in Arabidopsis roots is convective and regulated by the phloem-pole pericycle. eLife 2017; 6. [PMID: 28230527 PMCID: PMC5365319 DOI: 10.7554/elife.24125] [Citation(s) in RCA: 140] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2016] [Accepted: 02/17/2017] [Indexed: 02/05/2023] Open
Abstract
In plants, a complex mixture of solutes and macromolecules is transported by the phloem. Here, we examined how solutes and macromolecules are separated when they exit the phloem during the unloading process. We used a combination of approaches (non-invasive imaging, 3D-electron microscopy, and mathematical modelling) to show that phloem unloading of solutes in Arabidopsis roots occurs through plasmodesmata by a combination of mass flow and diffusion (convective phloem unloading). During unloading, solutes and proteins are diverted into the phloem-pole pericycle, a tissue connected to the protophloem by a unique class of ‘funnel plasmodesmata’. While solutes are unloaded without restriction, large proteins are released through funnel plasmodesmata in discrete pulses, a phenomenon we refer to as ‘batch unloading’. Unlike solutes, these proteins remain restricted to the phloem-pole pericycle. Our data demonstrate a major role for the phloem-pole pericycle in regulating phloem unloading in roots. DOI:http://dx.doi.org/10.7554/eLife.24125.001 A mechanism called photosynthesis allows plants to use energy from sunlight to make sugars from carbon dioxide gas and water. These sugars can then be used as fuel, or as building blocks for wood and other plant structures. Every part of the plant requires sugars, but most photosynthesis happens in the leaves and stems, so the sugars need to be able to move around the plant to wherever they are needed. Phloem tubes form a network that transports sugar, proteins and other molecules around the plant within a fluid known as sap. Because this network is so extensive, it is very difficult to study, which has left researchers with major questions about how it works. For example, it is not clear how the sugar and other molecules leave the phloem when they reach their destination. Ross-Elliot et al. used a combination of microscopy and mathematical modeling to investigate how sugars and other molecules leave the phloem in the roots of a plant called Arabidopsis thaliana. The experiments show that these molecules move directly into cells within a neighboring tissue called the phloem-pole pericycle via pores known as funnel plasmodesmata. Ross-Elliot et al. incorporated the experimental data into a mathematical model of phloem unloading. This model suggests that sugars and other small molecules move freely through the funnel plasmodesmata, but large proteins pass through these pores in pulses. Future challenges include finding out exactly how plants control phloem unloading and to investigate whether it is possible to modify the delivery of specific molecules to particular parts of the plant. DOI:http://dx.doi.org/10.7554/eLife.24125.002
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Affiliation(s)
| | - Kaare H Jensen
- Department of Physics, Technical University of Denmark, Lyngby, Denmark
| | - Katrine S Haaning
- Department of Physics, Technical University of Denmark, Lyngby, Denmark
| | - Brittney M Wager
- School of Biological Sciences, Washington State University, Pullman, United States
| | - Jan Knoblauch
- School of Biological Sciences, Washington State University, Pullman, United States
| | - Alexander H Howell
- School of Biological Sciences, Washington State University, Pullman, United States
| | - Daniel L Mullendore
- School of Biological Sciences, Washington State University, Pullman, United States
| | - Alexander G Monteith
- Department of Biological and Medical Sciences, Oxford Brookes University, Headington, Oxford, United Kingdom
| | - Danae Paultre
- Institute of Molecular Plant Science, University of Edinburgh, Edinburgh, United Kingdom
| | - Dawei Yan
- Sainsbury Laboratory, University of Cambridge, Cambridge, United Kingdom
| | - Sofia Otero
- Sainsbury Laboratory, University of Cambridge, Cambridge, United Kingdom
| | - Matthieu Bourdon
- Sainsbury Laboratory, University of Cambridge, Cambridge, United Kingdom
| | - Ross Sager
- Department of Plant and Soil Sciences, Delaware Biotechnology Institute, University of Delaware, Newark, United States
| | - Jung-Youn Lee
- Department of Plant and Soil Sciences, Delaware Biotechnology Institute, University of Delaware, Newark, United States
| | - Ykä Helariutta
- Sainsbury Laboratory, University of Cambridge, Cambridge, United Kingdom
| | - Michael Knoblauch
- School of Biological Sciences, Washington State University, Pullman, United States
| | - Karl J Oparka
- Institute of Molecular Plant Science, University of Edinburgh, Edinburgh, United Kingdom
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36
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Pallas B, Da Silva D, Valsesia P, Yang W, Guillaume O, Lauri PE, Vercambre G, Génard M, Costes E. Simulation of carbon allocation and organ growth variability in apple tree by connecting architectural and source-sink models. ANNALS OF BOTANY 2016; 118:317-30. [PMID: 27279576 PMCID: PMC4970356 DOI: 10.1093/aob/mcw085] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2016] [Revised: 02/29/2016] [Accepted: 03/28/2016] [Indexed: 05/13/2023]
Abstract
BACKGROUND AND AIMS Plant growth depends on carbon availability and allocation among organs. QualiTree has been designed to simulate carbon allocation and partitioning in the peach tree (Prunus persica), whereas MappleT is dedicated to the simulation of apple tree (Malus × domestica) architecture. The objective of this study was to couple both models and adapt QualiTree to apple trees to simulate organ growth traits and their within-tree variability. METHODS MappleT was used to generate architectures corresponding to the 'Fuji' cultivar, accounting for the variability within and among individuals. These architectures were input into QualiTree to simulate shoot and fruit growth during a growth cycle. We modified QualiTree to account for the observed shoot polymorphism in apple trees, i.e. different classes (long, medium and short) that were characterized by different growth function parameters. Model outputs were compared with observed 3D tree geometries, considering shoot and final fruit size and growth dynamics. KEY RESULTS The modelling approach connecting MappleT and QualiTree was appropriate to the simulation of growth and architectural characteristics at the tree scale (plant leaf area, shoot number and types, fruit weight at harvest). At the shoot scale, mean fruit weight and its variability within trees was accurately simulated, whereas the model tended to overestimate individual shoot leaf area and underestimate its variability for each shoot type. Varying the parameter related to the intensity of carbon exchange between shoots revealed that behaviour intermediate between shoot autonomy and a common assimilate pool was required to properly simulate within-tree fruit growth variability. Moreover, the model correctly dealt with the crop load effect on organ growth. CONCLUSIONS This study provides understanding of the integration of shoot ontogenetic properties, carbon supply and transport between entities for simulating organ growth in trees. Further improvements regarding the integration of retroaction loops between carbon allocation and the resulting plant architecture are expected to allow multi-year simulations.
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Affiliation(s)
- Benoît Pallas
- Institut National de la Recherche Agronomique (INRA), UMR 1334 AGAP, CIRAD-INRA-Montpellier SupAgro, F-34398 Montpellier, France,
| | - David Da Silva
- Institut National de la Recherche Agronomique (INRA), UMR 1334 AGAP, CIRAD-INRA-Montpellier SupAgro, F-34398 Montpellier, France
| | - Pierre Valsesia
- INRA, UR 1115 Plantes et Systèmes de Culture Horticoles, F-84914 Avignon, France and
| | - Weiwei Yang
- College of Horticulture, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - Olivier Guillaume
- Institut National de la Recherche Agronomique (INRA), UMR 1334 AGAP, CIRAD-INRA-Montpellier SupAgro, F-34398 Montpellier, France
| | - Pierre-Eric Lauri
- Institut National de la Recherche Agronomique (INRA), UMR 1334 AGAP, CIRAD-INRA-Montpellier SupAgro, F-34398 Montpellier, France
| | - Gilles Vercambre
- INRA, UR 1115 Plantes et Systèmes de Culture Horticoles, F-84914 Avignon, France and
| | - Michel Génard
- INRA, UR 1115 Plantes et Systèmes de Culture Horticoles, F-84914 Avignon, France and
| | - Evelyne Costes
- Institut National de la Recherche Agronomique (INRA), UMR 1334 AGAP, CIRAD-INRA-Montpellier SupAgro, F-34398 Montpellier, France
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37
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Knoblauch J, Tepler Drobnitch S, Peters WS, Knoblauch M. In situ microscopy reveals reversible cell wall swelling in kelp sieve tubes: one mechanism for turgor generation and flow control? PLANT, CELL & ENVIRONMENT 2016; 39:1727-36. [PMID: 26991892 DOI: 10.1111/pce.12736] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2015] [Revised: 03/01/2016] [Accepted: 03/03/2016] [Indexed: 06/05/2023]
Abstract
Kelps, brown algae (Phaeophyceae) of the order Laminariales, possess sieve tubes for the symplasmic long-distance transport of photoassimilates that are evolutionarily unrelated but structurally similar to the tubes in the phloem of vascular plants. We visualized sieve tube structure and wound responses in fully functional, intact Bull Kelp (Nereocystis luetkeana [K. Mertens] Postels & Ruprecht 1840). In injured tubes, apparent slime plugs formed but were unlikely to cause sieve tube occlusion as they assembled at the downstream side of sieve plates. Cell walls expanded massively in the radial direction, reducing the volume of the wounded sieve elements by up to 90%. Ultrastructural examination showed that a layer of the immediate cell wall characterized by circumferential cellulose fibrils was responsible for swelling and suggested that alginates, abundant gelatinous polymers of the cell wall matrix, were involved. Wall swelling was rapid, reversible and depended on intracellular pressure, as demonstrated by pressure-injection of silicon oil. Our results revive the concept of turgor generation and buffering by swelling cell walls, which had fallen into oblivion over the last century. Because sieve tube transport is pressure-driven and controlled physically by tube diameter, a regulatory role of wall swelling in photoassimilate distribution is implied in kelps.
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Affiliation(s)
- Jan Knoblauch
- School of Biological Sciences, Washington State University, Pullman, WA, 99164, USA
| | - Sarah Tepler Drobnitch
- Department of Ecology and Evolutionary Biology, University of California Santa Cruz, Santa Cruz, CA, 95060, USA
| | - Winfried S Peters
- School of Biological Sciences, Washington State University, Pullman, WA, 99164, USA
| | - Michael Knoblauch
- School of Biological Sciences, Washington State University, Pullman, WA, 99164, USA
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38
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Hammes UZ. Under pressure. eLife 2016; 5. [PMID: 27417294 PMCID: PMC4946877 DOI: 10.7554/elife.18435] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2016] [Accepted: 07/08/2016] [Indexed: 12/02/2022] Open
Abstract
The movement of water by osmosis causes pressure differences that drive the transport of sugars over long distances in plants.
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Affiliation(s)
- Ulrich Z Hammes
- Department of Cell Biology and Plant Biochemistry, Regensburg University, Regensburg, Germany
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39
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Knoblauch M, Knoblauch J, Mullendore DL, Savage JA, Babst BA, Beecher SD, Dodgen AC, Jensen KH, Holbrook NM. Testing the Münch hypothesis of long distance phloem transport in plants. eLife 2016; 5:e15341. [PMID: 27253062 PMCID: PMC4946904 DOI: 10.7554/elife.15341] [Citation(s) in RCA: 99] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2016] [Accepted: 06/01/2016] [Indexed: 02/03/2023] Open
Abstract
Long distance transport in plants occurs in sieve tubes of the phloem. The pressure flow hypothesis introduced by Ernst Münch in 1930 describes a mechanism of osmotically generated pressure differentials that are supposed to drive the movement of sugars and other solutes in the phloem, but this hypothesis has long faced major challenges. The key issue is whether the conductance of sieve tubes, including sieve plate pores, is sufficient to allow pressure flow. We show that with increasing distance between source and sink, sieve tube conductivity and turgor increases dramatically in Ipomoea nil. Our results provide strong support for the Münch hypothesis, while providing new tools for the investigation of one of the least understood plant tissues.
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Affiliation(s)
- Michael Knoblauch
- School of Biological Sciences, Washington State University, Pullman, United States
| | - Jan Knoblauch
- School of Biological Sciences, Washington State University, Pullman, United States
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, United States
| | - Daniel L Mullendore
- School of Biological Sciences, Washington State University, Pullman, United States
| | - Jessica A Savage
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, United States
- Arnold Arboretum of Harvard University, Boston, United States
| | - Benjamin A Babst
- Department of Biosciences, Brookhaven National Laboratory, Upton, New York
| | - Sierra D Beecher
- School of Biological Sciences, Washington State University, Pullman, United States
| | - Adam C Dodgen
- School of Biological Sciences, Washington State University, Pullman, United States
| | - Kaare H Jensen
- Department of Physics, Technical University of Denmark, Lyngby, Denmark
| | - N Michele Holbrook
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, United States
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Knoblauch J, Peters WS, Knoblauch M. The gelatinous extracellular matrix facilitates transport studies in kelp: visualization of pressure-induced flow reversal across sieve plates. ANNALS OF BOTANY 2016; 117:599-606. [PMID: 26929203 PMCID: PMC4817499 DOI: 10.1093/aob/mcw007] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2015] [Revised: 11/07/2015] [Accepted: 12/08/2015] [Indexed: 06/05/2023]
Abstract
BACKGROUND AND AIMS In vascular plants, important questions regarding phloem function remain unanswered due to problems with invasive experimental procedures in this highly sensitive tissue. Certain brown algae (kelps; Laminariales) also possess sieve tubes for photoassimilate transport, but these are embedded in large volumes of a gelatinous extracellular matrix which isolates them from neighbouring cells. Therefore, we hypothesized that kelp sieve tubes might tolerate invasive experimentation better than their analogues in higher plants, and sought to establish Nereocystis luetkeana as an experimental system. METHODS The predominant localization of cellulose and the gelatinous extracellular matrix in N. luetkeana was verified using specific fluorescent markers and confocal laser scanning microscopy. Sieve tubes in intact specimens were loaded with fluorescent dyes, either passively (carboxyfluorescein diacetate; CFDA) or by microinjection (rhodamine B), and the movement of the dyes was monitored by fluorescence microscopy. KEY RESULTS Application of CFDA demonstrated source to sink bulk flow in N. luetkeana sieve tubes, and revealed the complexity of sieve tube structure, with branches, junctions and lateral connections. Microinjection into sieve elements proved comparatively easy. Pulsed rhodamine B injection enabled the determination of flow velocity in individual sieve elements, and the direct visualization of pressure-induced reversals of flow direction across sieve plates. CONCLUSIONS The reversal of flow direction across sieve plates by pressurizing the downstream sieve element conclusively demonstrates that a critical requirement of the Münch theory is satisfied in kelp; no such evidence exists for tracheophytes. Because of the high tolerance of its sieve elements to experimental manipulation, N. luetkeana is a promising alternative to vascular plants for studying the fluid mechanics of sieve tube networks.
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Affiliation(s)
- Jan Knoblauch
- School of Biological Sciences, Washington State University, PO Box 644236, Pullman, WA 99164, USA
| | - Winfried S Peters
- School of Biological Sciences, Washington State University, PO Box 644236, Pullman, WA 99164, USA
| | - Michael Knoblauch
- School of Biological Sciences, Washington State University, PO Box 644236, Pullman, WA 99164, USA
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Bandopadhyay A, Mandal S, Chakraborty S. Streaming potential-modulated capillary filling dynamics of immiscible fluids. SOFT MATTER 2016; 12:2056-2065. [PMID: 26758228 DOI: 10.1039/c5sm02687c] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The pressure driven transport of two immiscible electrolytes in a narrow channel with prescribed surface potential (zeta potential) is considered under the influence of a flow-induced electric field. The latter consideration is non-trivially and fundamentally different from the problem of electric field-driven motion (electroosmosis) of two immiscible electrolytes in a channel in a sense that in the former case, the genesis of the induced electric field, termed as streaming potential, is the advection of ions in the absence of any external electric field. As the flow occurs, one fluid displaces the other. Consequently, in cases where the conductivities of the two fluids differ, imbibition dynamically alters the net conductivity of the channel. We emphasize, through numerical simulations, that the alteration in the net conductivity has a significant impact on the contact line dynamics and the concomitant induced streaming potential. The results presented herein are expected to shed light on multiphase electrokinetics devices.
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Affiliation(s)
- Aditya Bandopadhyay
- Advanced Technology Development Center, Indian Institute of Technology Kharagpur, Kharagpur - 721302, India
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42
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Epron D, Cabral OMR, Laclau JP, Dannoura M, Packer AP, Plain C, Battie-Laclau P, Moreira MZ, Trivelin PCO, Bouillet JP, Gérant D, Nouvellon Y. In situ 13CO2 pulse labelling of field-grown eucalypt trees revealed the effects of potassium nutrition and throughfall exclusion on phloem transport of photosynthetic carbon. TREE PHYSIOLOGY 2016; 36:6-21. [PMID: 26423335 DOI: 10.1093/treephys/tpv090] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2015] [Accepted: 08/10/2015] [Indexed: 05/15/2023]
Abstract
Potassium (K) is an important limiting factor of tree growth, but little is known of the effects of K supply on the long-distance transport of photosynthetic carbon (C) in the phloem and of the interaction between K fertilization and drought. We pulse-labelled 2-year-old Eucalyptus grandis L. trees grown in a field trial combining K fertilization (+K and -K) and throughfall exclusion (+W and -W), and we estimated the velocity of C transfer by comparing time lags between the uptake of (13)CO2 and its recovery in trunk CO2 efflux recorded at different heights. We also analysed the dynamics of the labelled photosynthates recovered in the foliage and in the phloem sap (inner bark extract). The mean residence time of labelled C in the foliage was short (21-31 h). The time series of (13)C in excess in the foliage was affected by the level of fertilization, whereas the effect of throughfall exclusion was not significant. The velocity of C transfer in the trunk (0.20-0.82 m h(-1)) was twice as high in +K trees than in -K trees, with no significant effect of throughfall exclusion except for one +K -W tree labelled in the middle of the drought season that was exposed to a more pronounced water stress (midday leaf water potential of -2.2 MPa). Our results suggest that besides reductions in photosynthetic C supply and in C demand by sink organs, the lower velocity under K deficiency is due to a lower cross-sectional area of the sieve tubes, whereas an increase in phloem sap viscosity is more likely limiting phloem transport under drought. In all treatments, 10 times less (13)C was recovered in inner bark extracts at the bottom of the trunk when compared with the base of the crown, suggesting that a large part of the labelled assimilates has been exported out of the phloem and replaced by unlabelled C. This supports the 'leakage-retrieval mechanism' that may play a role in maintaining the pressure gradient between source and sink organs required to sustain high velocity of phloem transport in tall trees.
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Affiliation(s)
- Daniel Epron
- UMR 1137, Ecologie et Ecophysiologie Forestières, Faculté des Sciences, Université de Lorraine, F-54500 Vandoeuvre-les-Nancy, France INRA, UMR 1137, Ecologie et Ecophysiologie Forestières, Centre de Nancy, F-54280 Champenoux, France CIRAD, UMR Eco&sols, Ecologie Fonctionnelle & Biogéochimie des Sols & Agro-écosystèmes, F-34060 Montpellier, France
| | | | - Jean-Paul Laclau
- CIRAD, UMR Eco&sols, Ecologie Fonctionnelle & Biogéochimie des Sols & Agro-écosystèmes, F-34060 Montpellier, France Universidade Estadual de São Paulo, Botucatu, CEP 18610-300 São Paulo, Brazil Departamento de Ciências Florestais, ESALQ, Universidade de São Paulo, ESALQ, CEP 13418-900 Piracicaba, São Paulo, Brazil
| | - Masako Dannoura
- Laboratory of Forest Utilization, Department of Forest and Biomaterial Science, Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan
| | - Ana Paula Packer
- Embrapa Meio Ambiente, CEP 13820-000, Jaguariúna, São Paulo, Brazil
| | - Caroline Plain
- UMR 1137, Ecologie et Ecophysiologie Forestières, Faculté des Sciences, Université de Lorraine, F-54500 Vandoeuvre-les-Nancy, France INRA, UMR 1137, Ecologie et Ecophysiologie Forestières, Centre de Nancy, F-54280 Champenoux, France
| | - Patricia Battie-Laclau
- Centro de Energia Nuclear na Agricultura, Universidade de São Paulo, CEP 13400-970 Piracicaba, São Paulo, Brazil
| | - Marcelo Zacharias Moreira
- Centro de Energia Nuclear na Agricultura, Universidade de São Paulo, CEP 13400-970 Piracicaba, São Paulo, Brazil
| | - Paulo Cesar Ocheuze Trivelin
- Centro de Energia Nuclear na Agricultura, Universidade de São Paulo, CEP 13400-970 Piracicaba, São Paulo, Brazil
| | - Jean-Pierre Bouillet
- CIRAD, UMR Eco&sols, Ecologie Fonctionnelle & Biogéochimie des Sols & Agro-écosystèmes, F-34060 Montpellier, France Departamento de Ciências Florestais, ESALQ, Universidade de São Paulo, ESALQ, CEP 13418-900 Piracicaba, São Paulo, Brazil
| | - Dominique Gérant
- UMR 1137, Ecologie et Ecophysiologie Forestières, Faculté des Sciences, Université de Lorraine, F-54500 Vandoeuvre-les-Nancy, France INRA, UMR 1137, Ecologie et Ecophysiologie Forestières, Centre de Nancy, F-54280 Champenoux, France
| | - Yann Nouvellon
- CIRAD, UMR Eco&sols, Ecologie Fonctionnelle & Biogéochimie des Sols & Agro-écosystèmes, F-34060 Montpellier, France Departamento de Ciências Atmosféricas, IAG, Universidade de São Paulo, ESALQ, CEP 05508-900 São Paulo, Brazil
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Liesche J. How regulation of phloem transport could link potassium fertilization to increased growth. TREE PHYSIOLOGY 2016; 36:1-5. [PMID: 26612849 DOI: 10.1093/treephys/tpv120] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2015] [Accepted: 10/13/2015] [Indexed: 06/05/2023]
Affiliation(s)
- Johannes Liesche
- College of Life Sciences, Northwest A&F University, Yangling, Shaanxi 712100, China
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Savage JA, Haines DF, Holbrook NM. The making of giant pumpkins: how selective breeding changed the phloem of Cucurbita maxima from source to sink. PLANT, CELL & ENVIRONMENT 2015; 38:1543-1554. [PMID: 25546629 DOI: 10.1111/pce.12502] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2014] [Revised: 12/16/2014] [Accepted: 12/17/2014] [Indexed: 06/04/2023]
Abstract
Despite the success of breeding programmes focused on increasing fruit size, relatively little is known about the anatomical and physiological changes required to increase reproductive allocation. To address this gap in knowledge, we compared fruit/ovary anatomy, vascular structure and phloem transport of two varieties of giant pumpkins, and their smaller fruited progenitor under controlled environmental conditions. We also modelled carbon transport into the fruit of competitively grown plants using data collected in the field. There was no evidence that changes in leaf area or photosynthetic capacity impacted fruit size. Instead, giant varieties differed in their ovary morphology and contained more phloem on a cross-sectional area basis in their petioles and pedicels than the ancestral variety. These results suggest that sink activity is important in determining fruit size and that giant pumpkins have an enhanced capacity to transport carbon. The strong connection observed between carbon fixation, phloem structure and fruit growth in field-grown plants indicates that breeding for large fruit has led to changes throughout the carbon transport system that could have important implications for how we think about phloem transport velocity and carbon allocation.
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Affiliation(s)
- Jessica A Savage
- Arnold Arboretum, Harvard University, Boston, MA, 02131, USA
- Department of Organismic and Evolutionary Biology, Harvard University, Boston, MA, 02131, USA
| | - Dustin F Haines
- Department of Organismic and Evolutionary Biology, Harvard University, Boston, MA, 02131, USA
| | - N Michele Holbrook
- Department of Organismic and Evolutionary Biology, Harvard University, Boston, MA, 02131, USA
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45
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Liesche J, Windt C, Bohr T, Schulz A, Jensen KH. Slower phloem transport in gymnosperm trees can be attributed to higher sieve element resistance. TREE PHYSIOLOGY 2015; 35:376-86. [PMID: 25787331 DOI: 10.1093/treephys/tpv020] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2014] [Accepted: 02/10/2015] [Indexed: 05/09/2023]
Abstract
In trees, carbohydrates produced in photosynthesizing leaves are transported to roots and other sink organs over distances of up to 100 m inside a specialized transport tissue, the phloem. Angiosperm and gymnosperm trees have a fundamentally different phloem anatomy with respect to cell size, shape and connectivity. Whether these differences have an effect on the physiology of carbohydrate transport, however, is not clear. A meta-analysis of the experimental data on phloem transport speed in trees yielded average speeds of 56 cm h(-1) for angiosperm trees and 22 cm h(-1) for gymnosperm trees. Similar values resulted from theoretical modeling using a simple transport resistance model. Analysis of the model parameters clearly identified sieve element (SE) anatomy as the main factor for the significantly slower carbohydrate transport speed inside the phloem in gymnosperm compared with angiosperm trees. In order to investigate the influence of SE anatomy on the hydraulic resistance, anatomical data on SEs and sieve pores were collected by transmission electron microscopy analysis and from the literature for 18 tree species. Calculations showed that the hydraulic resistance is significantly higher in the gymnosperm than in angiosperm trees. The higher resistance is only partially offset by the considerably longer SEs of gymnosperms.
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Affiliation(s)
- Johannes Liesche
- Department of Plant and Environmental Sciences, University of Copenhagen, 1871 Frederiksberg, Denmark
| | - Carel Windt
- Forschungszentrum Jülich, IBG-2: Plant Sciences, 52428 Jülich, Germany
| | - Tomas Bohr
- Department of Physics, Technical University of Denmark, 2800 Kgs Lyngby, Denmark
| | - Alexander Schulz
- Department of Plant and Environmental Sciences, University of Copenhagen, 1871 Frederiksberg, Denmark
| | - Kaare H Jensen
- Department of Physics, Technical University of Denmark, 2800 Kgs Lyngby, Denmark
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Eves-van den Akker S, Lilley C, Jones J, Urwin P. Plant-parasitic nematode feeding tubes and plugs: new perspectives on function. NEMATOLOGY 2015. [DOI: 10.1163/15685411-00002832] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Several structures associated with feeding by plant-parasitic nematodes have been described using two terms, feeding tubes and feeding plugs. However, both of these terms encompass multiple structures of independent evolution, some of which are functionally distinct. We have reviewed the literature on both structures and provide a new perspective on the function of intracellular feeding tubes to maintain the integrity and efficacy of the feeding site. We propose that they provide sufficient hydraulic resistance against the feeding site pressure to prevent it from collapsing during feeding. In addition, we propose that extracellular feeding tubes of migratory ectoparasites should be considered as the functional analogue of the stylet of all other plant-parasitic nematodes for withdrawal of host cell cytoplasm and, therefore, provide an example of convergent evolution. We also suggest that the main role of the feeding plug, irrespective of origin or composition, may be in adhesion.
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Affiliation(s)
- Sebastian Eves-van den Akker
- Centre for Plant Sciences, University of Leeds, Leeds, LS2 9JT, UK
- Cell and Molecular Sciences Group, Dundee Effector Consortium, James Hutton Institute, Invergowrie, Dundee, DD2 5DA, UK
| | | | - John T. Jones
- Cell and Molecular Sciences Group, Dundee Effector Consortium, James Hutton Institute, Invergowrie, Dundee, DD2 5DA, UK
| | - Peter E. Urwin
- Centre for Plant Sciences, University of Leeds, Leeds, LS2 9JT, UK
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Hammel JU, Nickel M. A new flow-regulating cell type in the Demosponge Tethya wilhelma - functional cellular anatomy of a leuconoid canal system. PLoS One 2014; 9:e113153. [PMID: 25409176 PMCID: PMC4237394 DOI: 10.1371/journal.pone.0113153] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2014] [Accepted: 10/20/2014] [Indexed: 12/25/2022] Open
Abstract
Demosponges possess a leucon-type canal system which is characterized by a highly complex network of canal segments and choanocyte chambers. As sponges are sessile filter feeders, their aquiferous system plays an essential role in various fundamental physiological processes. Due to the morphological and architectural complexity of the canal system and the strong interdependence between flow conditions and anatomy, our understanding of fluid dynamics throughout leuconoid systems is patchy. This paper provides comprehensive morphometric data on the general architecture of the canal system, flow measurements and detailed cellular anatomical information to help fill in the gaps. We focus on the functional cellular anatomy of the aquiferous system and discuss all relevant cell types in the context of hydrodynamic and evolutionary constraints. Our analysis is based on the canal system of the tropical demosponge Tethya wilhelma, which we studied using scanning electron microscopy. We found a hitherto undescribed cell type, the reticuloapopylocyte, which is involved in flow regulation in the choanocyte chambers. It has a highly fenestrated, grid-like morphology and covers the apopylar opening. The minute opening of the reticuloapopylocyte occurs in an opened, intermediate and closed state. These states permit a gradual regulation of the total apopylar opening area. In this paper the three states are included in a theoretical study into flow conditions which aims to draw a link between functional cellular anatomy, the hydrodynamic situation and the regular body contractions seen in T. wilhelma. This provides a basis for new hypotheses regarding the function of bypass elements and the role of hydrostatic pressure in body contractions. Our study provides insights into the local and global flow conditions in the sponge canal system and thus enhances current understanding of related physiological processes.
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Affiliation(s)
- Jörg U. Hammel
- Institut für Spezielle Zoologie und Evolutionsbiologie mit Phyletischem Museum, Friedrich-Schiller-Universität Jena, Erbertstr. 1, 07743, Jena, Germany
| | - Michael Nickel
- Institut für Spezielle Zoologie und Evolutionsbiologie mit Phyletischem Museum, Friedrich-Schiller-Universität Jena, Erbertstr. 1, 07743, Jena, Germany
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Wulff NA, Zhang S, Setubal JC, Almeida NF, Martins EC, Harakava R, Kumar D, Rangel LT, Foissac X, Bové JM, Gabriel DW. The complete genome sequence of 'Candidatus Liberibacter americanus', associated with Citrus huanglongbing. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2014; 27:163-76. [PMID: 24200077 DOI: 10.1094/mpmi-09-13-0292-r] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Liberibacter spp. form a Rhizobiaceae clade of phloem-limited pathogens of limited host range. Two obligately parasitic species have been sequenced: 'Candidatus Liberibacter asiaticus', which causes citrus huanglongbing (HLB) worldwide, and 'Ca. L. solanacearum', which causes potato "zebra chip" disease. A third (proposed) species, Liberibacter crescens, was isolated from mountain papaya, grown in axenic culture, and sequenced. In an effort to identify common host determinants, the complete genomic DNA sequence of a second HLB species, 'Ca. L. americanus' strain 'São Paulo' was determined. The circular genome of 1,195,201 bp had an average 31.12% GC content and 983 predicted protein encoding genes, 800 (81.4%) of which had a predicted function. There were 658 genes common to all sequenced Liberibacter spp. and only 8 genes common to 'Ca. L. americanus' and 'Ca. L. asiaticus' but not found in 'Ca. L. solanacearum'. Surprisingly, most of the lipopolysaccharide biosynthetic genes were missing from the 'Ca. L. americanus' genome, as well as OmpA and a key regulator of flagellin, all indicating a 'Ca. L. americanus' strategy of avoiding production of major pathogen-associated molecular patterns present in 'Ca. L. asiaticus' and 'Ca. L. solanacearum'. As with 'Ca. L. asiaticus', one of two 'Ca. L. americanus' prophages replicated as an excision plasmid and carried potential lysogenic conversion genes that appeared fragmentary or degenerated in 'Ca. L. solanacearum'.
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Fanwoua J, Bairam E, Delaire M, Buck-Sorlin G. The role of branch architecture in assimilate production and partitioning: the example of apple (Malus domestica). FRONTIERS IN PLANT SCIENCE 2014; 5:338. [PMID: 25071813 PMCID: PMC4089354 DOI: 10.3389/fpls.2014.00338] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2014] [Accepted: 06/25/2014] [Indexed: 05/21/2023]
Abstract
Understanding the role of branch architecture in carbon production and allocation is essential to gain more insight into the complex process of assimilate partitioning in fruit trees. This mini review reports on the current knowledge of the role of branch architecture in carbohydrate production and partitioning in apple. The first-order carrier branch of apple illustrates the complexity of branch structure emerging from bud activity events and encountered in many fruit trees. Branch architecture influences carbon production by determining leaf exposure to light and by affecting leaf internal characteristics related to leaf photosynthetic capacity. The dynamics of assimilate partitioning between branch organs depends on the stage of development of sources and sinks. The sink strength of various branch organs and their relative positioning on the branch also affect partitioning. Vascular connections between branch organs determine major pathways for branch assimilate transport. We propose directions for employing a modeling approach to further elucidate the role of branch architecture on assimilate partitioning.
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Affiliation(s)
- Julienne Fanwoua
- *Correspondence: Julienne Fanwoua, UMR 1345 Institut de Recherche en Horticulture et Semences, AGROCAMPUS OUEST-Centre d’Angers, Institut National d’Horticulture et de Paysage 2 Rue André le Notre, 49045 Angers Cedex 01, France e-mail:
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Knoblauch M, Peters WS. Long-distance translocation of photosynthates: a primer. PHOTOSYNTHESIS RESEARCH 2013; 117:189-196. [PMID: 23754670 DOI: 10.1007/s11120-013-9867-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2013] [Accepted: 05/29/2013] [Indexed: 06/02/2023]
Abstract
The storage of light energy in chemical form through photosynthesis is the key process underlying life as we know it. To utilize photosynthates efficiently as structural materials or as fuel to drive endergonic processes, they have to be transported from where they are produced to where they are needed. In this primer, we provide an overview of basic biophysical concepts underlying our current understanding of the mechanisms of photosynthate long-distance transport, and briefly discuss current developments in the field.
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Affiliation(s)
- Michael Knoblauch
- School of Biological Sciences, Washington State University, PO Box 644236, Pullman, WA, 99164-4236, USA,
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