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Baird AS, Taylor SH, Reddi S, Pasquet-Kok J, Vuong C, Zhang Y, Watcharamongkol T, John GP, Scoffoni C, Osborne CP, Sack L. Allometries of cell and tissue anatomy and photosynthetic rate across leaves of C 3 and C 4 grasses. PLANT, CELL & ENVIRONMENT 2024; 47:156-173. [PMID: 37876323 DOI: 10.1111/pce.14741] [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: 02/25/2023] [Revised: 06/26/2023] [Accepted: 10/09/2023] [Indexed: 10/26/2023]
Abstract
Allometric relationships among the dimensions of leaves and their cells hold across diverse eudicotyledons, but have remained untested in the leaves of grasses. We hypothesised that geometric (proportional) allometries of cell sizes across tissues and of leaf dimensions would arise due to the coordination of cell development and that of cell functions such as water, nutrient and energy transport, and that cell sizes across tissues would be associated with light-saturated photosynthetic rate. We tested predictions across 27 globally distributed C3 and C4 grass species grown in a common garden. We found positive relationships among average cell sizes within and across tissues, and of cell sizes with leaf dimensions. Grass leaf anatomical allometries were similar to those of eudicots, with exceptions consistent with the fewer cell layers and narrower form of grass leaves, and the specialised roles of epidermis and bundle sheath in storage and leaf movement. Across species, mean cell sizes in each tissue were associated with light-saturated photosynthetic rate per leaf mass, supporting the functional coordination of cell sizes. These findings highlight the generality of evolutionary allometries within the grass lineage and their interlinkage with coordinated development and function.
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Affiliation(s)
- Alec S Baird
- Department of Ecology and Evolutionary Biology, University of California Los Angeles, Los Angeles, California, USA
| | - Samuel H Taylor
- Lancaster Environment Centre, Lancaster University, Lancaster, UK
| | - Sachin Reddi
- Department of Ecology and Evolutionary Biology, University of California Los Angeles, Los Angeles, California, USA
| | - Jessica Pasquet-Kok
- Department of Ecology and Evolutionary Biology, University of California Los Angeles, Los Angeles, California, USA
| | - Christine Vuong
- Department of Ecology and Evolutionary Biology, University of California Los Angeles, Los Angeles, California, USA
| | - Yu Zhang
- Department of Ecology and Evolutionary Biology, University of California Los Angeles, Los Angeles, California, USA
| | - Teera Watcharamongkol
- Department of Animal and Plant Sciences, University of Sheffield, Sheffield, UK
- Faculty of Science and Technology, Kanchanaburi Rajabhat University, Kanchanaburi, Thailand
| | - Grace P John
- Department of Ecology and Evolutionary Biology, University of California Los Angeles, Los Angeles, California, USA
- Department of Biology, University of Florida, Gainesville, Florida, USA
| | - Christine Scoffoni
- Department of Ecology and Evolutionary Biology, University of California Los Angeles, Los Angeles, California, USA
- Department of Biological Sciences, California State University Los Angeles, Los Angeles, California, USA
| | - Colin P Osborne
- Department of Animal and Plant Sciences, University of Sheffield, Sheffield, UK
| | - Lawren Sack
- Department of Ecology and Evolutionary Biology, University of California Los Angeles, Los Angeles, California, USA
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2
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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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3
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Fiorella RP, Kannenberg SA, Anderegg WRL, Monson RK, Ehleringer JR. Heterogeneous isotope effects decouple conifer leaf and branch sugar δ 18O and δ 13C. Oecologia 2022; 198:357-370. [PMID: 35107645 DOI: 10.1007/s00442-022-05121-y] [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] [Received: 04/19/2021] [Accepted: 01/21/2022] [Indexed: 10/19/2022]
Abstract
Isotope ratios of tree-ring cellulose are a prominent tool to reconstruct paleoclimate and plant responses to environmental variation. Current models for cellulose isotope ratios assume a transfer of the environmental signals recorded in bulk leaf water to carbohydrates and ultimately into stem cellulose. However, the isotopic signal of carbohydrates exported from leaf to branch may deviate from mean leaf values if spatial heterogeneity in isotope ratios exists in the leaf. We tested whether the isotopic heterogeneity previously observed along the length of a ponderosa pine (Pinus ponderosa) leaf water was preserved in photosynthetic products. We observed an increase in both sugar and bulk tissue δ18O values along the needle, but the increase in carbohydrate δ18O values was dampened relative to the trend observed in leaf water. In contrast, δ13C values of both sugar and bulk organic matter were invariant along the needle. Phloem-exported sugar measured in the branch below the needles did not match whole-needle values of δ18O or δ13C. Instead, there was a near-constant offset observed between the branch and needle sugar δ13C values, while branch δ18O values were most similar to δ18O values observed for sugar at the base of the needle. The observed offset between the branch and needle sugar δ18O values likely arises from partial isotope oxygen exchange between sugars and water during phloem loading and transport. An improved understanding of the conditions producing differential δ13C and δ18O isotope effects between branch phloem and needle sugars could improve tree-ring-based climate reconstructions.
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Affiliation(s)
- Richard P Fiorella
- Department of Geology and Geophysics, University of Utah, Salt Lake City, UT, 84112, USA.
- Global Change and Sustainability Center, University of Utah, Salt Lake City, UT, 84112, USA.
- Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA.
| | - Steven A Kannenberg
- School of Biological Sciences, University of Utah, Salt Lake City, UT, 84112, USA
| | - William R L Anderegg
- Global Change and Sustainability Center, University of Utah, Salt Lake City, UT, 84112, USA
- School of Biological Sciences, University of Utah, Salt Lake City, UT, 84112, USA
| | - Russell K Monson
- Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ, 85721, USA
- Laboratory of Tree Ring Research, University of Arizona, Tucson, AZ, 85721, USA
| | - James R Ehleringer
- Global Change and Sustainability Center, University of Utah, Salt Lake City, UT, 84112, USA
- School of Biological Sciences, University of Utah, Salt Lake City, UT, 84112, USA
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4
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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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Jung Y, Park K, Jensen KH, Kim W, Kim HY. A design principle of root length distribution of plants. J R Soc Interface 2019; 16:20190556. [PMID: 31795862 DOI: 10.1098/rsif.2019.0556] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Shaping a plant root into an ideal structure for water capture is increasingly important for sustainable agriculture in the era of global climate change. Although the current genetic engineering of crops favours deep-reaching roots, here we show that nature has apparently adopted a different strategy of shaping roots. We construct a mathematical model for optimal root length distribution by considering that plants seek maximal water uptake at the metabolic expenses of root growth. Our theory finds a logarithmic decrease of root length density with depth to be most beneficial for efficient water uptake, which is supported by biological data as well as our experiments using root-mimicking network systems. Our study provides a tool to gauge the relative performance of root networks in transgenic plants engineered to endure a water deficit. Moreover, we lay a fundamental framework for mechanical understanding and design of water-absorptive growing networks, such as medical and industrial fluid transport systems and soft robots, which grow in porous media including soils and biotissues.
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Affiliation(s)
- Yeonsu Jung
- Department of Mechanical and Aerospace Engineering, Seoul National University, Seoul 08826, Korea
| | - Keunhwan Park
- Department of Physics, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
| | - Kaare H Jensen
- Department of Physics, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
| | - Wonjung Kim
- Department of Mechanical Engineering, Sogang University, Seoul 04107, Korea
| | - Ho-Young Kim
- Department of Mechanical and Aerospace Engineering, Seoul National University, Seoul 08826, Korea
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6
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Jankowski A, Wyka TP, Żytkowiak R, Danusevičius D, Oleksyn J. Does climate-related in situ variability of Scots pine (Pinus sylvestris L.) needles have a genetic basis? Evidence from common garden experiments. TREE PHYSIOLOGY 2019; 39:573-589. [PMID: 30715504 DOI: 10.1093/treephys/tpy145] [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: 06/19/2018] [Revised: 11/28/2018] [Accepted: 12/17/2018] [Indexed: 06/09/2023]
Abstract
The correlations of phenotypic traits with environmental drivers suggest that variability of these traits is a result of natural selection, especially if such trait correlations are based on genetic variability. We hypothesized that in situ correlations of structural needle traits of Scots pine (Pinus sylvestris L) with minimal winter temperature (Tmin) reported previously from a temperate/boreal transect would be conserved when plants are cultivated under common conditions. We tested this hypothesis by analyzing needles from two common gardens located in the temperate zone, one including adult trees and the other juvenile seedlings. The majority of adult needle traits for which correlations with Tmin were found in the field turned out to be under environmental influence. In contrast, the majority of traits studied in juvenile needles were correlated with the original Tmin suggesting the role of past natural selection in shaping their variability. Juvenile needles thus appeared to be inherently less plastic than adult needles, perhaps reflecting the stronger selective pressure acting during juvenile, as compared with adult, ontogenetic stage. Genetically based cold-climate adaptation in either juvenile or adult needles, or both, involved an increase in leaf mass per area and leaf density, decrease in needle length, reduction in the amount of xylem and phloem, increase in thickness of epidermis, decrease in tracheid diameter and increase in tracheid density, and increase in diameter and volume fraction of resin ducts. We also show that at least some traits, such as transverse xylem and phloem areas and number of fibers, scale with needle length, suggesting that climate-related trait variation may also be mediated by changes in needle length. Moreover, slopes of these allometric relationships may themselves be plastically modified. The phenotypic syndrome typical of needles from cold environments may thus be under environmental, genetic and allometric control.
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Affiliation(s)
- Artur Jankowski
- General Botany Laboratory, Adam Mickiewicz University, Faculty of Biology, Institute of Experimental Biology, Umultowska 89, Poznań, Poland
- Polish Academy of Sciences, Institute of Dendrology, Parkowa 5, Kórnik, Poland
| | - Tomasz P Wyka
- General Botany Laboratory, Adam Mickiewicz University, Faculty of Biology, Institute of Experimental Biology, Umultowska 89, Poznań, Poland
| | - Roma Żytkowiak
- Polish Academy of Sciences, Institute of Dendrology, Parkowa 5, Kórnik, Poland
| | - Darius Danusevičius
- Aleksandras Stulginskis University, Faculty of Forest Science and Ecology, Studentų str. 11, Akademija, Kaunas reg., Lithuania
| | - Jacek Oleksyn
- Polish Academy of Sciences, Institute of Dendrology, Parkowa 5, Kórnik, Poland
- Department of Forest Resources, University of Minnesota, St Paul, MN, USA
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7
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Han X, Turgeon R, Schulz A, Liesche J. Environmental conditions, not sugar export efficiency, limit the length of conifer leaves. TREE PHYSIOLOGY 2019; 39:312-319. [PMID: 29850887 DOI: 10.1093/treephys/tpy056] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2017] [Revised: 03/27/2018] [Accepted: 05/17/2018] [Indexed: 06/08/2023]
Abstract
Most conifer species have needle-shaped leaves that are only a few centimeters long. In general, variation in leaf size has been associated with environmental factors, such as cold or drought stress. However, it has recently been proposed that sugar export efficiency is the limiting factor for conifer needle length, based on the results obtained using a mathematical model of phloem transport. Here, phloem transport rates in long conifer needles were experimentally determined to test if the mathematical model accurately represents phloem transport. The validity of the model's assumptions was tested by anatomical analyses and sugar quantification. Furthermore, various environmental and physiological factors were tested for their correlation with needle length. The results indicate that needle length is not limited by sugar transport efficiency, but, instead, by winter temperatures and light availability. The identification of factors that influence needle size is instrumental for using this trait as a variable in breeding programs.
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Affiliation(s)
- Xiaoyu Han
- College of Life Science, Northwest A&F University, Nongling Road 10, Yangling, China
- Biomass Energy Center for Arid Lands, Northwest A&F University, Nongling Road 10, Yangling, China
| | - Robert Turgeon
- Plant Biology Section, School of Integrative Plant Science, Cornell University, 412 Mann Library Building, Ithaca, NY, USA
| | - Alexander Schulz
- Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, 1871 Frederiksberg C, Denmark
| | - Johannes Liesche
- College of Life Science, Northwest A&F University, Nongling Road 10, Yangling, China
- Biomass Energy Center for Arid Lands, Northwest A&F University, Nongling Road 10, Yangling, China
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8
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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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9
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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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10
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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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11
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Liesche J, Schulz A. Phloem transport in gymnosperms: a question of pressure and resistance. CURRENT OPINION IN PLANT BIOLOGY 2018; 43:36-42. [PMID: 29304388 DOI: 10.1016/j.pbi.2017.12.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2017] [Revised: 12/14/2017] [Accepted: 12/15/2017] [Indexed: 06/07/2023]
Abstract
Even in the highest trees, carbon is efficiently distributed from leaves to heterotrophic tissues like fruit, flowers and roots. This long-distance transport happens in the highly specialized sieve elements of the phloem. In gymnosperms, sieve element anatomy appears to be less suited for mass flow of phloem sap than that of angiosperms. This review covers available data on gymnosperm phloem to evaluate if it functions differently from that of angiosperms. Although current evidence suggests that, despite a higher pathway resistance, a single source-to-sink turgor pressure gradient can drive mass flow, several questions remain unanswered. These include how endoplasmic reticulum-complexes in sieve elements influence flow, as well as what the effect of symplasmic coupling along the whole phloem pathway could be.
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Affiliation(s)
- Johannes Liesche
- College of Life Science, Department of Biology, Northwest A&F University, 3 Taicheng Road, 712100 Yangling, Shaanxi, China
| | - Alexander Schulz
- Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark.
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12
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Carvalho MR, Losada JM, Niklas KJ. Phloem networks in leaves. CURRENT OPINION IN PLANT BIOLOGY 2018; 43:29-35. [PMID: 29306742 DOI: 10.1016/j.pbi.2017.12.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2017] [Revised: 12/04/2017] [Accepted: 12/16/2017] [Indexed: 06/07/2023]
Abstract
The survival of all vascular plants depends on phloem and xylem, which comprise a hydraulically coupled tissue system that transports photosynthates, water, and a variety of other molecules and ions. Although xylem hydraulics has been extensively studied, until recently, comparatively little is known quantitatively about the phloem hydraulic network and how it is functionally coupled to the xylem network, particularly in photosynthetic leaves. Here, we summarize recent advances in quantifying phloem hydraulics in fully expanded mature leaves with different vascular architectures and show that (1) the size of phloem conducting cells across phylogenetically different taxa scales isometrically with respect to xylem conducting cell size, (2) cell transport areas and lengths increase along phloem transport pathways in a manner that can be used to model Münch's pressure-flow hypothesis, and (3) report observations that invalidate da Vinci's and Murray's hydraulic models as plausible constructs for understanding photosynthate transport in the leaf lamina.
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Affiliation(s)
- Mónica R Carvalho
- Plant Biology Section, School of Integrative Plant Science, Cornell University, Ithaca, NY 14853, USA; Smithsonian Tropical Research Institute, Box 0843-03092, Balboa, Ancón, Panama
| | - Juan M Losada
- Arnold Arboretum, Harvard University, 1300 Centre St., Boston, MA 02131, USA
| | - Karl J Niklas
- Plant Biology Section, School of Integrative Plant Science, Cornell University, Ithaca, NY 14853, USA.
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13
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Carvalho MR, Turgeon R, Owens T, Niklas KJ. The hydraulic architecture of Ginkgo leaves. AMERICAN JOURNAL OF BOTANY 2017; 104:1285-1298. [PMID: 29885239 DOI: 10.3732/ajb.1700277] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Accepted: 08/31/2017] [Indexed: 05/24/2023]
Abstract
PREMISE OF THE STUDY The hydraulics of xylem has been widely studied in numerous species and organ types. However, comparatively little is known about how phloem and xylem are hydraulically coupled or about many of the basic structural properties of phloem (such as conducting cell numbers and conductive areas), which nevertheless have direct bearing on understanding phloem loading and unloading. METHODS Using a combination of light, epifluorescence, confocal, and transmission electron microscopy, we quantified the hydraulic architecture of Ginkgo biloba leaf laminae and examined the scaling relationships between phloem and xylem in five fully mature leaves. KEY RESULTS The conductive areas and lengths of sieve cells and tracheids increase basipetally toward the petiole in a manner that is consistent with Münch's pressure flow hypothesis for phloem transport. This trend holds true for individual veins, the sum of conductive areas across all veins at any distance from the petiole, and for individual sieve cells and tracheids. Further, the conductive areas of phloem and xylem are isometrically correlated across the entire vasculature of the leaf lamina. The data for conducting cell areas do not conform with the predictions of the hydraulic models of da Vinci and Murray. CONCLUSIONS The scaling of Ginkgo lamina hydraulics complies with that observed in leaves of other gymnosperms and most angiosperms and is inconsistent with theoretical models that assume that the volume of transported incompressible fluids is conserved.
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Affiliation(s)
- Mónica R Carvalho
- Plant Biology Section, School of Integrative Plant Science, Cornell University, Ithaca, New York 14853 USA
- Smithsonian Tropical Research Institute, Box 0843-03092, Balboa, Ancon Republic of Panama
| | - Robert Turgeon
- Plant Biology Section, School of Integrative Plant Science, Cornell University, Ithaca, New York 14853 USA
| | - Thomas Owens
- Plant Biology Section, School of Integrative Plant Science, Cornell University, Ithaca, New York 14853 USA
| | - Karl J Niklas
- Plant Biology Section, School of Integrative Plant Science, Cornell University, Ithaca, New York 14853 USA
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14
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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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15
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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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16
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Drobnitch ST, Jensen KH, Prentice P, Pittermann J. Convergent evolution of vascular optimization in kelp (Laminariales). Proc Biol Sci 2015; 282:20151667. [PMID: 26423844 PMCID: PMC4614777 DOI: 10.1098/rspb.2015.1667] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2015] [Accepted: 09/02/2015] [Indexed: 11/12/2022] Open
Abstract
Terrestrial plants and mammals, although separated by a great evolutionary distance, have each arrived at a highly conserved body plan in which universal allometric scaling relationships govern the anatomy of vascular networks and key functional metabolic traits. The universality of allometric scaling suggests that these phyla have each evolved an 'optimal' transport strategy that has been overwhelmingly adopted by extant species. To truly evaluate the dominance and universality of vascular optimization, however, it is critical to examine other, lesser-known, vascularized phyla. The brown algae (Phaeophyceae) are one such group--as distantly related to plants as mammals, they have convergently evolved a plant-like body plan and a specialized phloem-like transport network. To evaluate possible scaling and optimization in the kelp vascular system, we developed a model of optimized transport anatomy and tested it with measurements of the giant kelp, Macrocystis pyrifera, which is among the largest and most successful of macroalgae. We also evaluated three classical allometric relationships pertaining to plant vascular tissues with a diverse sampling of kelp species. Macrocystis pyrifera displays strong scaling relationships between all tested vascular parameters and agrees with our model; other species within the Laminariales display weak or inconsistent vascular allometries. The lack of universal scaling in the kelps and the presence of optimized transport anatomy in M. pyrifera raises important questions about the evolution of optimization and the possible competitive advantage conferred by optimized vascular systems to multicellular phyla.
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Affiliation(s)
- Sarah Tepler Drobnitch
- Department of Ecology and Evolutionary Biology, University of California, 1156 High Street, Santa Cruz, CA 95040, USA
| | - Kaare H Jensen
- Department of Physics, Technical University of Denmark, Kongens Lyngby 2800, Denmark
| | - Paige Prentice
- Department of Ecology and Evolutionary Biology, University of California, 1156 High Street, Santa Cruz, CA 95040, USA
| | - Jarmila Pittermann
- Department of Ecology and Evolutionary Biology, University of California, 1156 High Street, Santa Cruz, CA 95040, USA
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