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Anfodillo T, Olson ME. Stretched sapwood, ultra-widening permeability and ditching da Vinci: revising models of plant form and function. ANNALS OF BOTANY 2024; 134:19-42. [PMID: 38634673 PMCID: PMC11161570 DOI: 10.1093/aob/mcae054] [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: 03/22/2024] [Accepted: 04/14/2024] [Indexed: 04/19/2024]
Abstract
BACKGROUND The mechanisms leading to dieback and death of trees under drought remain unclear. To gain an understanding of these mechanisms, addressing major empirical gaps regarding tree structure-function relations remains essential. SCOPE We give reasons to think that a central factor shaping plant form and function is selection simultaneously favouring constant leaf-specific conductance with height growth and isometric (1:1) scaling between leaf area and the volume of metabolically active sink tissues ('sapwood'). Sapwood volume-leaf area isometry implies that per-leaf area sapwood volumes become transversely narrower with height growth; we call this 'stretching'. Stretching means that selection must favour increases in permeability above and beyond that afforded by tip-to-base conduit widening ("ultra-widening permeability"), via fewer and wider vessels or tracheids with larger pits or larger margo openings. Leaf area-metabolically active sink tissue isometry would mean that it is unlikely that larger trees die during drought because of carbon starvation due to greater sink-source relationships as compared to shorter plants. Instead, an increase in permeability is most plausibly associated with greater risk of embolism, and this seems a more probable explanation of the preferential vulnerability of larger trees to climate change-induced drought. Other implications of selection favouring constant per-leaf area sapwood construction and maintenance costs are departure from the da Vinci rule expectation of similar sapwood areas across branching orders, and that extensive conduit furcation in the stem seems unlikely. CONCLUSIONS Because all these considerations impact the likelihood of vulnerability to hydraulic failure versus carbon starvation, both implicated as key suspects in forest mortality, we suggest that these predictions represent essential priorities for empirical testing.
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Affiliation(s)
- Tommaso Anfodillo
- Department Territorio e Sistemi Agro-Forestali, University of Padova, Legnaro (PD) 35020, Italy
| | - Mark E Olson
- Instituto de Biología, Universidad Nacional Autónoma de México, Tercer Circuito sn de Ciudad Universitaria, Ciudad de México 04510, Mexico
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2
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Zhang Y, Pereira L, Kaack L, Liu J, Jansen S. Gold perfusion experiments support the multi-layered, mesoporous nature of intervessel pit membranes in angiosperm xylem. THE NEW PHYTOLOGIST 2024; 242:493-506. [PMID: 38404029 DOI: 10.1111/nph.19608] [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: 10/07/2023] [Accepted: 01/30/2024] [Indexed: 02/27/2024]
Abstract
Fluid transport across intervessel pit membranes of angiosperm xylem plays a major role in plant transpiration, with transport resistance largely depending on pore constriction sizes. Traditionally, fluid particles traversing pit membranes are assumed to cross a single instead of multiple pore constrictions. We tested a multi-layered pit membrane model in xylem of eight angiosperm species by estimating the size frequency of pore constrictions in relation to pit membrane thickness and compared modelled data with perfusion characteristics of nanoscale gold particles based on transmission electron microscopy. The size frequency of modelled pore constrictions showed similar patterns to the measured number of perfused particle sizes inside pit membranes, although frequency values measured were 10-50 times below modelled data. Small particles enter pit membranes most easily, especially when injected in thin pit membranes. The trapping of gold particles by pore constrictions becomes more likely with increasing pore constriction number and pit membrane thickness. While quantitative differences between modelled and experimental data are due to various practical limitations, their qualitative agreement supports a multi-layered pit membrane model with multiple pore constrictions. Pore constrictions between 5 and 50 nm are realistic, and confirm the mesoporous nature of pit membranes.
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Affiliation(s)
- Ya Zhang
- Anhui Provincial Key Laboratory of the Conservation and Exploitation of Biological Resources, College of Life Sciences, Anhui Normal University, Beijingzhong Road 2, Wuhu, 241000, China
| | - Luciano Pereira
- Institute of Botany, Ulm University, Albert-Einstein-Allee 11, Ulm, D-89081, Germany
| | - Lucian Kaack
- Institute of Botany, Ulm University, Albert-Einstein-Allee 11, Ulm, D-89081, Germany
| | - Jiabao Liu
- College of Ecology and Environment, Anhui Normal University, Beijingzhong Road 2, Wuhu, 241000, China
| | - Steven Jansen
- Institute of Botany, Ulm University, Albert-Einstein-Allee 11, Ulm, D-89081, Germany
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3
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Castelar JVS, Da Cunha M, Simioni PF, Castilhori MF, Lira-Martins D, Giles AL, Costa WS, Alexandrino CR, Callado CH. Functional traits and water-transport strategies of woody species in an insular environment in a tropical forest. AMERICAN JOURNAL OF BOTANY 2023; 110:e16214. [PMID: 37475703 DOI: 10.1002/ajb2.16214] [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: 03/01/2023] [Revised: 05/26/2023] [Accepted: 05/30/2023] [Indexed: 07/22/2023]
Abstract
PREMISE Plants survive in habitats with limited resource availability and contrasting environments by responding to variation in environmental factors through morphophysiological traits related to species performance in different ecosystems. However, how different plant strategies influence the megadiversity of tropical species has remained a knowledge gap. METHODS We analyzed variations in 27 morphophysiological traits of leaves and secondary xylem in Erythroxylum pulchrum and Tapirira guianensis, which have the highest absolute dominance in these physiognomies and occur together in areas of restinga and dense ombrophilous forest to infer water-transport strategies of Atlantic Forest woody plants. RESULTS The two species presented different sets of morphophysiological traits, strategies to avoid embolism and ensure water transport, in different phytophysiognomies. Tapirira guianensis showed possible adaptations influenced by phytophysiognomy, while E. pulchrum showed less variation in the set of characteristics between different phytophysiognomies. CONCLUSIONS Our results provide essential tools to understand how the environment can modulate morphofunctional traits and how each species adjusts differently to adapt to different phytophysiognomies. In this sense, the results for these species reveal new species-specific responses in the tropical forest. Such knowledge is a prerequisite to predict future development of the most vulnerable forests as climate changes.
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Affiliation(s)
- João Victor S Castelar
- Departamento de Biologia Vegetal, Instituto de Biologia Roberto Alcantara Gomes, Unidade de Desenvolvimento Tecnológico Laboratório de Anatomia Vegetal, Programa de Pós-Graduação em Biologia Vegetal, Universidade do Estado do Rio de Janeiro, Rio de Janeiro, RJ, Brasil
| | - Maura Da Cunha
- Laboratório de Biologia Celular e Tecidual, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos dos Goytacazes, RJ, Brasil
| | - Priscila F Simioni
- Laboratório de Biologia Celular e Tecidual, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos dos Goytacazes, RJ, Brasil
- Programa de Pós-Graduação em Ecologia e Recursos Naturais, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos dos Goytacazes, RJ, Brasil
| | - Marcelo F Castilhori
- Departamento de Biologia Vegetal, Instituto de Biologia Roberto Alcantara Gomes, Unidade de Desenvolvimento Tecnológico Laboratório de Anatomia Vegetal, Programa de Pós-Graduação em Biologia Vegetal, Universidade do Estado do Rio de Janeiro, Rio de Janeiro, RJ, Brasil
| | | | - André L Giles
- INPA - Instituto Nacional de Pesquisas da Amazônia, AM, Brasil
- Departamento de Fitotecnia, Centro de Ciência Agrárias, Universidade Federal de Santa Catarina, Florianópolis, SC
| | - Warlen S Costa
- Departamento de Biologia Vegetal, Instituto de Biologia Roberto Alcantara Gomes, Unidade de Desenvolvimento Tecnológico Laboratório de Anatomia Vegetal, Programa de Pós-Graduação em Biologia Vegetal, Universidade do Estado do Rio de Janeiro, Rio de Janeiro, RJ, Brasil
| | - Camilla R Alexandrino
- Laboratório de Biologia Celular e Tecidual, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos dos Goytacazes, RJ, Brasil
| | - Cátia H Callado
- Departamento de Biologia Vegetal, Instituto de Biologia Roberto Alcantara Gomes, Unidade de Desenvolvimento Tecnológico Laboratório de Anatomia Vegetal, Programa de Pós-Graduação em Biologia Vegetal, Universidade do Estado do Rio de Janeiro, Rio de Janeiro, RJ, Brasil
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4
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Vuerich M, Petrussa E, Boscutti F, Braidot E, Filippi A, Petruzzellis F, Tomasella M, Tromba G, Pizzuto M, Nardini A, Secchi F, Casolo V. Contrasting Responses of Two Grapevine Cultivars to Drought: The Role of Non-structural Carbohydrates in Xylem Hydraulic Recovery. PLANT & CELL PHYSIOLOGY 2023; 64:920-932. [PMID: 37384580 DOI: 10.1093/pcp/pcad066] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2023] [Revised: 05/18/2023] [Accepted: 06/26/2023] [Indexed: 07/01/2023]
Abstract
Xylem embolism is one of the possible outcomes of decreasing xylem pressure when plants face drought. Recent studies have proposed a role for non-structural carbohydrates (NSCs) in osmotic pressure generation, required for refilling embolized conduits. Potted cuttings of grapevine Grenache and Barbera, selected for their adaptation to different climatic conditions, were subjected to a drought stress followed by re-irrigation. Stem embolism rate and its recovery were monitored in vivo by X-ray micro-computed tomography (micro-CT). The same plants were further analyzed for xylem conduit dimension and NSC content. Both cultivars significantly decreased Ψpd in response to drought and recovered from xylem embolism after re-irrigation. However, although the mean vessel diameter was similar between the cultivars, Barbera was more prone to embolism. Surprisingly, vessel diameter was apparently reduced during recovery in this cultivar. Hydraulic recovery was linked to sugar content in both cultivars, showing a positive relationship between soluble NSCs and the degree of xylem embolism. However, when starch and sucrose concentrations were considered separately, the relationships showed cultivar-specific and contrasting trends. We showed that the two cultivars adopted different NSC-use strategies in response to drought, suggesting two possible scenarios driving conduit refilling. In Grenache, sucrose accumulation seems to be directly linked to embolism formation and possibly sustains refilling. In Barbera, maltose/maltodextrins could be involved in a conduit recovery strategy via the formation of cell-wall hydrogels, likely responsible for the reduction of conduit lumen detected by micro-CT.
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Affiliation(s)
- Marco Vuerich
- Dipartimento di Scienze Agroalimentari, Ambientali e Animali, Via delle Scienze 91, Udine 33100, Italy
| | - Elisa Petrussa
- Dipartimento di Scienze Agroalimentari, Ambientali e Animali, Via delle Scienze 91, Udine 33100, Italy
| | - Francesco Boscutti
- Dipartimento di Scienze Agroalimentari, Ambientali e Animali, Via delle Scienze 91, Udine 33100, Italy
| | - Enrico Braidot
- Dipartimento di Scienze Agroalimentari, Ambientali e Animali, Via delle Scienze 91, Udine 33100, Italy
| | - Antonio Filippi
- Dipartimento di Scienze Agroalimentari, Ambientali e Animali, Via delle Scienze 91, Udine 33100, Italy
- Dipartimento di Area Medica, Università di Udine, Piazzale Kolbe 4, Udine 33100, Italy
| | - Francesco Petruzzellis
- Dipartimento di Scienze della Vita, Università di Trieste, Via L. Giorgieri 10, Trieste 34127, Italy
| | - Martina Tomasella
- Dipartimento di Scienze della Vita, Università di Trieste, Via L. Giorgieri 10, Trieste 34127, Italy
| | - Giuliana Tromba
- Elettra-Sincrotrone Trieste, Area Science Park, Basovizza, Trieste 34149, Italy
| | - Mauro Pizzuto
- Vivai Cooperativi Rauscedo, Via Udine, 39, Rauscedo (PN) 33095, Italy
| | - Andrea Nardini
- Dipartimento di Scienze della Vita, Università di Trieste, Via L. Giorgieri 10, Trieste 34127, Italy
| | - Francesca Secchi
- Dipartimento di Scienze Agrarie, Forestali, Alimentari (DISAFA), Università di Torino, Largo Paolo Braccini 2, Grugliasco (TO) 10095, Italy
| | - Valentino Casolo
- Dipartimento di Scienze Agroalimentari, Ambientali e Animali, Via delle Scienze 91, Udine 33100, Italy
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5
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Chen Z, Li S, Wan X, Liu S. Strategies of tree species to adapt to drought from leaf stomatal regulation and stem embolism resistance to root properties. FRONTIERS IN PLANT SCIENCE 2022; 13:926535. [PMID: 36237513 PMCID: PMC9552884 DOI: 10.3389/fpls.2022.926535] [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: 04/22/2022] [Accepted: 09/12/2022] [Indexed: 06/16/2023]
Abstract
Considerable evidences highlight the occurrence of increasing widespread tree mortality as a result of global climate change-associated droughts. However, knowledge about the mechanisms underlying divergent strategies of various tree species to adapt to drought has remained remarkably insufficient. Leaf stomatal regulation and embolism resistance of stem xylem serves as two important strategies for tree species to prevent hydraulic failure and carbon starvation, as comprising interconnected physiological mechanisms underlying drought-induced tree mortality. Hence, the physiological and anatomical determinants of leaf stomatal regulation and stems xylem embolism resistance are evaluated and discussed. In addition, root properties related to drought tolerance are also reviewed. Species with greater investment in leaves and stems tend to maintain stomatal opening and resist stem embolism under drought conditions. The coordination between stomatal regulation and stem embolism resistance are summarized and discussed. Previous studies showed that hydraulic safety margin (HSM, the difference between minimum water potential and that causing xylem dysfunction) is a significant predictor of tree species mortality under drought conditions. Compared with HSM, stomatal safety margin (the difference between water potential at stomatal closure and that causing xylem dysfunction) more directly merge stomatal regulation strategies with xylem hydraulic strategies, illustrating a comprehensive framework to characterize plant response to drought. A combination of plant traits reflecting species' response and adaptation to drought should be established in the future, and we propose four specific urgent issues as future research priorities.
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Affiliation(s)
- Zhicheng Chen
- Key Laboratory of Forest Ecology and Environment of National Forestry and Grassland Administration, Ecology and Nature Conservation Institute, Chinese Academy of Forestry, Beijing, China
| | - Shan Li
- Department of Environmental Science and Ecology, School of Environmental Science and Engineering, Shaanxi University of Science and Technology, Xi’an, China
| | - Xianchong Wan
- Institute of Ecological Conservation and Restoration, Chinese Academy of Forestry, Beijing, China
| | - Shirong Liu
- Key Laboratory of Forest Ecology and Environment of National Forestry and Grassland Administration, Ecology and Nature Conservation Institute, Chinese Academy of Forestry, Beijing, China
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6
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Sun Q. Structural variation and spatial polysaccharide profiling of intervessel pit membranes in grapevine. ANNALS OF BOTANY 2022; 130:595-609. [PMID: 35869610 PMCID: PMC9510951 DOI: 10.1093/aob/mcac096] [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: 05/17/2022] [Accepted: 07/21/2022] [Indexed: 06/15/2023]
Abstract
BACKGROUND AND AIMS Intervessel pit membranes (PMs) are important cell wall structures in the vessel system that may impact a plant's water transport and its susceptibility to vascular diseases. Functional roles of intervessel PMs largely depend on their structure and polysaccharide composition, which are the targets of this study. METHODS With grapevine used as a model plant, this study applied an immunogold-scanning electron microscopy technique to simultaneously analyse at high resolution intervessel PM structures and major pectic and hemicellulosic polysaccharides that make up intervessel PMs. KEY RESULTS Intervessel PMs in functional xylem showed significant structural variation, with about 90 % of them being structurally intact with smooth or relatively smooth surfaces and the remaining 10 % with progressively degraded structures. The results also elucidated details of the removal process of cell wall materials from the intervessel PM surface toward its depth during its natural degradation. Four groups of pectic and hemicellulosic polysaccharides were immunolocalized in intervessel PMs and differed in their spatial distribution and abundance. Weakly methyl-esterified homogalacturonans (WMe-HGs, detected by JIM5) were abundant in the surface layer, heavily methyl-esterified homogalacturonans (HMe-HGs, detected by JIM7) and xylans detected by CCRC-M140 were mostly found in deeper layers, and fucosylated xyloglucans (F-XyGs, detected by CCRC-M1) were more uniformly distributed at different depths of the intervessel PM. CONCLUSIONS Intervessel PMs displayed diverse structural variations in grapevine. They contained certain major groups of pectic and hemicellulosic polysaccharides with different spatial distributions and abundance. This information is crucial to reveal the polysaccharide profiling of the primary cell wall and to understand the roles of intervessel PMs in the regulation of water transport as well as in a plant's susceptibility to vascular diseases.
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7
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Wagner Y, Feng F, Yakir D, Klein T, Hochberg U. In situ, direct observation of seasonal embolism dynamics in Aleppo pine trees growing on the dry edge of their distribution. THE NEW PHYTOLOGIST 2022; 235:1344-1350. [PMID: 35514143 PMCID: PMC9541785 DOI: 10.1111/nph.18208] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Accepted: 04/30/2022] [Indexed: 06/14/2023]
Abstract
Xylem embolism impairs hydraulic conductivity in trees and drives drought-induced mortality. While embolism has been monitored in vivo in potted plants, and research has revealed evidence of embolism in field-grown trees, continuous in situ monitoring of cavitation in forests is lacking. Seasonal patterns of embolism were monitored in branchlets of Aleppo pine (Pinus halepensis) trees growing in a dry Mediterranean forest. Optical visualization (OV) sensors were installed on terminal branches, in addition to monthly sampling for micro computed tomography scans. We detected 208 cavitation events among four trees, which represented an embolism increase from zero to c. 12% along the dry season. Virtually all the cavitation events occurred during daytime hours, with 77% occurring between 10:00 and 17:00 h. The probability for cavitation in a given hour increased as vapor pressure deficit (VPD) increased, up to a probability of 42% for cavitation when VPD > 5 kPa. The findings uniquely reveal the instantaneous environmental conditions that lead to cavitation. The increased likelihood of cavitation events under high VPD in water-stressed pines is the first empirical support for this long hypothesized relationship. Our observations suggest that low levels of embolism are common in Aleppo pine trees at the dry edge of their distribution.
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Affiliation(s)
- Yael Wagner
- Plant & Environmental Sciences DepartmentWeizmann Institute of ScienceRehovot7610001Israel
| | - Feng Feng
- Institute of Soil, Water and Environmental SciencesVolcani CenterARORishon Lezion7505101Israel
| | - Dan Yakir
- Earth and Planetary Science DepartmentWeizmann Institute of ScienceRehovot7610001Israel
| | - Tamir Klein
- Plant & Environmental Sciences DepartmentWeizmann Institute of ScienceRehovot7610001Israel
| | - Uri Hochberg
- Institute of Soil, Water and Environmental SciencesVolcani CenterARORishon Lezion7505101Israel
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8
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Suissa JS, Friedman WE. From cells to stems: the effects of primary vascular construction on drought-induced embolism in fern rhizomes. THE NEW PHYTOLOGIST 2021; 232:2238-2253. [PMID: 34273190 DOI: 10.1111/nph.17629] [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: 02/01/2021] [Accepted: 07/13/2021] [Indexed: 06/13/2023]
Abstract
While a considerable amount of data exists on the link between xylem construction and hydraulic function, few studies have focused on resistance to drought-induced embolism of primary vasculature in herbaceous plants. Ferns rely entirely on primary xylem and display a remarkable diversity of vascular construction in their rhizomes, making them an ideal group in which to examine hydraulic structure-function relationships. New optical methods allowed us to measure vulnerability to embolism in rhizomes, which are notoriously difficult to work with. We investigated five fern species based on their diverse xylem traits at the cellular, histological, and architectural levels. To link below- and above-ground hydraulics, we then measured leaf-stem vulnerability segmentation. Overall, rhizome vulnerability to embolism was correlated most strongly with cellular but not histological or architectural traits. Interestingly, at P6-12 , species with increased architectural dissection were actually more vulnerable to embolism, suggesting different hydraulic dynamics at low compared to high percent embolism. Importantly, leaves fully embolize before stems reach P88 , suggesting strong vulnerability segmentation. This is the first study to explore the functional implications of primary vascular construction in fern rhizomes and leaf-stem vulnerability segmentation. Strong segmentation suggests that leaves protect perennial rhizomes against severe drought stress and hydraulically induced mortality.
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Affiliation(s)
- Jacob S Suissa
- The Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, 02138, USA
- The Arnold Arboretum of Harvard University, Boston, MA, 02131, USA
| | - William E Friedman
- The Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, 02138, USA
- The Arnold Arboretum of Harvard University, Boston, MA, 02131, USA
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9
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Trade-offs among transport, support, and storage in xylem from shrubs in a semiarid chaparral environment tested with structural equation modeling. Proc Natl Acad Sci U S A 2021; 118:2104336118. [PMID: 34389676 PMCID: PMC8379947 DOI: 10.1073/pnas.2104336118] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Plant vascular systems play a central role in global water and carbon cycles and drought resistance. These vascular systems perform multiple functions that affect the fitness of plants, and trade-offs are present among these functions. Some trade-offs are well established, but studies have not examined the full suite of functions of these complex systems. Here, we used a powerful multivariate method, structural equation modeling, to test hypotheses about the trade-offs that govern this vital and globally important tissue. We show that xylem traits are broadly governed by trade-offs related to transport, mechanical support, and storage, which are rooted in cellular structure, and that the level of dehydration experienced by plants in the field exerts a strong influence over these relationships. The xylem in plants is specialized to transport water, mechanically support the plant body, and store water and carbohydrates. Balancing these functions leads to trade-offs that are linked to xylem structure. We proposed a multivariate hypothesis regarding the main xylem functions and tested it using structural equation modeling. We sampled 29 native shrub species from field sites in semiarid Southern California. We quantified xylem water transport (embolism resistance and transport efficiency), mechanical strength, storage of water (capacitance) and starch, minimum hydrostatic pressures (Pmin), and proportions of fibers, vessels, and parenchyma, which were treated as a latent variable representing “cellular trade-offs.” We found that xylem functions (transport, mechanical support, water storage, and starch storage) were independent, a result driven by Pmin. Pmin was strongly and directly or indirectly associated with all xylem functions as a hub trait. More negative Pmin was associated with increased embolism resistance and tissue strength and reduced capacitance and starch storage. We found strong support for a trade-off between embolism resistance and transport efficiency. Tissue strength was not directly associated with embolism resistance or transport efficiency, and any associations were indirect involving Pmin. With Pmin removed from the model, cellular trade-offs were central and related to all other traits. We conclude that xylem traits are broadly governed by functional trade-offs and that the Pmin experienced by plants in the field exerts a strong influence over these relationships. Angiosperm xylem contains different cell types that contribute to different functions and that underpin trade-offs.
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10
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Lemaire C, Quilichini Y, Brunel-Michac N, Santini J, Berti L, Cartailler J, Conchon P, Badel É, Herbette S. Plasticity of the xylem vulnerability to embolism in Populus tremula x alba relies on pit quantity properties rather than on pit structure. TREE PHYSIOLOGY 2021; 41:1384-1399. [PMID: 33554260 DOI: 10.1093/treephys/tpab018] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2020] [Accepted: 01/22/2021] [Indexed: 06/12/2023]
Abstract
Knowledge on variations of drought resistance traits are needed to predict the potential of trees to acclimate to coming severe drought events. Xylem vulnerability to embolism is a key parameter related to such droughts, and its phenotypic variability relies mainly on environmental plasticity. We investigated the structural determinants controlling the plasticity of vulnerability to embolism, focusing on the key elements involved in the air bubble entry in vessels, especially the intervessel pits. Poplar saplings (Populus tremula x alba (Aiton) Sm., 1804) grown in contrasted water availability or light exposure exhibited differences in the vulnerability to embolism (P50) in a range of 0.76 MPa. We then characterized the structural changes in features related to pit quantity and pit structure, from the pit ultrastructure to the organization of xylem vessels, using different microscopy techniques (transmission electron microscopy, scanning electron microscopy, light microscopy). A multispectral combination of X-ray microtomography and light microscopy analysis allowed measuring the vulnerability of each single vessel and testing some of the relationships between structural traits and vulnerability to embolism inside the xylem. The pit ultrastructure did not change, whereas the vessel dimensions increased with the vulnerability to embolism and the grouping index and fraction of intervessel cell wall both decreased with the vulnerability to embolism. These findings hold when comparing between trees or between the vessels inside the xylem of an individual tree. These results evidenced that plasticity of vulnerability to embolism in hybrid poplar occurs through changes in the pit quantity properties such as pit area and vessel grouping rather than changes on the pit structure.
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Affiliation(s)
- Cédric Lemaire
- Université Clermont Auvergne, INRAE, PIAF, F-63000 Clermont-Ferrand, France
| | - Yann Quilichini
- CNRS-Università di Corsica, UMR 6134 SPE, 20250 Corti, France
| | | | - Jérémie Santini
- CNRS-Università di Corsica, UMR 6134 SPE, 20250 Corti, France
| | - Liliane Berti
- CNRS-Università di Corsica, UMR 6134 SPE, 20250 Corti, France
| | - Julien Cartailler
- Université Clermont Auvergne, INRAE, PIAF, F-63000 Clermont-Ferrand, France
| | - Pierre Conchon
- Université Clermont Auvergne, INRAE, PIAF, F-63000 Clermont-Ferrand, France
| | - Éric Badel
- Université Clermont Auvergne, INRAE, PIAF, F-63000 Clermont-Ferrand, France
| | - Stéphane Herbette
- Université Clermont Auvergne, INRAE, PIAF, F-63000 Clermont-Ferrand, France
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11
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Avila RT, Cardoso AA, Batz TA, Kane CN, DaMatta FM, McAdam SAM. Limited plasticity in embolism resistance in response to light in leaves and stems in species with considerable vulnerability segmentation. PHYSIOLOGIA PLANTARUM 2021; 172:2142-2152. [PMID: 33942915 DOI: 10.1111/ppl.13450] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2020] [Revised: 04/23/2021] [Accepted: 04/30/2021] [Indexed: 06/12/2023]
Abstract
Xylem resistance to embolism is a key metric determining plant survival during drought. Yet, we have a limited understanding of the degree of plasticity in vulnerability to embolism. Here, we tested whether light availability influences embolism resistance in leaves and stems. The optical vulnerability method was used to assess stem and leaf resistance to embolism in Phellodendron amurense and Ilex verticillata acclimated to sun and shade microenvironments within the same canopy. In both species, we found considerable segmentation in xylem resistance to embolism between leaves and stems, but only minor acclimation in response to light availability. With the addition of a third species, Betula pubescens, which shows no vulnerability segmentation, we sought to investigate xylem anatomical traits that might correlate with strong vulnerability segmentation. We found a correlation between the area fraction of vessels in the xylem and embolism resistance across species and tissue types. Our results suggest that minimal acclimation of embolism resistance occurs in response to light environment in the same individual and that the degree of vulnerability segmentation between leaves and stems might be determined by the vessel lumen fraction of the xylem.
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Affiliation(s)
- Rodrigo T Avila
- Departamento de Biologia Vegetal, Universidade Federal de Viçosa, Viçosa, Brazil
- Department of Botany and Plant Pathology, Purdue University, West Lafayette, Indiana, USA
| | - Amanda A Cardoso
- Instituto de Ciências da Natureza, Universidade Federal de Alfenas, Alfenas, Brazil
| | - Timothy A Batz
- Department of Botany and Plant Pathology, Purdue University, West Lafayette, Indiana, USA
| | - Cade N Kane
- Department of Botany and Plant Pathology, Purdue University, West Lafayette, Indiana, USA
| | - Fábio M DaMatta
- Departamento de Biologia Vegetal, Universidade Federal de Viçosa, Viçosa, Brazil
| | - Scott A M McAdam
- Department of Botany and Plant Pathology, Purdue University, West Lafayette, Indiana, USA
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12
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Tomasella M, Casolo V, Natale S, Petruzzellis F, Kofler W, Beikircher B, Mayr S, Nardini A. Shade-induced reduction of stem nonstructural carbohydrates increases xylem vulnerability to embolism and impedes hydraulic recovery in Populus nigra. THE NEW PHYTOLOGIST 2021; 231:108-121. [PMID: 33811346 PMCID: PMC9290559 DOI: 10.1111/nph.17384] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Accepted: 03/28/2021] [Indexed: 05/08/2023]
Abstract
Nonstructural carbohydrates (NSCs) have been suggested to affect xylem transport under fluctuating water availability, but conclusive evidence is still lacking. We tested the effect of shade-induced NSC depletion on xylem vulnerability to embolism and hydraulic recovery on Populus nigra saplings. Vulnerability was assessed in light-exposed (L) and shaded (S) plants with the hydraulic method, and in vivo with the optical method and X-ray micro-computed tomography. Plants were stressed to 80% loss of hydraulic conductance (PLC) and re-irrigated to check for possible recovery. We measured PLC, bark and wood NSC content, as well as xylem sap pH, surface tension (γsap ) and sugar concentration, before, during and after drought. Shading induced depletion of stem NSC (mainly starch) reserves. All methods converged in indicating higher xylem vulnerability in S than in L plants. This difference was not explained by xylem vessel and pit anatomy or by γsap . Shading impeded sap acidification and sugar accumulation during drought in S plants and prevented hydraulic recovery, which was observed in L plants. Our results highlight the importance of stem NSCs to sustain xylem hydraulic functioning during drought and suggest that light and/or adequate stem NSC thresholds are required to trigger xylem sap chemical changes involved in embolism recovery.
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Affiliation(s)
- Martina Tomasella
- Dipartimento di Scienze della VitaUniversità di TriesteVia L. Giorgieri 10Trieste34127Italy
| | - Valentino Casolo
- Dipartimento di Scienze AgroalimentariAmbientali e AnimaliUniversità di UdineVia delle Scienze 91Udine33100Italy
| | - Sara Natale
- Dipartimento di Scienze della VitaUniversità di TriesteVia L. Giorgieri 10Trieste34127Italy
| | - Francesco Petruzzellis
- Dipartimento di Scienze della VitaUniversità di TriesteVia L. Giorgieri 10Trieste34127Italy
| | - Werner Kofler
- Department of BotanyUniversity of InnsbruckSternwartestraße 15Innsbruck6020Austria
| | - Barbara Beikircher
- Department of BotanyUniversity of InnsbruckSternwartestraße 15Innsbruck6020Austria
| | - Stefan Mayr
- Department of BotanyUniversity of InnsbruckSternwartestraße 15Innsbruck6020Austria
| | - Andrea Nardini
- Dipartimento di Scienze della VitaUniversità di TriesteVia L. Giorgieri 10Trieste34127Italy
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13
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Chen Z, Zhu S, Zhang Y, Luan J, Li S, Sun P, Wan X, Liu S. Tradeoff between storage capacity and embolism resistance in the xylem of temperate broadleaf tree species. TREE PHYSIOLOGY 2020; 40:1029-1042. [PMID: 32310276 DOI: 10.1093/treephys/tpaa046] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2019] [Accepted: 04/03/2020] [Indexed: 06/11/2023]
Abstract
Xylem traits are critical plant functional traits associated with water transport, mechanical support, and carbohydrate and water storage. Studies on the xylem hydraulic efficiency-safety tradeoff are numerous; however, the storage function of xylem parenchyma is rarely considered. The effects of a substantial number of xylem traits on water transport, embolism resistance, mechanical support, storage capacity and nonstructural carbohydrate (NSC) content were investigated in 19 temperate broadleaf species planted in an arid limestone habitat in northern China. There was no xylem hydraulic efficiency-safety tradeoff in the 19 broadleaf species. The total parenchyma fraction was negatively correlated with the fiber fraction. Embolism resistance was positively correlated with indicators of xylem mechanical strength such as vessel wall reinforcement, vessel wall thickness and fiber wall thickness, and was negatively related to the axial parenchyma fraction, especially the paratracheal parenchyma fraction. The paratracheal parenchyma fraction was positively correlated with the ratio of the paratracheal parenchyma fraction to the vessel fraction. In addition, the xylem NSC concentration was positively related to the total parenchyma fraction and axial parenchyma fraction. There was a storage capacity-embolism resistance tradeoff in the xylem of 19 broadleaf species in arid limestone habitats. We speculate that the temperate broadleaf species may show a spectrum of xylem hydraulic strategies, from the embolism resistance strategy related to a more negative P50 (the water potential corresponding to 50% loss of xylem conductivity) to the embolization repair strategy based on more paratracheal parenchyma.
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Affiliation(s)
- Zhicheng Chen
- Research Institute of Forestry New Technology, Chinese Academy of Forestry, Beijing 100091, China
| | - Shidan Zhu
- Guangxi Key Laboratory of Forest Ecology and Conservation, College of Forestry, Guangxi University, Nanning 530004, China
| | - Yongtao Zhang
- Mountain Tai Forest Ecosystem Research Station of National Forestry and Grassland Administration, Forestry College of Shandong Agricultural University, Taian 271018, China
| | - Junwei Luan
- Key Laboratory of Bamboo and Rattan Science and Technology, Institute for Resources and Environment, International Centre for Bamboo and Rattan, National Forestry and Grassland Administration, Beijing 100102, China
| | - Shan Li
- Department of Wood Anatomy and Utilization, Research Institute of Wood Industry, Chinese Academy of Forestry, Beijing 100091, China
| | - Pengsen Sun
- Key Laboratory of Forest Ecology and Environment of National Forestry and Grassland Administration, Research Institute of Forest Ecology, Environment and Protection, Chinese Academy of Forestry, Beijing 100091, China
| | - Xianchong Wan
- Research Institute of Forestry New Technology, Chinese Academy of Forestry, Beijing 100091, China
| | - Shirong Liu
- Key Laboratory of Forest Ecology and Environment of National Forestry and Grassland Administration, Research Institute of Forest Ecology, Environment and Protection, Chinese Academy of Forestry, Beijing 100091, China
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14
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Zhao H, Jiang Z, Ma J, Cai J. What causes the differences in cavitation resistance of two shrubs? Wood anatomical explanations and reliability testing of vulnerability curves. PHYSIOLOGIA PLANTARUM 2020; 169:156-168. [PMID: 31828790 DOI: 10.1111/ppl.13059] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2019] [Revised: 12/09/2019] [Accepted: 12/09/2019] [Indexed: 06/10/2023]
Abstract
Relationships between xylem anatomical traits and cavitation resistance have always been a major content of plant hydraulics. To know how plants cope with drought, it is extremely important to acquire detailed knowledge about xylem anatomical traits and assess the cavitation resistance accurately. This study aims to increase our knowledge in the methods determining cavitation resistance and xylem anatomical traits. We selected a semi-ring-porous species, Hippophae rhamnoides L., and a diffuse-porous species, Corylus heterophylla F., to clarify the reasons for the difference in cavitation resistance based on detailed xylem anatomical traits and reliable vulnerability curves (VCs). Both Cavitron and bench dehydration (BD) were used to construct VCs. Xylem anatomical traits, including pit membrane ultrastructure of these two species, were determined. The VCs obtained by the two different techniques were of different types for H. rhamnoides, its Cavitron VCs might be unreliable because of open-vessel artifacts. On the basis of BD VCs, H. rhamnoides showed higher cavitation resistance than C. heterophylla, and this is attributed to its low vessel connectivity as well as non-porous and thicker pit membranes.
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Affiliation(s)
- Han Zhao
- College of Forestry, Northwest A&F University, Yangling, 712100, China
| | - Zaimin Jiang
- College of Life Sciences, Northwest A&F University, Yangling, 712100, China
| | - Jin Ma
- College of Forestry, Northwest A&F University, Yangling, 712100, China
| | - Jing Cai
- College of Forestry, Northwest A&F University, Yangling, 712100, China
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15
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Cary KL, Ranieri GM, Pittermann J. Xylem form and function under extreme nutrient limitation: an example from California's pygmy forest. THE NEW PHYTOLOGIST 2020; 226:760-769. [PMID: 31900931 DOI: 10.1111/nph.16405] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/05/2019] [Accepted: 12/19/2019] [Indexed: 06/10/2023]
Abstract
Xylem anatomy and function have large implications for plant growth as well as survival during drought, but the impact of nutrient limitation on xylem is not fully understood. This study examines the pygmy forest in California, a plant community that experiences negligible water stress but is severely stunted by low-nutrient and acidic soil, to investigate how nutrient limitation affects xylem function. Thirteen key anatomical and hydraulic traits of stems of four species were compared between pygmy forest plants and nearby conspecifics growing on richer soil. Resistance to cavitation (P50 ), a critical trait for predicting survival during drought, had highly species-specific responses: in one species, pygmy plants had a 26% decrease in cavitation resistance compared to higher-nutrient conspecifics, while in another species, pygmy plants had a 56% increase in cavitation resistance. Other traits responded to nutrient limitation more consistently: pygmy plants had smaller xylem conduits and higher leaf-specific conductivity (KL ) than conspecific controls. Edaphic stress, even in the absence of water stress, altered xylem structure and thus had substantial impacts on water transport. Importantly, nutrient limitation shifted cavitation resistance in a species-specific and unpredictable manner; this finding has implications for the assessment of cavitation resistance in other natural systems.
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Affiliation(s)
- Katharine L Cary
- University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA, 95064, USA
| | - Gina M Ranieri
- University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA, 95064, USA
| | - Jarmila Pittermann
- University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA, 95064, USA
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16
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Park J, Go T, Ryu J, Lee SJ. Air spreading through wetted cellulose membranes: Implications for the safety function of hydraulic valves in plants. Phys Rev E 2019; 100:032409. [PMID: 31640020 DOI: 10.1103/physreve.100.032409] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2019] [Indexed: 06/10/2023]
Abstract
Plants transport water against the risk of cavitation inside xylem vessels, called "embolism." As one of their hydraulic strategies, pit membranes composed of cellulose fibers have been known as safety valves that prevent the spreading of embolism towards adjacent xylem vessels. However, detailed observation of embolism spreading through a pit membrane is still lacking. Here, we hypothesized that the pit membranes normally remain to be wetted in xylem vessels and noticed in particular the hydraulic role of water film on air spreading that has been overlooked previously. For the hydrodynamic study of the embolism spreading through a wetted pit membrane, we investigated the penetration and spreading dynamics of air plugs through the wetted cellulose membrane in a channel flow. Air spreading exhibits two types of dynamics: continuous and discrete spreading. We elucidated the correlation of dynamic characteristics of air flow and pressure variations according to membrane thickness. Our study speculates that the thickness of pit membranes affects the behaviors of water film captured by cellulose fibers, and it is a crucial criterion for the reversible gating of further spreading of embolism throughout xylem networks.
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Affiliation(s)
- JooYoung Park
- Department of Mechanical Engineering, Pohang University of Science and Technology, San 31, Hyoja-dong, Pohang 37673, South Korea
| | - Taesik Go
- Department of Mechanical Engineering, Pohang University of Science and Technology, San 31, Hyoja-dong, Pohang 37673, South Korea
| | - Jeongeun Ryu
- Department of Mechanical Engineering, Pohang University of Science and Technology, San 31, Hyoja-dong, Pohang 37673, South Korea
| | - Sang Joon Lee
- Department of Mechanical Engineering, Pohang University of Science and Technology, San 31, Hyoja-dong, Pohang 37673, South Korea
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17
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Feng J, Huang P, Wan X. Interactive effects of wind and light on growth and architecture of poplar saplings. Ecol Res 2019. [DOI: 10.1111/1440-1703.1013] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- Jinxia Feng
- Institute of New Forestry Technology Chinese Academy of Forestry Beijing China
| | - Ping Huang
- Institute of New Forestry Technology Chinese Academy of Forestry Beijing China
| | - Xianchong Wan
- Institute of New Forestry Technology Chinese Academy of Forestry Beijing China
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18
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Cardoso AA, Brodribb TJ, Lucani CJ, DaMatta FM, McAdam SAM. Coordinated plasticity maintains hydraulic safety in sunflower leaves. PLANT, CELL & ENVIRONMENT 2018; 41:2567-2576. [PMID: 29748980 DOI: 10.1111/pce.13335] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2017] [Revised: 04/17/2018] [Accepted: 04/30/2018] [Indexed: 05/13/2023]
Abstract
The xylem cavitation threshold water potential establishes a hydraulic limit on the ability of woody species to survive in water-limiting environments, but herbs may be more plastic in terms of their ability to adapt to drying conditions. Here, we examined the capacity of sunflower (Helianthus annuus L.) leaves to adapt to reduced water availability by modifying the sensitivity of xylem and stomata to soil water deficit. We found that sunflower plants grown under water-limited conditions significantly adjusted leaf osmotic potential, which was linked to a prolongation of stomatal opening as soil dried and a reduced sensitivity of photosynthesis to water-stress-induced damage. At the same time, the vulnerability of midrib xylem to water-stress-induced cavitation was observed to be highly responsive to growth conditions, with water-limited plants producing conduits with thicker cell walls which were more resistant to xylem cavitation. Coordinated plasticity in osmotic potential and xylem vulnerability enabled water-limited sunflowers to safely extract water from the soil, while protecting leaf xylem against embolism. High plasticity in sunflower xylem contrasts with data from woody plants and may suggest an alternative strategy in herbs.
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Affiliation(s)
- Amanda A Cardoso
- School of Biological Sciences, University of Tasmania, Hobart, TAS, 7001, Australia
- Departamento de Biologia Vegetal, Universidade Federal de Viçosa, Viçosa, 36570-900, MG, Brazil
- Purdue Center for Plant Biology, Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN, 47907, USA
| | - Timothy J Brodribb
- School of Biological Sciences, University of Tasmania, Hobart, TAS, 7001, Australia
| | - Christopher J Lucani
- School of Biological Sciences, University of Tasmania, Hobart, TAS, 7001, Australia
| | - Fábio M DaMatta
- Departamento de Biologia Vegetal, Universidade Federal de Viçosa, Viçosa, 36570-900, MG, Brazil
| | - Scott A M McAdam
- Purdue Center for Plant Biology, Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN, 47907, USA
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19
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Schenk HJ, Espino S, Rich-Cavazos SM, Jansen S. From the sap's perspective: The nature of vessel surfaces in angiosperm xylem. AMERICAN JOURNAL OF BOTANY 2018; 105:172-185. [PMID: 29578294 DOI: 10.1002/ajb2.1034] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2017] [Accepted: 12/14/2017] [Indexed: 06/08/2023]
Abstract
PREMISE OF THE STUDY Xylem sap in angiosperms moves under negative pressure in conduits and cell wall pores that are nanometers to micrometers in diameter, so sap is always very close to surfaces. Surfaces matter for water transport because hydrophobic ones favor nucleation of bubbles, and surface chemistry can have strong effects on flow. Vessel walls contain cellulose, hemicellulose, lignin, pectins, proteins, and possibly lipids, but what is the nature of the inner, lumen-facing surface that is in contact with sap? METHODS Vessel lumen surfaces of five angiosperms from different lineages were examined via transmission electron microscopy and confocal and fluorescence microscopy, using fluorophores and autofluorescence to detect cell wall components. Elemental composition was studied by energy-dispersive X-ray spectroscopy, and treatments with phospholipase C (PLC) were used to test for phospholipids. KEY RESULTS Vessel surfaces consisted mainly of lignin, with strong cellulose signals confined to pit membranes. Proteins were found mainly in inter-vessel pits and pectins only on outer rims of pit membranes and in vessel-parenchyma pits. Continuous layers of lipids were detected on most vessel surfaces and on most pit membranes and were shown by PLC treatment to consist at least partly of phospholipids. CONCLUSIONS Vessel surfaces appear to be wettable because lignin is not strongly hydrophobic and a coating with amphiphilic lipids would render any surface hydrophilic. New questions arise about these lipids and their possible origins from living xylem cells, especially about their effects on surface tension, surface bubble nucleation, and pit membrane function.
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Affiliation(s)
- H Jochen Schenk
- Department of Biological Science, California State University Fullerton, Fullerton, CA 92831, USA
| | - Susana Espino
- Department of Biological Science, California State University Fullerton, Fullerton, CA 92831, USA
| | - Sarah M Rich-Cavazos
- Department of Biological Science, California State University Fullerton, Fullerton, CA 92831, USA
| | - Steven Jansen
- Institute of Systematic Botany and Ecology, Ulm University, Albert-Einstein-Allee 11, D-89081, Ulm, Germany
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20
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Sellin A, Alber M, Kupper P. Increasing air humidity influences hydraulic efficiency but not functional vulnerability of xylem in hybrid aspen. JOURNAL OF PLANT PHYSIOLOGY 2017; 219:28-36. [PMID: 28985513 DOI: 10.1016/j.jplph.2017.09.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2017] [Revised: 09/18/2017] [Accepted: 09/19/2017] [Indexed: 06/07/2023]
Abstract
Climate models predict greater increases in the frequency than in the amount of precipitation and a consequent rise in atmospheric humidity at high latitudes by the end of the century. We investigated the responses of hydraulic and relevant anatomical traits of xylem to elevated relative humidity of air on a 1-yr-old coppice of hybrid aspen (Populus×wettsteinii) growing in the experimental stand at the Free Air Humidity Manipulation site in Eastern Estonia. The hydraulic conductivity of stems was measured with a high pressure flow meter; artificial cavitation in the stem segments was induced by the air injection method. Specific conductivity of xylem decreased from 4.42 in the control to 3.94kgm-1s-1MPa-1 in the humidification treatment, while the trend was well correlated with increasing wood density. Humidified trees exhibited smaller leaf area at the same xylem cross-sectional area, resulting in 34% higher average Huber values compared to the control. Control and humidity-treated trees differed by neither native embolism level nor susceptibility to dehydration-induced cavitation. Increasing atmospheric humidity reduces the hydraulic efficiency of hybrid aspen trees expressed on a xylem area basis and causes substantial changes in resource allocation between photosynthetic and water transport tissues. This climate trend does not influence stem vulnerability to cavitation.
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Affiliation(s)
- Arne Sellin
- Institute of Ecology and Earth Sciences, University of Tartu, Lai 40, 51005 Tartu, Estonia.
| | - Meeli Alber
- Institute of Ecology and Earth Sciences, University of Tartu, Lai 40, 51005 Tartu, Estonia
| | - Priit Kupper
- Institute of Ecology and Earth Sciences, University of Tartu, Lai 40, 51005 Tartu, Estonia
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21
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Venturas MD, Sperry JS, Hacke UG. Plant xylem hydraulics: What we understand, current research, and future challenges. JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2017; 59:356-389. [PMID: 28296168 DOI: 10.1111/jipb.12534] [Citation(s) in RCA: 159] [Impact Index Per Article: 22.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2017] [Accepted: 03/09/2017] [Indexed: 05/22/2023]
Abstract
Herein we review the current state-of-the-art of plant hydraulics in the context of plant physiology, ecology, and evolution, focusing on current and future research opportunities. We explain the physics of water transport in plants and the limits of this transport system, highlighting the relationships between xylem structure and function. We describe the great variety of techniques existing for evaluating xylem resistance to cavitation. We address several methodological issues and their connection with current debates on conduit refilling and exponentially shaped vulnerability curves. We analyze the trade-offs existing between water transport safety and efficiency. We also stress how little information is available on molecular biology of cavitation and the potential role of aquaporins in conduit refilling. Finally, we draw attention to how plant hydraulic traits can be used for modeling stomatal responses to environmental variables and climate change, including drought mortality.
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Affiliation(s)
- Martin D Venturas
- Department of Biology, University of Utah, 257 S 1400E, Salt Lake City, UT, 84112, USA
| | - John S Sperry
- Department of Biology, University of Utah, 257 S 1400E, Salt Lake City, UT, 84112, USA
| | - Uwe G Hacke
- Department of Renewable Resources, University of Alberta, Edmonton, AB, T6G 2E3, Canada
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22
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Hacke UG, Spicer R, Schreiber SG, Plavcová L. An ecophysiological and developmental perspective on variation in vessel diameter. PLANT, CELL & ENVIRONMENT 2017; 40:831-845. [PMID: 27304704 DOI: 10.1111/pce.12777] [Citation(s) in RCA: 106] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Revised: 05/27/2016] [Accepted: 05/31/2016] [Indexed: 05/05/2023]
Abstract
Variation in xylem vessel diameter is one of the most important parameters when evaluating plant water relations. This review provides a synthesis of the ecophysiological implications of variation in lumen diameter together with a summary of our current understanding of vessel development and its endogenous regulation. We analyzed inter-specific variation of the mean hydraulic vessel diameter (Dv ) across biomes, intra-specific variation of Dv under natural and controlled conditions, and intra-plant variation. We found that the Dv measured in young branches tends to stay below 30 µm in regions experiencing winter frost, whereas it is highly variable in the tropical rainforest. Within a plant, the widest vessels are often found in the trunk and in large roots; smaller diameters have been reported for leaves and small lateral roots. Dv varies in response to environmental factors and is not only a function of plant size. Despite the wealth of data on vessel diameter variation, the regulation of diameter is poorly understood. Polar auxin transport through the vascular cambium is a key regulator linking foliar and xylem development. Limited evidence suggests that auxin transport is also a determinant of vessel diameter. The role of auxin in cell expansion and in establishing longitudinal continuity during secondary growth deserve further study.
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Affiliation(s)
- Uwe G Hacke
- University of Alberta, Department of Renewable Resources, Edmonton, AB T6G 2E3, Canada
| | - Rachel Spicer
- Connecticut College, Department of Botany, New London, CT 06320, USA
| | - Stefan G Schreiber
- University of Alberta, Department of Renewable Resources, Edmonton, AB T6G 2E3, Canada
| | - Lenka Plavcová
- University of Hradec Králové, Department of Biology, Rokitanského 62, Hradec Králové, 500 03, Czech Republic
- Charles University, Department of Experimental Plant Biology, Viničná 5, Prague, 128 44, Czech Republic
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23
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Hillabrand RM, Hacke UG, Lieffers VJ. Drought-induced xylem pit membrane damage in aspen and balsam poplar. PLANT, CELL & ENVIRONMENT 2016; 39:2210-2220. [PMID: 27342227 DOI: 10.1111/pce.12782] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2016] [Revised: 06/13/2016] [Accepted: 06/15/2016] [Indexed: 06/06/2023]
Abstract
Drought induces an increase in a tree's vulnerability to a loss of its hydraulic conductivity in many tree species, including two common in western Canada, trembling aspen (Populus tremuloides) and balsam poplar (Populus balsamifera). Termed 'cavitation fatigue' or 'air-seeding fatigue', the mechanism of this phenomenon is not well understood, but hypothesized to be a result of damage to xylem pit membranes. To examine the validity of this hypothesis, the effect of drought on the porosity of pit membranes in aspen and balsam poplar was investigated. Controlled drought and bench dehydration treatments were used to induce fatigue and scanning electron microscopy (SEM) was used to image pit membranes for relative porosity evaluations from air-dried samples after ethanol dehydration. A significant increase in the diameter of the largest pore was found in the drought and dehydration treatments of aspen, while an increase in the percentage of porous pit membranes was found in the dehydration treatments of both species. Additionally, the location of the largest pore per pit membrane was observed to tend toward the periphery of the membrane.
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Affiliation(s)
- Rachel M Hillabrand
- University of Alberta, Department of Renewable Resources, 442 ESB, Edmonton, AB, T6G 2E3, Canada.
| | - Uwe G Hacke
- University of Alberta, Department of Renewable Resources, 442 ESB, Edmonton, AB, T6G 2E3, Canada
| | - Victor J Lieffers
- University of Alberta, Department of Renewable Resources, 442 ESB, Edmonton, AB, T6G 2E3, Canada
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24
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Venturas MD, Rodriguez-Zaccaro FD, Percolla MI, Crous CJ, Jacobsen AL, Pratt RB. Single vessel air injection estimates of xylem resistance to cavitation are affected by vessel network characteristics and sample length. TREE PHYSIOLOGY 2016; 36:1247-1259. [PMID: 27358206 DOI: 10.1093/treephys/tpw055] [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: 02/12/2016] [Accepted: 05/30/2016] [Indexed: 06/06/2023]
Abstract
Xylem resistance to cavitation is an important trait that is related to the ecology and survival of plant species. Vessel network characteristics, such as vessel length and connectivity, could affect the spread of emboli from gas-filled vessels to functional ones, triggering their cavitation. We hypothesized that the cavitation resistance of xylem vessels is randomly distributed throughout the vessel network. We predicted that single vessel air injection (SVAI) vulnerability curves (VCs) would thus be affected by sample length. Longer stem samples were predicted to appear more resistant than shorter samples due to the sampled path including greater numbers of vessels. We evaluated the vessel network characteristics of grapevine (Vitis vinifera L.), English oak (Quercus robur L.) and black cottonwood (Populus trichocarpa Torr. & A. Gray), and constructed SVAI VCs for 5- and 20-cm-long segments. We also constructed VCs with a standard centrifuge method and used computer modelling to estimate the curve shift expected for pathways composed of different numbers of vessels. For all three species, the SVAI VCs for 5 cm segments rose exponentially and were more vulnerable than the 20 cm segments. The 5 cm curve shapes were exponential and were consistent with centrifuge VCs. Modelling data supported the observed SVAI VC shifts, which were related to path length and vessel network characteristics. These results suggest that exponential VCs represent the most realistic curve shape for individual vessel resistance distributions for these species. At the network level, the presence of some vessels with a higher resistance to cavitation may help avoid emboli spread during tissue dehydration.
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Affiliation(s)
- Martin D Venturas
- Department of Biology, California State University, Bakersfield, 9001 Stockdale Hwy, Bakersfield, CA 93311, USA
- Forest Genetics and Ecophysiology Research Group (GENFOR), School of Forest Engineering, Technical University of Madrid, 28040 Madrid, Spain
| | - F Daniela Rodriguez-Zaccaro
- Department of Biology, California State University, Bakersfield, 9001 Stockdale Hwy, Bakersfield, CA 93311, USA
| | - Marta I Percolla
- Department of Biology, California State University, Bakersfield, 9001 Stockdale Hwy, Bakersfield, CA 93311, USA
| | - Casparus J Crous
- Forestry and Agricultural Biotechnology Institute, University of Pretoria, Lynnwood Road & Roper Street, Hatfield, Pretoria 0002, South Africa
| | - Anna L Jacobsen
- Department of Biology, California State University, Bakersfield, 9001 Stockdale Hwy, Bakersfield, CA 93311, USA
| | - R Brandon Pratt
- Department of Biology, California State University, Bakersfield, 9001 Stockdale Hwy, Bakersfield, CA 93311, USA
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Grönlund L, Hölttä T, Mäkelä A. Branch age and light conditions determine leaf-area-specific conductivity in current shoots of Scots pine. TREE PHYSIOLOGY 2016; 36:994-1006. [PMID: 27217528 DOI: 10.1093/treephys/tpw041] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2015] [Accepted: 04/17/2016] [Indexed: 06/05/2023]
Abstract
Shoot size and other shoot properties more or less follow the availability of light, but there is also evidence that the topological position in a tree crown has an influence on shoot development. Whether the hydraulic properties of new shoots are more regulated by the light or the position affects the shoot acclimation to changing light conditions and thereby to changing evaporative demand. We investigated the leaf-area-specific conductivity (and its components sapwood-specific conductivity and Huber value) of the current-year shoots of Scots pine (Pinus sylvestris L.) in relation to light environment and topological position in three different tree classes. The light environment was quantified in terms of simulated transpiration and the topological position was quantified by parent branch age. Sample shoot measurements included length, basal and tip diameter, hydraulic conductivity of the shoot, tracheid area and density, and specific leaf area. In our results, the leaf-area-specific conductivity of new shoots declined with parent branch age and increased with simulated transpiration rate of the shoot. The relation to transpiration demand seemed more decisive, since it gave higher R(2) values than branch age and explained the differences between the tree classes. The trend of leaf-area-specific conductivity with simulated transpiration was closely related to Huber value, whereas the trend of leaf-area-specific conductivity with parent branch age was related to a similar trend in sapwood-specific conductivity.
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Affiliation(s)
- Leila Grönlund
- Department of Forest Sciences, University of Helsinki, Post Office Box 27, Helsinki FI-00014, Finland
| | - Teemu Hölttä
- Department of Forest Sciences, University of Helsinki, Post Office Box 27, Helsinki FI-00014, Finland
| | - Annikki Mäkelä
- Department of Forest Sciences, University of Helsinki, Post Office Box 27, Helsinki FI-00014, Finland
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26
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Gleason SM, Westoby M, Jansen S, Choat B, Hacke UG, Pratt RB, Bhaskar R, Brodribb TJ, Bucci SJ, Cao KF, Cochard H, Delzon S, Domec JC, Fan ZX, Feild TS, Jacobsen AL, Johnson DM, Lens F, Maherali H, Martínez-Vilalta J, Mayr S, McCulloh KA, Mencuccini M, Mitchell PJ, Morris H, Nardini A, Pittermann J, Plavcová L, Schreiber SG, Sperry JS, Wright IJ, Zanne AE. Weak tradeoff between xylem safety and xylem-specific hydraulic efficiency across the world's woody plant species. THE NEW PHYTOLOGIST 2016; 209:123-36. [PMID: 26378984 DOI: 10.1111/nph.13646] [Citation(s) in RCA: 283] [Impact Index Per Article: 35.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2015] [Accepted: 08/13/2015] [Indexed: 05/18/2023]
Abstract
The evolution of lignified xylem allowed for the efficient transport of water under tension, but also exposed the vascular network to the risk of gas emboli and the spread of gas between xylem conduits, thus impeding sap transport to the leaves. A well-known hypothesis proposes that the safety of xylem (its ability to resist embolism formation and spread) should trade off against xylem efficiency (its capacity to transport water). We tested this safety-efficiency hypothesis in branch xylem across 335 angiosperm and 89 gymnosperm species. Safety was considered at three levels: the xylem water potentials where 12%, 50% and 88% of maximal conductivity are lost. Although correlations between safety and efficiency were weak (r(2) < 0.086), no species had high efficiency and high safety, supporting the idea for a safety-efficiency tradeoff. However, many species had low efficiency and low safety. Species with low efficiency and low safety were weakly associated (r(2) < 0.02 in most cases) with higher wood density, lower leaf- to sapwood-area and shorter stature. There appears to be no persuasive explanation for the considerable number of species with both low efficiency and low safety. These species represent a real challenge for understanding the evolution of xylem.
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Affiliation(s)
- Sean M Gleason
- Department of Biological Sciences, Macquarie University, Sydney, NSW, 2109, Australia
- USDA-ARS, Water Management Research, 2150 Center Ave, Build D, Suite 320, Fort Collins, CO, 80526, USA
| | - Mark Westoby
- Department of Biological Sciences, Macquarie University, Sydney, NSW, 2109, Australia
| | - Steven Jansen
- Institute of Systematic Botany and Ecology, Ulm University, Albert-Einstein-Allee 11, 89081, Ulm, Germany
| | - Brendan Choat
- Hawkesbury Institute for the Environment, Western Sydney University, Richmond, NSW, 2753, Australia
| | - Uwe G Hacke
- Department of Renewable Resources, University of Alberta, Edmonton, AB T6G 2E3, Canada
| | - Robert B Pratt
- Department of Biology, California State University, Bakersfield, CA, 93311, USA
| | - Radika Bhaskar
- Department of Biology, Haverford College, 370 Lancaster Avenue, Haverford, PA, 19041, USA
| | - Tim J Brodribb
- School of Biological Sciences, University of Tasmania, Hobart, Tasmania, 7001, Australia
| | - Sandra J Bucci
- Grupo de Estudios Biofísicos y Eco-fisiológicos (GEBEF), Universidad Nacional de la Patagonia San Juan Bosco, 9000, Comodoro Rivadavia, Argentina
| | - Kun-Fang Cao
- Plant Ecophysiology and Evolution Group, State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, and College of Forestry, Guangxi University, Daxuedonglu 100, Nanning, Guangxi, 530004, China
| | - Hervé Cochard
- INRA, UMR547 PIAF, F-63100, Clermont-Ferrand, France
- Clermont Université, Université Blaise Pascal, UMR547 PIAF, F-63000, Clermont-Ferrand, France
| | - Sylvain Delzon
- INRA, University of Bordeaux, UMR BIOGECO, F-33450, Talence, France
| | - Jean-Christophe Domec
- Bordeaux Sciences AGRO, UMR1391 ISPA INRA, 1 Cours du général de Gaulle, 33175, Gradignan Cedex, France
- Nicholas School of the Environment, Duke University, Durham, NC, 27708, USA
| | - Ze-Xin Fan
- Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan, 666303, China
| | - Taylor S Feild
- School of Marine and Tropical Biology, James Cook University, Townsville, Qld, 4811, Australia
| | - Anna L Jacobsen
- Department of Biology, California State University, Bakersfield, CA, 93311, USA
| | - Daniel M Johnson
- Department of Forest, Rangeland and Fire Sciences, University of Idaho, Moscow, ID, 83844, USA
| | - Frederic Lens
- Naturalis Biodiversity Center, Leiden University, PO Box 9517, 2300RA, Leiden, the Netherlands
| | - Hafiz Maherali
- Department of Integrative Biology, University of Guelph, Guelph, Ontario, N1G2W1, Canada
| | - Jordi Martínez-Vilalta
- CREAF, Cerdanyola del Vallès, E-08193, Barcelona, Spain
- ICREA at CREAF, Cerdanyola del Vallès, E-08193, Barcelona, Spain
| | - Stefan Mayr
- Department of Botany, University of Innsbruck, Sternwartestr. 15, 6020, Innsbruck, Austria
| | | | - Maurizio Mencuccini
- ICREA at CREAF, Cerdanyola del Vallès, E-08193, Barcelona, Spain
- School of GeoSciences, University of Edinburgh, Crew Building, West Mains Road, Edinburgh, EH9 3FF, UK
| | | | - Hugh Morris
- Institute of Systematic Botany and Ecology, Ulm University, Albert-Einstein-Allee 11, 89081, Ulm, Germany
| | - Andrea Nardini
- Dipartimento Scienze della Vita, Università Trieste, Via L. Giorgieri 10, 34127, Trieste, Italy
| | - Jarmila Pittermann
- Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, CA, 95064, USA
| | - Lenka Plavcová
- Institute of Systematic Botany and Ecology, Ulm University, Albert-Einstein-Allee 11, 89081, Ulm, Germany
- Department of Renewable Resources, University of Alberta, Edmonton, AB T6G 2E3, Canada
| | - Stefan G Schreiber
- Department of Renewable Resources, University of Alberta, Edmonton, AB T6G 2E3, Canada
| | - John S Sperry
- Department of Biology, University of Utah, 257S 1400E, Salt Lake City, UT, 84112, USA
| | - Ian J Wright
- Department of Biological Sciences, Macquarie University, Sydney, NSW, 2109, Australia
| | - Amy E Zanne
- Department of Biological Sciences, George Washington University, Science and Engineering Hall, 800 22nd Street NW, Suite 6000, Washington, DC, 20052, USA
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Schulte PJ, Hacke UG, Schoonmaker AL. Pit membrane structure is highly variable and accounts for a major resistance to water flow through tracheid pits in stems and roots of two boreal conifer species. THE NEW PHYTOLOGIST 2015; 208:102-13. [PMID: 25944400 DOI: 10.1111/nph.13437] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2015] [Accepted: 03/29/2015] [Indexed: 05/22/2023]
Abstract
The flow of xylem sap in conifers is strongly dependent on the presence of a low resistance path through bordered pits, particularly through the pores present in the margo of the pit membrane. A computational fluid dynamics approach was taken, solving the Navier-Stokes equation for models based on the geometry of pits observed in tracheids from stems and roots of Picea mariana (black spruce) and Picea glauca (white spruce). Model solutions demonstrate a close, inverse relationship between the total resistance of bordered pits and the total area of margo pores. Flow through the margo was dominated by a small number of the widest pores. Particularly for pits where the margo component of flow resistance was low relative to that of the torus, pore location near the inner edge of the margo allowed for greater flow than that occurring through similar-sized pores near the outer edge of the margo. Results indicate a surprisingly large variation in pit structure and flow characteristics. Nonetheless, pits in roots have lower resistance to flow than those in stems because the pits were wider and consisted of a margo with a larger area in pores.
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Affiliation(s)
- Paul J Schulte
- School of Life Sciences, University of Nevada - Las Vegas, Las Vegas, NV, 89154, USA
| | - Uwe G Hacke
- Department of Renewable Resources, University of Alberta, Edmonton, AB, Canada
| | - Amanda L Schoonmaker
- Boreal Research Institute, Northern Alberta Institute of Technology, Peace River, AB, Canada
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Fichot R, Brignolas F, Cochard H, Ceulemans R. Vulnerability to drought-induced cavitation in poplars: synthesis and future opportunities. PLANT, CELL & ENVIRONMENT 2015; 38:1233-51. [PMID: 25444560 DOI: 10.1111/pce.12491] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2014] [Accepted: 11/12/2014] [Indexed: 05/04/2023]
Abstract
Vulnerability to drought-induced cavitation is a key trait of plant water relations. Here, we summarize the available literature on vulnerability to drought-induced cavitation in poplars (Populus spp.), a genus of agronomic, ecological and scientific importance. Vulnerability curves and vulnerability parameters (including the water potential inducing 50% loss in hydraulic conductivity, P50) were collected from 37 studies published between 1991 and 2014, covering a range of 10 species and 12 interspecific hybrid crosses. Results of our meta-analysis confirm that poplars are among the most vulnerable woody species to drought-induced cavitation (mean P50 = -1.44 and -1.55 MPa across pure species and hybrids, respectively). Yet, significant variation occurs among species (P50 range: 1.43 MPa) and among hybrid crosses (P50 range: 1.12 MPa), within species and hybrid crosses (max. P50 range reported: 0.8 MPa) as well as in response to environmental factors including nitrogen fertilization, irradiance, temperature and drought (max. P50 range reported: 0.75 MPa). Potential implications and gaps in knowledge are discussed in the context of poplar cultivation, species adaptation and climate modifications. We suggest that poplars represent a valuable model for studies on drought-induced cavitation, especially to elucidate the genetic and molecular basis of cavitation resistance in Angiosperms.
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Affiliation(s)
- Régis Fichot
- INRA, LBLGC, EA 1207, University of Orléans, Orléans, F-45067, France
| | - Franck Brignolas
- INRA, LBLGC, EA 1207, University of Orléans, Orléans, F-45067, France
| | - Hervé Cochard
- UMR547 PIAF, INRA, Clermont-Ferrand, F-63100, France
- UMR547 PIAF, Clermont Université, Université Blaise-Pascal, Clermont-Ferrand, F-63000, France
| | - Reinhart Ceulemans
- Department of Biology, Centre of Excellence, Plant and Vegetation Ecology (PLECO), University of Antwerp, Wilrijk, B-2610, Belgium
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Schoonmaker AL, Lieffers VJ, Landhäusser SM. Uniform versus asymmetric shading mediates crown recession in conifers. PLoS One 2014; 9:e104187. [PMID: 25136823 PMCID: PMC4138101 DOI: 10.1371/journal.pone.0104187] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2014] [Accepted: 07/11/2014] [Indexed: 11/30/2022] Open
Abstract
In this study we explore the impact of asymmetrical vs. uniform crown shading on the mortality and growth of upper and lower branches within tree crowns, for two conifer species: shade intolerant lodgepole pine (Pinus contorta) and shade tolerant white spruce (Picea glauca). We also explore xylem hydraulics, foliar nutrition, and carbohydrate status as drivers for growth and expansion of the lower and upper branches in various types of shading. This study was conducted over a two-year period across 10 regenerating forest sites dominated by lodgepole pine and white spruce, in the lower foothills of Alberta, Canada. Trees were assigned to one of four shading treatments: (1), complete uniform shading of the entire tree, (2) light asymmetric shading where the lower 1/4–1/3 of the tree crown was shaded, (3) heavy asymmetric shading as in (2) except with greater light reduction and (4) control in which no artificial shading occurred and most of the entire crown was exposed to full light. Asymmetrical shading of only the lower crown had a larger negative impact on the bud expansion and growth than did uniform shading, and the effect was stronger in pine relative to spruce. In addition, lower branches in pine also had lower carbon reserves, and reduced xylem-area specific conductivity compared to spruce. For both species, but particularly the pine, the needles of lower branches tended to store less C than upper branches in the asymmetric shade, which could suggest a movement of reserves away from the lower branches. The implications of these findings correspond with the inherent shade tolerance and self-pruning behavior of these conifers and supports a carbon based mechanism for branch mortality – mediated by an asymmetry in light exposure of the crown.
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Affiliation(s)
- Amanda L. Schoonmaker
- Boreal Research Institute, Northern Alberta Institute of Technology, Peace River, Alberta, Canada
- * E-mail:
| | - Victor J. Lieffers
- Department of Renewable Resources, University of Alberta, Edmonton, Alberta, Canada
| | - Simon M. Landhäusser
- Department of Renewable Resources, University of Alberta, Edmonton, Alberta, Canada
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30
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Tixier A, Herbette S, Jansen S, Capron M, Tordjeman P, Cochard H, Badel E. Modelling the mechanical behaviour of pit membranes in bordered pits with respect to cavitation resistance in angiosperms. ANNALS OF BOTANY 2014; 114:325-34. [PMID: 24918205 PMCID: PMC4111388 DOI: 10.1093/aob/mcu109] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2014] [Accepted: 04/25/2014] [Indexed: 05/03/2023]
Abstract
BACKGROUND AND AIMS Various correlations have been identified between anatomical features of bordered pits in angiosperm xylem and vulnerability to cavitation, suggesting that the mechanical behaviour of the pits may play a role. Theoretical modelling of the membrane behaviour has been undertaken, but it requires input of parameters at the nanoscale level. However, to date, no experimental data have indicated clearly that pit membranes experience strain at high levels during cavitation events. METHODS Transmission electron microscopy (TEM) was used in order to quantify the pit micromorphology of four tree species that show contrasting differences in vulnerability to cavitation, namely Sorbus aria, Carpinus betulus, Fagus sylvatica and Populus tremula. This allowed anatomical characters to be included in a mechanical model that was based on the Kirchhoff-Love thin plate theory. A mechanistic model was developed that included the geometric features of the pits that could be measured, with the purpose of evaluating the pit membrane strain that results from a pressure difference being applied across the membrane. This approach allowed an assessment to be made of the impact of the geometry of a pit on its mechanical behaviour, and provided an estimate of the impact on air-seeding resistance. KEY RESULTS The TEM observations showed evidence of residual strains on the pit membranes, thus demonstrating that this membrane may experience a large degree of strain during cavitation. The mechanical modelling revealed the interspecific variability of the strains experienced by the pit membrane, which varied according to the pit geometry and the pressure experienced. The modelling output combined with the TEM observations suggests that cavitation occurs after the pit membrane has been deflected against the pit border. Interspecific variability of the strains experienced was correlated with vulnerability to cavitation. Assuming that air-seeding occurs at a given pit membrane strain, the pressure predicted by the model to achieve this mechanical state corresponds to experimental values of cavitation sensitivity (P50). CONCLUSIONS The results provide a functional understanding of the importance of pit geometry and pit membrane structure in air-seeding, and thus in vulnerability to cavitation.
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Affiliation(s)
- Aude Tixier
- Clermont Université, Université Blaise Pascal, UMR 547 PIAF, 63000 Clermont-Ferrand, France INRA, UMR 547 PIAF, 63100 Clermont-Ferrand, France
| | - Stephane Herbette
- Clermont Université, Université Blaise Pascal, UMR 547 PIAF, 63000 Clermont-Ferrand, France INRA, UMR 547 PIAF, 63100 Clermont-Ferrand, France
| | - Steven Jansen
- Institute for Systematic Botany and Ecology, Ulm University, Albert-Einstein-Allee 11, D-89081 Ulm, Germany
| | - Marie Capron
- Université de Toulouse, INPT-CNRS, Institut de Mécanique des Fluides de Toulouse, Allée du Professeur C. Soula, F-31400 Toulouse, France
| | - Philippe Tordjeman
- Université de Toulouse, INPT-CNRS, Institut de Mécanique des Fluides de Toulouse, Allée du Professeur C. Soula, F-31400 Toulouse, France
| | - Hervé Cochard
- Clermont Université, Université Blaise Pascal, UMR 547 PIAF, 63000 Clermont-Ferrand, France INRA, UMR 547 PIAF, 63100 Clermont-Ferrand, France
| | - Eric Badel
- Clermont Université, Université Blaise Pascal, UMR 547 PIAF, 63000 Clermont-Ferrand, France INRA, UMR 547 PIAF, 63100 Clermont-Ferrand, France
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Ryu J, Ahn S, Kim SG, Kim T, Lee SJ. Interactive ion-mediated sap flow regulation in olive and laurel stems: physicochemical characteristics of water transport via the pit structure. PLoS One 2014; 9:e98484. [PMID: 24852943 PMCID: PMC4031214 DOI: 10.1371/journal.pone.0098484] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2014] [Accepted: 05/02/2014] [Indexed: 11/18/2022] Open
Abstract
Sap water is distributed and utilized through xylem conduits, which are vascular networks of inert pipes important for plant survival. Interestingly, plants can actively regulate water transport using ion-mediated responses and adapt to environmental changes. However, ionic effects on active water transport in vascular plants remain unclear. In this report, the interactive ionic effects on sap transport were systematically investigated for the first time by visualizing the uptake process of ionic solutions of different ion compositions (K+/Ca2+) using synchrotron X-ray and neutron imaging techniques. Ionic solutions with lower K+/Ca2+ ratios induced an increased sap flow rate in stems of Olea europaea L. and Laurus nobilis L. The different ascent rates of ionic solutions depending on K+/Ca2+ ratios at a fixed total concentration increases our understanding of ion-responsiveness in plants from a physicochemical standpoint. Based on these results, effective structural changes in the pit membrane were observed using varying ionic ratios of K+/Ca2+. The formation of electrostatically induced hydrodynamic layers and the ion-responsiveness of hydrogel structures based on Hofmeister series increase our understanding of the mechanism of ion-mediated sap flow control in plants.
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Affiliation(s)
- Jeongeun Ryu
- Department of Mechanical Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk, Republic of Korea
- Center for Biofluid and Biomimic Research, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk, Republic of Korea
| | - Sungsook Ahn
- Department of Mechanical Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk, Republic of Korea
- Center for Biofluid and Biomimic Research, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk, Republic of Korea
| | - Seung-Gon Kim
- Department of Mechanical Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk, Republic of Korea
- Center for Biofluid and Biomimic Research, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk, Republic of Korea
| | - TaeJoo Kim
- Neutron Science Division, Korea Atomic Energy Research Institute (KAERI), Daejeon, Republic of Korea
| | - Sang Joon Lee
- Department of Mechanical Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk, Republic of Korea
- Center for Biofluid and Biomimic Research, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk, Republic of Korea
- * E-mail:
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Rockwell FE, Wheeler JK, Holbrook NM. Cavitation and its discontents: opportunities for resolving current controversies. PLANT PHYSIOLOGY 2014; 164:1649-60. [PMID: 24501002 PMCID: PMC3982731 DOI: 10.1104/pp.113.233817] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2013] [Accepted: 02/02/2014] [Indexed: 05/18/2023]
Abstract
Cavitation has long been recognized as a key constraint on the structure and functional integrity of the xylem. Yet, recent results call into question how well we understand cavitation in plants. Here, we consider embolism formation in angiosperms at two scales. The first focuses on how air-seeding occurs at the level of pit membranes, raising the question of whether capillary failure is an appropriate physical model. The second addresses methodological uncertainties that affect our ability to infer the formation of embolism and its reversal in plant stems. Overall, our goal is to open up fresh perspectives on the structure-function relationships of xylem.
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Affiliation(s)
- Fulton E. Rockwell
- School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York 14853 (F.E.R.); and
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts 02138 (J.K.W., N.M.H.)
| | - James K. Wheeler
- School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York 14853 (F.E.R.); and
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts 02138 (J.K.W., N.M.H.)
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Dusotoit-Coucaud A, Brunel N, Tixier A, Cochard H, Herbette S. Hydrolase treatments help unravel the function of intervessel pits in xylem hydraulics. PHYSIOLOGIA PLANTARUM 2014; 150:388-396. [PMID: 23981110 DOI: 10.1111/ppl.12092] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2013] [Revised: 06/18/2013] [Accepted: 07/14/2013] [Indexed: 06/02/2023]
Abstract
Intervessel pits are structures that play a key role in the efficiency and safety functions of xylem hydraulics. However, little is known about the components of the pit membrane (PM) and their role in hydraulic functions, especially in resistance to cavitation. We tested the effect of commercial chemicals including a cellulase, a hemicellulase, a pectolyase, a proteinase and DTT on xylem hydraulic properties: vulnerability to cavitation (VC) and conductance. The effects were tested on branch segments from Fagus sylvatica (where the effects on pit structure were analyzed using TEM) and Populus tremula. Cellulose hydrolysis resulted in a sharp increase in VC and a significant increase in conductance, related to complete breakdown of the PM. Pectin hydrolysis also induced a sharp increase in VC but with no effect on conductance or pit structure observable by TEM. The other treatments with hemicellulase, proteinase or DTT showed no effect. This study brings evidence that cellulose and pectins are critical components underpinning VC, and that PM components may play distinct roles in the xylem hydraulic safety and efficiency.
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Affiliation(s)
- Anaïs Dusotoit-Coucaud
- INRA, UMR547 PIAF, 5 Chemin de Beaulieu, 63039, Clermont-Ferrand, Cedex 02, France; Clermont Université, Université Blaise-Pascal, UMR547 PIAF, BP 10448, 63000, Clermont-Ferrand, France
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34
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Affiliation(s)
- Uwe G Hacke
- Department of Renewable Resources, University of Alberta, Edmonton, AB T6G 2E3, Canada
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35
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Scholz A, Rabaey D, Stein A, Cochard H, Smets E, Jansen S. The evolution and function of vessel and pit characters with respect to cavitation resistance across 10 Prunus species. TREE PHYSIOLOGY 2013; 33:684-694. [PMID: 23933827 DOI: 10.1093/treephys/tpt050] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Various structure-function relationships regarding drought-induced cavitation resistance of secondary xylem have been postulated. These hypotheses were tested on wood of 10 Prunus species showing a range in P50 (i.e., the pressure corresponding to 50% loss of hydraulic conductivity) from -3.54 to -6.27 MPa. Hydraulically relevant wood characters were quantified using light and electron microscopy. A phylogenetic tree was constructed to investigate evolutionary correlations using a phylogenetically independent contrast (PIC) analysis. Vessel-grouping characters were found to be most informative in explaining interspecific variation in P50, with cavitation-resistant species showing more solitary vessels than less resistant species. Co-evolution between vessel-grouping indices and P50 was reported. P50 was weakly correlated with the shape of the intervessel pit aperture, but not with the total intervessel pit membrane area per vessel. A negative correlation was found between P50 and intervessel pit membrane thickness, but this relationship was not supported by the PIC analysis. Cavitation resistance has co-evolved with vessel grouping within Prunus and was mainly influenced by the spatial distribution of the vessel network.
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Affiliation(s)
- Alexander Scholz
- Institute for Systematic Botany and Ecology, Ulm University, Albert-Einstein-Allee 11, D-89081 Ulm, Germany
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36
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Lens F, Tixier A, Cochard H, Sperry JS, Jansen S, Herbette S. Embolism resistance as a key mechanism to understand adaptive plant strategies. CURRENT OPINION IN PLANT BIOLOGY 2013; 16:287-92. [PMID: 23453076 DOI: 10.1016/j.pbi.2013.02.005] [Citation(s) in RCA: 100] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2013] [Accepted: 02/07/2013] [Indexed: 05/21/2023]
Abstract
One adaptation of plants to cope with drought or frost stress is to develop wood that is able to withstand the formation and distribution of air bubbles (emboli) in its water conducting xylem cells under negative pressure. The ultrastructure of interconduit pits strongly affects drought-induced embolism resistance, but also mechanical properties of the xylem are involved. The first experimental evidence for a lower embolism resistance in stems of herbaceous plants compared to stems of their secondarily woody descendants further supports this mechanical-functional trade-off. An integrative approach combining (ultra)structural observations of the xylem, safety-efficiency aspects of the hydraulic pipeline, and xylem-phloem interactions will shed more light on the multiple adaptive strategies of embolism resistance in plants.
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Affiliation(s)
- Frederic Lens
- Naturalis Biodiversity Center, Leiden University, P.O. Box 9514, NL-2300 RA Leiden, The Netherlands.
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Scholz A, Klepsch M, Karimi Z, Jansen S. How to quantify conduits in wood? FRONTIERS IN PLANT SCIENCE 2013; 4:56. [PMID: 23507674 PMCID: PMC3600434 DOI: 10.3389/fpls.2013.00056] [Citation(s) in RCA: 92] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2012] [Accepted: 02/28/2013] [Indexed: 05/02/2023]
Abstract
Vessels and tracheids represent the most important xylem cells with respect to long distance water transport in plants. Wood anatomical studies frequently provide several quantitative details of these cells, such as vessel diameter, vessel density, vessel element length, and tracheid length, while important information on the three dimensional structure of the hydraulic network is not considered. This paper aims to provide an overview of various techniques, although there is no standard protocol to quantify conduits due to high anatomical variation and a wide range of techniques available. Despite recent progress in image analysis programs and automated methods for measuring cell dimensions, density, and spatial distribution, various characters remain time-consuming and tedious. Quantification of vessels and tracheids is not only important to better understand functional adaptations of tracheary elements to environment parameters, but will also be essential for linking wood anatomy with other fields such as wood development, xylem physiology, palaeobotany, and dendrochronology.
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Affiliation(s)
- Alexander Scholz
- Institute for Systematic Botany and Ecology, Ulm UniversityUlm, Germany
| | - Matthias Klepsch
- Institute for Systematic Botany and Ecology, Ulm UniversityUlm, Germany
| | - Zohreh Karimi
- Institute for Systematic Botany and Ecology, Ulm UniversityUlm, Germany
- Golestan UniversityGorgan, Iran
| | - Steven Jansen
- Institute for Systematic Botany and Ecology, Ulm UniversityUlm, Germany
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Plavcová L, Hacke UG, Almeida-Rodriguez AM, Li E, Douglas CJ. Gene expression patterns underlying changes in xylem structure and function in response to increased nitrogen availability in hybrid poplar. PLANT, CELL & ENVIRONMENT 2013; 36:186-99. [PMID: 22734437 DOI: 10.1111/j.1365-3040.2012.02566.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Nitrogen availability has a strong influence on plant growth and development. In this study, we examined the effect of nitrogen availability on xylogenesis in hybrid poplar (Populus trichocarpa x deltoides H11-11). Saplings of hybrid poplar were fertilized for 33 d with either high or adequate levels of ammonium nitrate. We observed enhanced radial growth, wider vessels and fibres and thinner fibre walls in the secondary xylem of high N relative to adequate N plants. These anatomical differences translated into altered hydraulic properties with xylem being more transport efficient but also more vulnerable to drought-induced cavitation in high N plants. The changes in xylem structure and function were associated with differences in gene expression as revealed by the transcriptome analysis of the developing xylem region. We found 388 genes differentially expressed (fold change ±1.5, P-value ≤ 0.05), including a number of genes putatively involved in nitrogen and carbohydrate metabolism and various aspects of xylem cell differentiation. Several genes encoding known transcriptional regulators of secondary cell wall deposition were down-regulated in high N plants, corresponding with thinner secondary cell walls in these plants. The results of this study provide us with gene candidates potentially affecting xylem hydraulic and structural traits.
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Affiliation(s)
- Lenka Plavcová
- Department of Renewable Resources, University of Alberta, Edmonton, Alberta, Canada.
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Plavcová L, Jansen S, Klepsch M, Hacke UG. Nobody's perfect: can irregularities in pit structure influence vulnerability to cavitation? FRONTIERS IN PLANT SCIENCE 2013; 4:453. [PMID: 24273549 PMCID: PMC3824106 DOI: 10.3389/fpls.2013.00453] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2013] [Accepted: 10/22/2013] [Indexed: 05/04/2023]
Abstract
Recent studies have suggested that species-specific pit properties such as pit membrane thickness, pit membrane porosity, torus-to-aperture diameter ratio and pit chamber depth influence xylem vulnerability to cavitation. Despite the indisputable importance of using mean pit characteristics, considerable variability in pit structure within a single species or even within a single pit field should be acknowledged. According to the rare pit hypothesis, a single pit that is more air-permeable than many neighboring pits is sufficient to allow air-seeding. Therefore, any irregularities or morphological abnormalities in pit structure allowing air-seeding should be associated with increased vulnerability to cavitation. Considering the currently proposed models of air-seeding, pit features such as rare, large pores in the pit membrane, torus extensions, and plasmodesmatal pores in a torus can represent potential glitches. These aberrations in pit structure could either result from inherent developmental flaws, or from damage caused to the pit membrane by chemical and physical agents. This suggests the existence of interesting feedbacks between abiotic and biotic stresses in xylem physiology.
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Affiliation(s)
- Lenka Plavcová
- Institute for Systematic Botany and Ecology, Ulm UniversityUlm, Germany
- *Correspondence: Lenka Plavcová, Institute for Systematic Botany and Ecology, Ulm University, Albert-Einstein-Allee 11, D-89081 Ulm, Germany e-mail:
| | - Steven Jansen
- Institute for Systematic Botany and Ecology, Ulm UniversityUlm, Germany
| | - Matthias Klepsch
- Institute for Systematic Botany and Ecology, Ulm UniversityUlm, Germany
| | - Uwe G. Hacke
- Department of Renewable Resources, University of AlbertaEdmonton, AB, Canada
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Zwieniecki MA, Secchi F. Getting variable xylem hydraulic resistance under control: interplay of structure and function. TREE PHYSIOLOGY 2012; 32:1431-1433. [PMID: 23243066 DOI: 10.1093/treephys/tps121] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
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Plavcová L, Hacke UG. Phenotypic and developmental plasticity of xylem in hybrid poplar saplings subjected to experimental drought, nitrogen fertilization, and shading. JOURNAL OF EXPERIMENTAL BOTANY 2012; 63:6481-91. [PMID: 23095999 PMCID: PMC3504499 DOI: 10.1093/jxb/ers303] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Variation in xylem structure and function has been extensively studied across different species with a wide taxonomic, geographical, and ecological coverage. In contrast, our understanding of how xylem of a single species can adjust to different growing condition remains limited. Here phenotypic and developmental plasticity in xylem traits of hybrid poplar (Populus trichocarpa×deltoides) was studied. Clonally propagated saplings were grown under experimental drought, nitrogen fertilization, and shade for >30 d. Xylem hydraulic and anatomical traits were subsequently examined in stem segments taken from two different vertical positions along the plant's main axis. The experimental treatments affected growth and development and induced changes in xylem phenotype. Across all treatments, the amount of leaf area supported by stem segments (A(L)) scaled linearly with stem native hydraulic conductivity (K (native)), suggesting that the area of assimilating leaves is constrained by the xylem transport capacity. In turn, K (native) was mainly driven by the size of xylem cross-sectional area (A(X)). Moreover, the structural and functional properties of xylem varied significantly. Vulnerability to cavitation, measured as the xylem pressure inducing 50% loss of conductivity (P50), ranged from -1.71 MPa to -0.15 MPa in saplings subjected to drought and nitrogen fertilization, respectively. Across all treatments and stem segment positions, P50 was tightly correlated with wood density. In contrast, no relationship between P50 and xylem-specific conductivity (K (S)) was observed. The results of this study enhance our knowledge of plant hydraulic acclimation and provide insights into common trade-offs that exist in xylem structure and function.
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Affiliation(s)
- Lenka Plavcová
- University of Alberta, Department of Renewable Resources, 4-42 Earth Sciences Building, Edmonton, AB, Canada, T6G 2E3.
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Mott KA. Virtual special issue (VSI) on whole-plant water transport. PLANT, CELL & ENVIRONMENT 2012; 35:1879-1880. [PMID: 23043350 DOI: 10.1111/pce.12010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
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Plavcová L, Hacke UG. Heterogeneous distribution of pectin epitopes and calcium in different pit types of four angiosperm species. THE NEW PHYTOLOGIST 2011; 192:885-897. [PMID: 21801182 DOI: 10.1111/j.1469-8137.2011.03842.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Intervessel pits act as safety valves that prevent the spread of xylem embolism. Pectin-calcium crosslinks within the pit membrane have been proposed to affect xylem vulnerability to cavitation. However, as the chemical composition of pit membranes is poorly understood, this hypothesis has not been verified. Using electron microscopy, immunolabeling, an antimonate precipitation technique, and ruthenium red staining, we studied the distribution of selected polysaccharides and calcium in the pit membranes of four angiosperm tree species. We tested whether shifts in xylem vulnerability resulting from perfusion of stems with a calcium chelating agent corresponded with the distribution of pectic homogalacturonans (HG) and/or calcium within interconduit pit membranes. No HG were detected in the main part of intervessel pit membranes, but were consistently found in the marginal membrane region known as the annulus. Calcium colocalized with HG in the annulus. In contrast to intervessel pits, the membrane of vessel-ray pits showed a high pectin content. The presence of two distinct chemical domains, the annulus and the actual pit membrane, can have substantial implications for pit membrane functioning. We propose that the annulus could affect the observed shift in xylem vulnerability after calcium removal by allowing increased pit membrane deflection.
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Affiliation(s)
- Lenka Plavcová
- Department of Renewable Resources, University of Alberta, 442 Earth Sciences Building, Edmonton, AB, Canada, T6G 2E3
| | - Uwe G Hacke
- Department of Renewable Resources, University of Alberta, 442 Earth Sciences Building, Edmonton, AB, Canada, T6G 2E3
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Nardini A, Salleo S, Jansen S. More than just a vulnerable pipeline: xylem physiology in the light of ion-mediated regulation of plant water transport. JOURNAL OF EXPERIMENTAL BOTANY 2011; 62:4701-18. [PMID: 21765173 DOI: 10.1093/jxb/err208] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Major restrictions to the hydraulic conductance of xylem (K(XYL)) in vascular plants have traditionally been attributed to anatomical constraints. More recently, changes in the cationic concentration of xylem sap have been suggested to be responsible for short-term changes in K(XYL) based on data for 35 dicot species, and very few gymnosperms and ferns, indicating that xylem water transport may no longer be considered as an entirely passive process. Recent studies have revealed that this so-called ionic effect: (i) varies from little or no increase to >30%, (ii) is species specific, (iii) changes on a seasonal basis, (iv) depends on the cationic concentration, (v) is enhanced in embolized stems, and (vi) is positively correlated with vessel grouping. Furthermore, the ionic effect has been suggested to play functional roles in planta with respect to: (i) phloem-mediated control of xylem hydraulic properties, (ii) compensation of cavitation-induced loss of hydraulic conductance, with the result of optimizing light and water utilization, and (iii) differential regulation of water delivery to branches exposed to different levels of light. Pits are likely to play a key role in the ionic effect, which has largely been explained as a consequence of the poly-electrolytic nature and hydrogel properties of the pectic matrix of interconduit pit membranes, despite little evidence that pit membrane pectins remain present after cell hydrolysis. More research is needed to address the ionic effect in more species, physico-chemical properties of pit membranes, and how the ionic effect may increase xylem hydraulic conductance 'on demand'.
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Affiliation(s)
- Andrea Nardini
- Dipartimento di Scienze della Vita, Università di Trieste, Via L. Giorgieri 10, Trieste, Italia.
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Almeida-Rodriguez AM, Hacke UG, Laur J. Influence of evaporative demand on aquaporin expression and root hydraulics of hybrid poplar. PLANT, CELL & ENVIRONMENT 2011; 34:1318-31. [PMID: 21477124 DOI: 10.1111/j.1365-3040.2011.02331.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
When light levels and evaporative demand increase, dynamic physiological changes in roots may be required to restore the water balance at the whole plant level. We hypothesized that a dynamic increase in root hydraulic conductance (L(P)) and aquaporin (AQP) expression could moderate the transpiration-induced drop in water potential (Ψ), allowing continued gas exchange in hybrid poplar (Populus trichocarpa × deltoides) saplings. Fifty-six AQPs have been identified in poplar, but little information about their expression patterns in roots is available, especially from a whole-plant water relations perspective. We measured AQP expression and L(P) in plants subjected to different levels of light and evaporative demand. Shaded plants had only one-tenth the root area of plants growing at higher light levels. Shade-grown saplings experiencing a sudden increase in light exhibited a threefold higher L(P) than plants remaining in shade. This dynamic increase in L(P) corresponded with increased transcript abundance of 15 AQPs out of a total of 33 genes simultaneously assessed by quantitative RT-PCR. The tissue-level localization of transcripts of four AQPs was studied with in situ hybridization. Comprehensive expression profiling in conjunction with physiological and morphological measurements is a valuable reference for future studies on AQP function in poplar.
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