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Liu S, Zheng J. Adaptive strategies based on shrub leaf-stem anatomy and their environmental interpretations in the eastern Qaidam Basin. BMC PLANT BIOLOGY 2024; 24:323. [PMID: 38658848 PMCID: PMC11040798 DOI: 10.1186/s12870-024-05026-3] [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: 10/25/2023] [Accepted: 04/15/2024] [Indexed: 04/26/2024]
Abstract
BACKGROUND Water stress seriously affects the survival of plants in natural ecosystems. Plant resistance to water stress relies on adaptive strategies, which are mainly based on plant anatomy with following relevant functions: (1) increase in water uptake and storage; (2) reduction of water loss; and (3) mechanical reinforcement of tissues. We measured 15 leaf-stem anatomical traits of five dominant shrub species from 12 community plots in the eastern Qaidam Basin to explore adaptive strategies based on plant leaf-stem anatomy at species and community levels. and their relationship with environmental stresses were tested. RESULTS Results showed that the combination of leaf-stem anatomical traits formed three types of adaptive strategies with the drought tolerance of leaf and stem taken as two coordinate axes. Three types of water stress were caused by environmental factors in the eastern Qaidam Basin, and the established adaptive strategy triangle could be well explained by these environmental stresses. The interpretation of the strategic triangle was as follows: (1) exploitative plant strategy, in which leaf and stem adopt the hydraulic efficiency strategy and safety strategy, respectively. This strategy is mostly applied to plants in sandy desert (i.e., Nitraria tangutorum, and Artemisia sphaerocephala) which is mainly influenced by drought stress; (2) stable plant strategy, in which both leaf/assimilation branches and stem adopt hydraulic safety strategy. This strategy is mostly applied to plants in salty desert (i.e., Kalidium foliatum and Haloxylon ammodendron) which aridity has little effect on them; and (3) opportunistic plant strategy, in which leaf and stem adopt hydraulic safety strategy and water transport efficiency strategy. This strategy is mostly applied to plants in multiple habitats (i.e., Sympegma regelii) which is mainly affected by coldness stress. CONCLUSION The proposed adaptive strategy system could provide a basis for elucidating the ecological adaptation mechanism of desert woody plants and the scientific management of natural vegetation in the Qinghai-Tibet Plateau.
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Affiliation(s)
- Siyu Liu
- Beijing Key Laboratory of Forest Resource Ecosystem Processes, Beijing Forestry University, Beijing, 100083, China
| | - Jingming Zheng
- Beijing Key Laboratory of Forest Resource Ecosystem Processes, Beijing Forestry University, Beijing, 100083, China.
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2
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Fickle JC, Pratt RB, Jacobsen AL. Xylem structure and hydraulic function in roots and stems of chaparral shrub species from high and low elevation in the Sierra Nevada, California. PHYSIOLOGIA PLANTARUM 2023; 175:e13970. [PMID: 37401910 DOI: 10.1111/ppl.13970] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2023] [Revised: 06/16/2023] [Accepted: 06/25/2023] [Indexed: 07/05/2023]
Abstract
Xylem structure and hydraulics were compared between individuals at lower and upper elevation distribution limits for five chaparral shrub species along a steep transect in the southern Sierra Nevada, California, USA. Higher-elevation plants experienced frequent winter freeze-thaw events and increased precipitation. We hypothesized that environmental differences would lead to xylem trait differences between high and low elevations, but predictions were complicated because both water stress (low elevation) and freeze-thaw events (high elevation) may select for similar traits, such as narrow vessel diameter. We found significant changes in the ratio of stem xylem area to leaf area (Huber value) between elevations, with more xylem area required to support leaves at low elevations. Co-occurring species significantly differed in their xylem traits, suggesting diverse strategies to cope with the highly seasonal environment of this Mediterranean-type climate region. Roots were more hydraulically efficient and more vulnerable to embolism relative to stems, potentially due to roots being buffered from freeze-thaw stress, which allows them to maintain wider diameter vessels. Knowledge of the structure and function of both roots and stems is likely important in understanding whole-plant response to environmental gradients.
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Affiliation(s)
- Jaycie C Fickle
- Department of Biology, California State University, Bakersfield, California, USA
- University of Utah, Salt Lake City, Utah, USA
| | - R Brandon Pratt
- Department of Biology, California State University, Bakersfield, California, USA
| | - Anna L Jacobsen
- Department of Biology, California State University, Bakersfield, California, USA
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3
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Lens F, Gleason SM, Bortolami G, Brodersen C, Delzon S, Jansen S. Functional xylem characteristics associated with drought-induced embolism in angiosperms. THE NEW PHYTOLOGIST 2022; 236:2019-2036. [PMID: 36039697 DOI: 10.1111/nph.18447] [Citation(s) in RCA: 22] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2022] [Accepted: 08/03/2022] [Indexed: 06/15/2023]
Abstract
Hydraulic failure resulting from drought-induced embolism in the xylem of plants is a key determinant of reduced productivity and mortality. Methods to assess this vulnerability are difficult to achieve at scale, leading to alternative metrics and correlations with more easily measured traits. These efforts have led to the longstanding and pervasive assumed mechanistic link between vessel diameter and vulnerability in angiosperms. However, there are at least two problems with this assumption that requires critical re-evaluation: (1) our current understanding of drought-induced embolism does not provide a mechanistic explanation why increased vessel width should lead to greater vulnerability, and (2) the most recent advancements in nanoscale embolism processes suggest that vessel diameter is not a direct driver. Here, we review data from physiological and comparative wood anatomy studies, highlighting the potential anatomical and physicochemical drivers of embolism formation and spread. We then put forward key knowledge gaps, emphasising what is known, unknown and speculation. A meaningful evaluation of the diameter-vulnerability link will require a better mechanistic understanding of the biophysical processes at the nanoscale level that determine embolism formation and spread, which will in turn lead to more accurate predictions of how water transport in plants is affected by drought.
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Affiliation(s)
- Frederic Lens
- Naturalis Biodiversity Center, PO Box 9517, 2300 RA, Leiden, the Netherlands
- Leiden University, Institute of Biology Leiden, Plant Sciences, Sylviusweg 72, 2333 BE, Leiden, the Netherlands
| | - Sean M Gleason
- Water Management and Systems Research Unit, United States Department of Agriculture, Agricultural Research Service, Fort Collins, CO, 80526, USA
| | - Giovanni Bortolami
- Naturalis Biodiversity Center, PO Box 9517, 2300 RA, Leiden, the Netherlands
| | - Craig Brodersen
- School of the Environment, Yale University, New Haven, CT, 06511, USA
| | - Sylvain Delzon
- University of Bordeaux, INRAE, BIOGECO, 33615, Pessac, France
| | - Steven Jansen
- Institute of Systematic Botany and Ecology, Ulm University, Albert-Einstein-Allee 11, D-89081, Ulm, Germany
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4
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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: 10] [Impact Index Per Article: 3.3] [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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5
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Bonetti S, Breitenstein D, Fatichi S, Domec JC, Or D. Persistent decay of fresh xylem hydraulic conductivity varies with pressure gradient and marks plant responses to injury. PLANT, CELL & ENVIRONMENT 2021; 44:371-386. [PMID: 32964494 DOI: 10.1111/pce.13893] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2020] [Revised: 09/02/2020] [Accepted: 09/07/2020] [Indexed: 05/29/2023]
Abstract
Defining plant hydraulic traits is central to the quantification of ecohydrological processes ranging from land-atmosphere interactions, to tree mortality and water-carbon budgets. A key plant trait is the xylem specific hydraulic conductivity (Kx ), that describes the plant's vascular system capacity to transport water. While xylem's vessels and tracheids are dead upon maturity, the xylem is neither inert nor deadwood, various components of the sapwood and surrounding tissue remaining alive and functional. Moreover, the established definition of Kx assumes linear relations between water flux and pressure gradient by tacitly considering the xylem as a "passive conduit". Here, we re-examine this notion of an inert xylem by systematically characterizing xylem flow in several woody plants using Kx measurements under constant and cyclic pressure gradients. Results show a temporal and pressure gradient dependence of Kx . Additionally, microscopic features in "living branches" are irreversibly modified upon drying of the xylem, thus differentiating the macroscopic definition of Kx for living and dead xylem. The findings highlight the picture of the xylem as a complex and delicate conductive system whose hydraulic behaviour transcends a passive gradient-based flow. The study sheds new light on xylem conceptualization, conductivity measurement protocols, in situ long-distance water transport and ecosystem modelling.
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Affiliation(s)
- Sara Bonetti
- Institute for Sustainable Resources, Bartlett School of Environment, Energy and Resources, University College London, London, UK
- Soil and Terrestrial Environmental Physics, Department of Environmental Systems Science, ETH Zürich, Zürich, Switzerland
| | - Daniel Breitenstein
- Soil and Terrestrial Environmental Physics, Department of Environmental Systems Science, ETH Zürich, Zürich, Switzerland
| | - Simone Fatichi
- Institute of Environmental Engineering, ETH Zurich, Zürich, Switzerland
- Department of Civil and Environmental Engineering, National University of Singapore, Singapore
| | - Jean-Christophe Domec
- Bordeaux Sciences Agro, UMR 1391 INRA ISPA, Gradignan Cedex, France
- Nicholas School of the Environment, Duke University, Durham, North Carolina, USA
| | - Dani Or
- Soil and Terrestrial Environmental Physics, Department of Environmental Systems Science, ETH Zürich, Zürich, Switzerland
- Division of Hydrologic Sciences, Desert Research Institute, Reno, Nevada, USA
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6
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Pratt RB, Tobin MF, Jacobsen AL, Traugh CA, De Guzman ME, Hayes CC, Toschi HS, MacKinnon ED, Percolla MI, Clem ME, Smith PT. Starch storage capacity of sapwood is related to dehydration avoidance during drought. AMERICAN JOURNAL OF BOTANY 2021; 108:91-101. [PMID: 33349932 DOI: 10.1002/ajb2.1586] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Accepted: 09/22/2020] [Indexed: 05/26/2023]
Abstract
PREMISE The xylem tissue of plants performs three principal functions: transport of water, support of the plant body, and nutrient storage. Tradeoffs may arise because different structural requirements are associated with different functions or because suites of traits are under selection that relate to resource acquisition, use, and turnover. The structural and functional basis of xylem storage is not well established. We hypothesized that greater starch storage would be associated with greater sapwood parenchyma and reduced fibers, which would compromise resistance to xylem tensions during dehydration. METHODS We measured cavitation resistance, minimum water potential, starch content, and sapwood parenchyma and fiber area in 30 species of southern California chaparral shrubs (evergreen and deciduous). RESULTS We found that species storing greater starch within their xylem tended to avoid dehydration and were less cavitation resistant, and this was supported by phylogenetic independent contrasts. Greater sapwood starch was associated with greater parenchyma area and reduced fiber area. For species without living fibers, the associations with parenchyma were stronger, suggesting that living fibers may expand starch storage capacity while also contributing to the support function of the vascular tissue. Drought-deciduous species were associated with greater dehydration avoidance than evergreens. CONCLUSIONS Evolutionary forces have led to an association between starch storage and dehydration resistance as part of an adaptive suite of traits. We found evidence for a tradeoff between tissue mechanical traits and starch storage; moreover, the evolution of novel strategies, such as starch-storing living fibers, may mitigate the strength of this tradeoff.
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Affiliation(s)
- R Brandon Pratt
- California State University, Bakersfield, Department of Biology, Bakersfield, California, 93311, USA
| | - Michael F Tobin
- University of Houston-Downtown, Department of Natural Sciences, One Main Street, Houston, Texas, 77002, USA
| | - Anna L Jacobsen
- California State University, Bakersfield, Department of Biology, Bakersfield, California, 93311, USA
| | - Courtney A Traugh
- California State University, Bakersfield, Department of Biology, Bakersfield, California, 93311, USA
| | - Mark E De Guzman
- California State University, Bakersfield, Department of Biology, Bakersfield, California, 93311, USA
| | - Christine C Hayes
- California State University, Bakersfield, Department of Biology, Bakersfield, California, 93311, USA
| | - Hayden S Toschi
- California State University, Bakersfield, Department of Biology, Bakersfield, California, 93311, USA
| | - Evan D MacKinnon
- California State University, Bakersfield, Department of Biology, Bakersfield, California, 93311, USA
| | - Marta I Percolla
- California State University, Bakersfield, Department of Biology, Bakersfield, California, 93311, USA
| | - Michael E Clem
- California State University, Bakersfield, Department of Biology, Bakersfield, California, 93311, USA
| | - Paul T Smith
- California State University, Bakersfield, Department of Biology, Bakersfield, California, 93311, USA
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7
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Wang DR, Venturas MD, Mackay DS, Hunsaker DJ, Thorp KR, Gore MA, Pauli D. Use of hydraulic traits for modeling genotype-specific acclimation in cotton under drought. THE NEW PHYTOLOGIST 2020; 228:898-909. [PMID: 32557592 PMCID: PMC7586954 DOI: 10.1111/nph.16751] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/16/2019] [Accepted: 06/07/2020] [Indexed: 06/11/2023]
Abstract
Understanding the genetic and physiological basis of abiotic stress tolerance under field conditions is key to varietal crop improvement in the face of climate variability. Here, we investigate dynamic physiological responses to water stress in silico and their relationships to genotypic variation in hydraulic traits of cotton (Gossypium hirsutum), an economically important species for renewable textile fiber production. In conjunction with an ecophysiological process-based model, heterogeneous data (plant hydraulic traits, spatially-distributed soil texture, soil water content and canopy temperature) were used to examine hydraulic characteristics of cotton, evaluate their consequences on whole plant performance under drought, and explore potential genotype × environment effects. Cotton was found to have R-shaped hydraulic vulnerability curves (VCs), which were consistent under drought stress initiated at flowering. Stem VCs, expressed as percent loss of conductivity, differed across genotypes, whereas root VCs did not. Simulation results demonstrated how plant physiological stress can depend on the interaction between soil properties and irrigation management, which in turn affect genotypic rankings of transpiration in a time-dependent manner. Our study shows how a process-based modeling framework can be used to link genotypic variation in hydraulic traits to differential acclimating behaviors under drought.
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Affiliation(s)
- Diane R. Wang
- Department of GeographyUniversity at BuffaloBuffaloNY14261USA
- Present address:
Department of AgronomyPurdue UniversityWest LafayetteIN47907USA
| | | | - D. Scott Mackay
- Department of GeographyUniversity at BuffaloBuffaloNY14261USA
| | | | - Kelly R. Thorp
- US Arid‐Land Agricultural Research CenterMaricopaAZ37860USA
| | - Michael A. Gore
- Plant Breeding and Genetics SectionSchool of Integrative Plant ScienceCornell UniversityIthacaNY14853USA
| | - Duke Pauli
- School of Plant SciencesUniversity of ArizonaTucsonAZ85721USA
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8
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Pratt RB, Castro V, Fickle JC, Madsen A, Jacobsen AL. Factors controlling drought resistance in grapevine (Vitis vinifera, chardonnay): application of a new microCT method to assess functional embolism resistance. AMERICAN JOURNAL OF BOTANY 2020; 107:618-627. [PMID: 32232845 DOI: 10.1002/ajb2.1450] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Accepted: 01/15/2020] [Indexed: 06/10/2023]
Abstract
PREMISE Quantifying resistance to embolism in woody plants is important for understanding their drought response. Methods to accurately quantify resistance to embolism continue to be debated. METHODS We used a new microCT-based approach that quantifies embolized conduits and also analyzes conductive conduits by using an x-ray-dense, iodine-rich tracer that moves though the vascular system and can easily be observed in microCT images. Many previous microCT studies assumed that all conduits were initially conductive, which may not be the case if there are developing or occluded conduits. We compared microCT results to a standard benchtop dehydration method and a centrifuge method. During dehydration, we measured gas exchange and quantified water potential at mortality. RESULTS Our microCT curves agreed with previously published microCT curves from the same greenhouse-grown cultivar. We found a significant difference in embolism estimates if we assumed that all water-filled conduits were functional rather than only those containing tracer. Embolism estimates from microCT differed from both the benchtop and centrifuge methods. The benchtop and centrifuge methods did not differ from one another. CONCLUSIONS The new microCT method presented here is valuable in sampling species that may contain nonconductive conduits. Disagreement between microCT and two other methods was likely due to differences in the ways they quantify embolism. MicroCT assess the theoretical effect of embolism, whereas benchtop and centrifuge methods directly measure hydraulic conductivity. The theoretical approach does not fully account for the resistances of flow through a complex 3D vascular network.
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Affiliation(s)
- R Brandon Pratt
- Department of Biology, California State University-Bakersfield, Bakersfield, CA, 93311, USA
| | - Viridiana Castro
- Department of Biology, California State University-Bakersfield, Bakersfield, CA, 93311, USA
| | - Jaycie C Fickle
- Department of Biology, California State University-Bakersfield, Bakersfield, CA, 93311, USA
| | - Angela Madsen
- Department of Biology, California State University-Bakersfield, Bakersfield, CA, 93311, USA
| | - Anna L Jacobsen
- Department of Biology, California State University-Bakersfield, Bakersfield, CA, 93311, USA
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9
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Pratt RB, Castro V, Fickle JC, Jacobsen AL. Embolism resistance of different aged stems of a California oak species (Quercus douglasii): optical and microCT methods differ from the benchtop-dehydration standard. TREE PHYSIOLOGY 2020; 40:5-18. [PMID: 31553460 DOI: 10.1093/treephys/tpz092] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2019] [Revised: 07/30/2019] [Accepted: 08/15/2019] [Indexed: 06/10/2023]
Abstract
Vulnerability of xylem to embolism is an important trait related to drought resistance of plants. Methods continue to be developed and debated for measuring embolism. We tested three methods (benchtop dehydration/hydraulic, micro-computed tomography (microCT) and optical) for assessing the vulnerability to embolism of a native California oak species (Quercus douglasii Hook. & Arn.), including an analysis of three different stem ages. All three methods were found to significantly differ in their estimates, with a greater resistance to embolism as follows: microCT > optical > hydraulic. Careful testing was conducted for the hydraulic method to evaluate multiple known potential artifacts, and none was found. One-year-old stems were more resistant than older stems using microCT and optical methods, but not hydraulic methods. Divergence between the microCT and optical methods from the standard hydraulic method was consistent with predictions based on known errors when estimating theoretical losses in hydraulic function in both microCT and optical methods. When the goal of a study is to describe or predict losses in hydraulic conductivity, neither the microCT nor optical methods are reliable for accurately constructing vulnerability curves of stems; nevertheless, these methods may be useful if the goal of a study is to identify embolism events irrespective of hydraulic conductivity or hydraulic function.
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Affiliation(s)
- R Brandon Pratt
- Department of Biology, California State University, Bakersfield, 9001 Stockdale Hwy, Bakersfield, CA
| | - Viridiana Castro
- Department of Biology, California State University, Bakersfield, 9001 Stockdale Hwy, Bakersfield, CA
| | - Jaycie C Fickle
- Department of Biology, California State University, Bakersfield, 9001 Stockdale Hwy, Bakersfield, CA
| | - Anna L Jacobsen
- Department of Biology, California State University, Bakersfield, 9001 Stockdale Hwy, Bakersfield, CA
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10
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Ramirez AR, De Guzman ME, Dawson TE, Ackerly DD. Plant hydraulic traits reveal islands as refugia from worsening drought. CONSERVATION PHYSIOLOGY 2020; 8:coz115. [PMID: 32015878 PMCID: PMC6988607 DOI: 10.1093/conphys/coz115] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Revised: 12/05/2019] [Accepted: 12/31/2019] [Indexed: 05/14/2023]
Abstract
Relatively mesic environments within arid regions may be important conservation targets as 'climate change refugia' for species persistence in the face of worsening drought conditions. Semi-arid southern California and the relatively mesic environments of California's Channel Islands provide a model system for examining drought responses of plants in potential climate change refugia. Most methods for detecting refugia are focused on 'exposure' of organisms to certain abiotic conditions, which fail to assess how local adaptation or acclimation of plant traits (i.e. 'sensitivity') contribute to or offset the benefits of reduced exposure. Here, we use a comparative plant hydraulics approach to characterize the vulnerability of plants to drought, providing a framework for identifying the locations and trait patterns that underlie functioning climate change refugia. Seasonal water relations, xylem hydraulic traits and remotely sensed vegetation indices of matched island and mainland field sites were used to compare the response of native plants from contrasting island and mainland sites to hotter droughts in the early 21st century. Island plants experienced more favorable water relations and resilience to recent drought. However, island plants displayed low plasticity/adaptation of hydraulic traits to local conditions, which indicates that relatively conserved traits of island plants underlie greater hydraulic safety and localized buffering from regional drought conditions. Our results provide an explanation for how California's Channel Islands function as a regional climate refugia during past and current climate change and demonstrate a physiology-based approach for detecting potential climate change refugia in other systems.
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Affiliation(s)
- Aaron R Ramirez
- Department of Integrative Biology, University of California, 3040 Valley Life Sciences Building #3140 Berkeley CA 94720-3200, USA
- Department of Biology & Environmental Studies, Reed College, Portland, 33203 Southeast Woodstock Blvd., Portland, Oregon 97202-8199, USA
- Corresponding author: Department of Biology & Environmental Studies, Reed College, Portland, 33203 Southeast Woodstock Blvd., Portland, Oregon 97202-8199, USA. Tel: +(503) 517-4101.
| | - Mark E De Guzman
- Department of Biology & Environmental Studies, Reed College, Portland, 33203 Southeast Woodstock Blvd., Portland, Oregon 97202-8199, USA
- Department of Botany & Plant Sciences, University of California, Riverside, 900 University Ave., Riverside CA 92521, USA
| | - Todd E Dawson
- Department of Integrative Biology, University of California, 3040 Valley Life Sciences Building #3140 Berkeley CA 94720-3200, USA
- Department of Environmental Science, Policy, and Management, University of California, 130 Mulford Hall #3114, Berkeley, CA 94720-3114, USA
| | - David D Ackerly
- Department of Integrative Biology, University of California, 3040 Valley Life Sciences Building #3140 Berkeley CA 94720-3200, USA
- Department of Environmental Science, Policy, and Management, University of California, 130 Mulford Hall #3114, Berkeley, CA 94720-3114, USA
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11
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Wason JW, Brodersen CR, Huggett BA. The functional implications of tracheary connections across growth rings in four northern hardwood trees. ANNALS OF BOTANY 2019; 124:297-306. [PMID: 31330537 PMCID: PMC6758585 DOI: 10.1093/aob/mcz076] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2019] [Accepted: 05/02/2019] [Indexed: 05/06/2023]
Abstract
BACKGROUND AND AIMS Deciduous angiosperm trees transport xylem sap through trunks and branches in vessels within annual growth rings. Utilizing previous growth rings for sap transport could increase vessel network size and redundancy but may expose new xylem to residual air embolisms in the network. Despite the important role of vessel networks in sap transport and drought resistance, our understanding of cross-ring connections within and between species is limited. METHODS We studied cross-ring connections in four temperate deciduous trees using dye staining and X-ray microcomputed tomography (microCT) to detect xylem connectivity across growth rings and quantify their impact on hydraulic conductivity. KEY RESULTS Acer rubrum and Fraxinus americana had cross-ring connections visible in microCT but only A. rubrum used previous growth rings for axial sap flow. Fagus grandifolia and Quercus rubra, however, did not have cross-ring connections. Accounting for the number of growth rings that function for axial transport improved hydraulic conductivity estimates. CONCLUSIONS These data suggest that the presence of cross-ring connections may help explain aspects of whole-tree xylem sap transport and should be considered for plant hydraulics measurements in these species and others with similar anatomy.
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Affiliation(s)
- Jay W Wason
- School of Forest Resources, University of Maine, Orono, ME, USA
- School of Forestry and Environmental Studies, Yale University, New Haven, CT, USA
- For correspondence. E-mail
| | - Craig R Brodersen
- School of Forestry and Environmental Studies, Yale University, New Haven, CT, USA
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12
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Venturas MD, Pratt RB, Jacobsen AL, Castro V, Fickle JC, Hacke UG. Direct comparison of four methods to construct xylem vulnerability curves: Differences among techniques are linked to vessel network characteristics. PLANT, CELL & ENVIRONMENT 2019; 42:2422-2436. [PMID: 30997689 DOI: 10.1111/pce.13565] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2019] [Revised: 04/12/2019] [Accepted: 04/15/2019] [Indexed: 06/09/2023]
Abstract
During periods of dehydration, water transport through xylem conduits can become blocked by embolism formation. Xylem embolism compromises water supply to leaves and may lead to losses in productivity or plant death. Vulnerability curves (VCs) characterize plant losses in conductivity as xylem pressures decrease. VCs are widely used to characterize and predict plant water use at different levels of water availability. Several methodologies for constructing VCs exist and sometimes produce different results for the same plant material. We directly compared four VC construction methods on stems of black cottonwood (Populus trichocarpa), a model tree species: dehydration, centrifuge, X-ray-computed microtomography (microCT), and optical. MicroCT VC was the most resistant, dehydration and centrifuge VCs were intermediate, and optical VC was the most vulnerable. Differences among VCs were not associated with how cavitation was induced but were related to how losses in conductivity were evaluated: measured hydraulically (dehydration and centrifuge) versus evaluated from visual information (microCT and optical). Understanding how and why methods differ in estimating vulnerability to xylem embolism is important for advancing knowledge in plant ecophysiology, interpreting literature data, and using accurate VCs in water flux models for predicting plant responses to drought.
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Affiliation(s)
- Martin D Venturas
- School of Biological Sciences, University of Utah, Salt Lake City, 84112, Utah, USA
| | - R Brandon Pratt
- Department of Biology, California State University Bakersfield, Bakersfield, 93311, California, USA
| | - Anna L Jacobsen
- Department of Biology, California State University Bakersfield, Bakersfield, 93311, California, USA
| | - Viridiana Castro
- Department of Biology, California State University Bakersfield, Bakersfield, 93311, California, USA
| | - Jaycie C Fickle
- Department of Biology, California State University Bakersfield, Bakersfield, 93311, California, USA
| | - Uwe G Hacke
- Department of Renewable Resources, University of Alberta, Edmonton, Alberta, T6G 2E3, Canada
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13
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Rodriguez-Zaccaro FD, Valdovinos-Ayala J, Percolla MI, Venturas MD, Pratt RB, Jacobsen AL. Wood structure and function change with maturity: Age of the vascular cambium is associated with xylem changes in current-year growth. PLANT, CELL & ENVIRONMENT 2019; 42:1816-1831. [PMID: 30707440 DOI: 10.1111/pce.13528] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2018] [Revised: 01/27/2019] [Accepted: 01/28/2019] [Indexed: 06/09/2023]
Abstract
Xylem vessel structure changes as trees grow and mature. Age- and development-related changes in xylem structure are likely related to changes in hydraulic function. We examined whether hydraulic function, including hydraulic conductivity and vulnerability to water-stress-induced xylem embolism, changed over the course of cambial development in the stems of 17 tree species. We compared current-year growth of young (1-4 years), intermediate (2-7 years), and older (3-10 years) stems occurring in series along branches. Diffuse and ring porous species were examined, but nearly all species produced only diffuse porous xylem in the distal branches that were examined irrespective of their mature xylem porosity type. Vessel diameter and length increased with cambial age. Xylem became both more conductive and more cavitation resistant with cambial age. Ring porous species had longer and wider vessels and xylem that had higher conductivity and was more vulnerable to cavitation; however, these differences between porosity types were not present in young stem samples. Understanding plant hydraulic function and architecture requires the sampling of multiple-aged tissues because plants may vary considerably in their xylem structural and functional traits throughout the plant body, even over relatively short distances and closely aged tissues.
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Affiliation(s)
| | | | - Marta I Percolla
- Department of Biology, California State University, Bakersfield, Bakersfield, California
| | - Martin D Venturas
- Department of Biology, California State University, Bakersfield, Bakersfield, California
- Departamento de Sistemas y Recursos Naturales, Universidad Politécnica de Madrid (UPM), Madrid, Spain
| | - R Brandon Pratt
- Department of Biology, California State University, Bakersfield, Bakersfield, California
| | - Anna L Jacobsen
- Department of Biology, California State University, Bakersfield, Bakersfield, California
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14
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Umebayashi T, Sperry JS, Smith DD, Love DM. 'Pressure fatigue': the influence of sap pressure cycles on cavitation vulnerability in Acer negundo. TREE PHYSIOLOGY 2019; 39:740-746. [PMID: 30799506 DOI: 10.1093/treephys/tpy148] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Revised: 12/13/2018] [Accepted: 12/19/2018] [Indexed: 05/11/2023]
Abstract
Vulnerability-to-cavitation curves (VCs) can vary within a tree crown in relation to position or branch age. We tested the hypothesis that VC variation can arise from differential susceptibility to the number of diurnal sap pressure cycles experienced. We designed a method to distinguish between effects of cycling vs exposure time to negative pressure, and tested the influence of sap pressure cycles on cavitation vulnerability between upper and lower branches in Acer negundo L. trees using static and flow centrifuge, and air-injection methods. Branches from the upper crown had greater hydraulic conductivity and were more resistant to cavitation than branches from the lower crown. Upper branches also showed little change after exposure to 10 or 20 pressure cycles between -0.5 MPa and -2.0 MPa. Lower branches, however, showed a marked increase in vulnerability to cavitation after pressure-cycling. This result suggests that 'cavitation fatigue' can occur without the actual induction (and reversal) of cavitation as documented previously, but simply from the cycling of pressures in the sub-cavitation range. This 'pressure fatigue' may explain age-related shifts in VCs that could eventually induce dieback in suppressed branches or trees. Pressure fatigue may help explain developmental variation in hydraulic capacity of branches within individuals.
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Affiliation(s)
- Toshihiro Umebayashi
- School of Biological Sciences, University of Utah, 257 S 1400E, Salt Lake City, UT, USA
| | - John S Sperry
- School of Biological Sciences, University of Utah, 257 S 1400E, Salt Lake City, UT, USA
| | - Duncan D Smith
- School of Biological Sciences, University of Utah, 257 S 1400E, Salt Lake City, UT, USA
| | - David M Love
- School of Biological Sciences, University of Utah, 257 S 1400E, Salt Lake City, UT, USA
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15
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Brodersen CR, Roddy AB, Wason JW, McElrone AJ. Functional Status of Xylem Through Time. ANNUAL REVIEW OF PLANT BIOLOGY 2019; 70:407-433. [PMID: 30822114 DOI: 10.1146/annurev-arplant-050718-100455] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Water transport in vascular plants represents a critical component of terrestrial water cycles and supplies the water needed for the exchange of CO2 in the atmosphere for photosynthesis. Yet, many fundamental principles of water transport are difficult to assess given the scale and location of plant xylem. Here we review the mechanistic principles that underpin long-distance water transport in vascular plants, with a focus on woody species. We also discuss the recent development of noninvasive tools to study the functional status of xylem networks in planta. Limitations of current methods to detect drought-induced xylem blockages (e.g., embolisms) and quantify corresponding declines in sap flow, and the coordination of hydraulic dysfunction with other physiological processes are assessed. Future avenues of research focused on cross-validation of plant hydraulics methods are discussed, as well as a proposed fundamental shift in the theory and methodology used to characterize and measure plant water use.
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Affiliation(s)
- Craig R Brodersen
- School of Forestry and Environmental Studies, Yale University, New Haven, Connecticut 06511, USA;
| | - Adam B Roddy
- School of Forestry and Environmental Studies, Yale University, New Haven, Connecticut 06511, USA;
| | - Jay W Wason
- School of Forest Resources, University of Maine, Orono, Maine 04469, USA
| | - Andrew J McElrone
- US Department of Agriculture, Agricultural Research Service, Davis, California 95616, USA
- Department of Viticulture and Enology, University of California, Davis, California 95616, USA
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16
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López R, Nolf M, Duursma RA, Badel E, Flavel RJ, Cochard H, Choat B. Mitigating the open vessel artefact in centrifuge-based measurement of embolism resistance. TREE PHYSIOLOGY 2019; 39:143-155. [PMID: 30085232 DOI: 10.1093/treephys/tpy083] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Accepted: 07/03/2018] [Indexed: 06/08/2023]
Abstract
Centrifuge-based techniques to assess xylem vulnerability to embolism are increasingly being used, although we are yet to reach a consensus on the nature and extent of artefactual embolism observed in some angiosperm species. In particular, there is disagreement over whether these artefacts influence both the spin (Cavitron) and static versions of the centrifuge technique equally. We tested two methods for inducing embolism: bench dehydration and centrifugation. We used three methods to measure the resulting loss of conductivity: gravimetric flow measured in bench-dehydrated and centrifuged samples (static centrifuge), in situ flow measured under tension during spinning in the centrifuge (Cavitron) and direct imaging using X-ray computed microtomography (microCT) observations in stems of two species of Hakea that differ in vessel length. Both centrifuge techniques were prone to artefactual embolism in samples with maximum vessel length longer than, or similar to, the centrifuge rotor diameter. Observations with microCT indicated that this artefactual embolism occurred in the outermost portions of samples. The artefact was largely eliminated if flow was measured in an excised central part of the segment in the static centrifuge or starting measurements with the Cavitron at pressures lower than the threshold of embolism formation in open vessels. The simulations of loss of conductivity in centrifuged samples with a new model, CAVITOPEN, confirmed that the impact of open vessels on the vulnerability to embolism curve was higher when vessels were long, samples short and when embolism is formed in open vessels at less negative pressures. This model also offers a robust and quantitative tool to test and correct for artefactual embolism at low xylem tensions.
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Affiliation(s)
- Rosana López
- Université Clermont Auvergne, INRA, PIAF, 5, chemin de Beaulieu, Clermont-Ferrand, France
- Sistemas y Recursos Naturales, Universidad Politécnica de Madrid, C/ José Antonio Novais 10, Madrid, Spain
| | - Markus Nolf
- Hawkesbury Institute for the Environment, Western Sydney University, Hawkesbury Campus, Locked Bag 1797, Penrith, NSW, Australia
| | - Remko A Duursma
- Hawkesbury Institute for the Environment, Western Sydney University, Hawkesbury Campus, Locked Bag 1797, Penrith, NSW, Australia
| | - Eric Badel
- Université Clermont Auvergne, INRA, PIAF, 5, chemin de Beaulieu, Clermont-Ferrand, France
| | - Richard J Flavel
- School of Environmental and Rural Science, University of New England, Elm Avenue, 2351 Armidale, NSW, Australia
| | - Hervé Cochard
- Université Clermont Auvergne, INRA, PIAF, 5, chemin de Beaulieu, Clermont-Ferrand, France
| | - Brendan Choat
- Hawkesbury Institute for the Environment, Western Sydney University, Hawkesbury Campus, Locked Bag 1797, Penrith, NSW, Australia
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17
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De Guzman ME, Santiago LS, Schnitzer SA, Álvarez-Cansino L. Trade-offs between water transport capacity and drought resistance in neotropical canopy liana and tree species. TREE PHYSIOLOGY 2017; 37:1404-1414. [PMID: 27672189 DOI: 10.1093/treephys/tpw086] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Accepted: 08/04/2016] [Indexed: 06/06/2023]
Abstract
In tropical forest canopies, it is critical for upper shoots to efficiently provide water to leaves for physiological function while safely preventing loss of hydraulic conductivity due to cavitation during periods of soil water deficit or high evaporative demand. We compared hydraulic physiology of upper canopy trees and lianas in a seasonally dry tropical forest to test whether trade-offs between safety and efficiency of water transport shape differences in hydraulic function between these two major tropical woody growth forms. We found that lianas showed greater maximum stem-specific hydraulic conductivity than trees, but lost hydraulic conductivity at less negative water potentials than trees, resulting in a negative correlation and trade-off between safety and efficiency of water transport. Lianas also exhibited greater diurnal changes in leaf water potential than trees. The magnitude of diurnal water potential change was negatively correlated with sapwood capacitance, indicating that lianas are highly reliant on conducting capability to maintain leaf water status, whereas trees relied more on stored water in stems to maintain leaf water status. Leaf nitrogen concentration was related to maximum leaf-specific hydraulic conductivity only for lianas suggesting that greater water transport capacity is more tied to leaf processes in lianas compared to trees. Our results are consistent with a trade-off between safety and efficiency of water transport and may have implications for increasing liana abundance in neotropical forests.
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Affiliation(s)
- Mark E De Guzman
- Department of Botany & Plant Sciences, University of California, Riverside, CA 92521, USA
| | - Louis S Santiago
- Department of Botany & Plant Sciences, University of California, Riverside, CA 92521, USA
- Smithsonian Tropical Research Institute, Apartado 0843-0392, Balboa, Panamá
| | - Stefan A Schnitzer
- Smithsonian Tropical Research Institute, Apartado 0843-0392, Balboa, Panamá
- Department of Biological Sciences, Marquette University, Milwaukee, WI 53201, USA
| | - Leonor Álvarez-Cansino
- Smithsonian Tropical Research Institute, Apartado 0843-0392, Balboa, Panamá
- Department of Plant Ecology, University of Bayreuth, Universitätsstrasse 30, 95440 Bayreuth, Germany
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18
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Torres-Ruiz JM, Cochard H, Choat B, Jansen S, López R, Tomášková I, Padilla-Díaz CM, Badel E, Burlett R, King A, Lenoir N, Martin-StPaul NK, Delzon S. Xylem resistance to embolism: presenting a simple diagnostic test for the open vessel artefact. THE NEW PHYTOLOGIST 2017; 215:489-499. [PMID: 28467616 DOI: 10.1111/nph.14589] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/02/2017] [Accepted: 03/28/2017] [Indexed: 05/21/2023]
Abstract
Xylem vulnerability to embolism represents an essential trait for the evaluation of the impact of hydraulics in plant function and ecology. The standard centrifuge technique is widely used for the construction of vulnerability curves, although its accuracy when applied to species with long vessels remains under debate. We developed a simple diagnostic test to determine whether the open-vessel artefact influences centrifuge estimates of embolism resistance. Xylem samples from three species with differing vessel lengths were exposed to less negative xylem pressures via centrifugation than the minimum pressure the sample had previously experienced. Additional calibration was obtained from non-invasive measurement of embolism on intact olive plants by X-ray microtomography. Results showed artefactual decreases in hydraulic conductance (k) for samples with open vessels when exposed to a less negative xylem pressure than the minimum pressure they had previously experienced. X-Ray microtomography indicated that most of the embolism formation in olive occurs at xylem pressures below -4.0 MPa, reaching 50% loss of hydraulic conductivity at -5.3 MPa. The artefactual reductions in k induced by centrifugation underestimate embolism resistance data of species with long vessels. A simple test is suggested to avoid this open vessel artefact and to ensure the reliability of this technique in future studies.
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Affiliation(s)
| | - Hervé Cochard
- PIAF, INRA, University of Clermont-Auvergne, 63100, Clermont-Ferrand, France
| | - Brendan Choat
- Western Sydney University, Hawkesbury Institute for the Environment, Richmond, NSW, 2753, Australia
| | - Steven Jansen
- Ulm University, Institute of Systematic Botany and Ecology, Albert-Einstein-Allee 11, 89081, Ulm, Germany
| | - Rosana López
- PIAF, INRA, University of Clermont-Auvergne, 63100, Clermont-Ferrand, France
- Western Sydney University, Hawkesbury Institute for the Environment, Richmond, NSW, 2753, Australia
| | - Ivana Tomášková
- Faculty of Forestry and Wood Sciences, Czech University of Life Sciences, Kamýcká 129, 165 00, Praha 6 - Suchdol, Czech Republic
| | - Carmen M Padilla-Díaz
- Instituto de Recursos Naturales y Agrobiología de Sevilla (IRNAS, CSIC), Avenida Reina Mercedes, 10, 41012, Sevilla, Spain
| | - Eric Badel
- PIAF, INRA, University of Clermont-Auvergne, 63100, Clermont-Ferrand, France
| | - Regis Burlett
- BIOGECO, INRA, University of Bordeaux, 33615, Pessac, France
| | - Andrew King
- Synchrotron SOLEIL, L'Orme de Merisiers, 91190 Saint-Aubin - BP48, Gif-sur-Yvette Cedex, France
| | - Nicolas Lenoir
- CNRS, University of Bordeaux, UMS 3626 Placamat, F-33608, Pessac, France
| | | | - Sylvain Delzon
- BIOGECO, INRA, University of Bordeaux, 33615, Pessac, France
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19
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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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20
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Wolfe BT, Sperry JS, Kursar TA. Does leaf shedding protect stems from cavitation during seasonal droughts? A test of the hydraulic fuse hypothesis. THE NEW PHYTOLOGIST 2016; 212:1007-1018. [PMID: 27373446 DOI: 10.1111/nph.14087] [Citation(s) in RCA: 85] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2016] [Accepted: 06/01/2016] [Indexed: 05/04/2023]
Abstract
During droughts, leaves are predicted to act as 'hydraulic fuses' by shedding when plants reach critically low water potential (Ψplant ), thereby slowing water loss, stabilizing Ψplant and protecting against cavitation-induced loss of stem hydraulic conductivity (Ks ). We tested these predictions among trees in seasonally dry tropical forests, where leaf shedding is common, yet variable, among species. We tracked leaf phenology, Ψplant and Ks in saplings of six tree species distributed across two forests. Species differed in their timing and extent of leaf shedding, yet converged in shedding leaves as they approached the Ψplant value associated with a 50% loss of Ks and at which their model-estimated maximum sustainable transpiration rate approached zero. However, after shedding all leaves, the Ψplant value of one species, Genipa americana, continued to decline, indicating that water loss continued after leaf shedding. Ks was highly variable among saplings within species and seasons, suggesting a minimal influence of seasonal drought on Ks . Hydraulic limits appear to drive diverse patterns of leaf shedding among tropical trees, supporting the hydraulic fuse hypothesis. However, leaf shedding is not universally effective at stabilizing Ψplant , suggesting that the main function of drought deciduousness may vary among species.
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Affiliation(s)
- Brett T Wolfe
- Department of Biology, University of Utah, Salt Lake City, UT, 84112, USA
- Smithsonian Tropical Research Institute, PO Box 0843-03092, Balboa, Ancon, Panama
| | - John S Sperry
- Department of Biology, University of Utah, Salt Lake City, UT, 84112, USA
| | - Thomas A Kursar
- Department of Biology, University of Utah, Salt Lake City, UT, 84112, USA
- Smithsonian Tropical Research Institute, PO Box 0843-03092, Balboa, Ancon, Panama
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21
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Jacobsen AL, Tobin MF, Toschi HS, Percolla MI, Pratt RB. Structural determinants of increased susceptibility to dehydration-induced cavitation in post-fire resprouting chaparral shrubs. PLANT, CELL & ENVIRONMENT 2016; 39:2473-2485. [PMID: 27423060 DOI: 10.1111/pce.12802] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Revised: 07/06/2016] [Accepted: 07/11/2016] [Indexed: 06/06/2023]
Abstract
It is well established that transpiration and photosynthetic rates generally increase in resprouting shoots after fire in chaparral shrublands. By contrast, little is known about how plant hydraulic function varies during this same recovery period. We hypothesized that vascular traits, both functional and structural, would also shift in order to support this heightened level of gas exchange and growth. We examined stem xylem-specific hydraulic conductivity (Ks ) and resistance to cavitation (P50 ) for eight chaparral shrub species as well as several potential xylem structural determinants of hydraulic function and compared established unburned plants and co-occurring post-fire resprouting plants. Unburned plants were generally more resistant to cavitation than resprouting plants, but the two groups did not differ in Ks . Resprouting plants had altered vessel structure compared with unburned plants, with resprouting plants having both wider diameter vessels and higher inter-vessel pit density. For biomechanics, unburned plants had both stronger and denser stem xylem tissue than resprouting plants. Shifts in hydraulic structure and function resulted in resprouting plants being more vulnerable to dehydration. The interaction between time since disturbance (i.e. resprouting versus established stands) and drought may complicate attempts to predict mortality risk of resprouting plants.
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Affiliation(s)
- Anna L Jacobsen
- Department of Biology, California State University, Bakersfield, 9001 Stockdale Highway, Bakersfield, CA, 93311, USA.
| | - Michael F Tobin
- Department of Natural Sciences, University of Houston-Downtown, One Main Street, Houston, TX, 77002, USA
| | - Hayden S Toschi
- Department of Biology, California State University, Bakersfield, 9001 Stockdale Highway, Bakersfield, CA, 93311, USA
| | - Marta I Percolla
- Department of Biology, California State University, Bakersfield, 9001 Stockdale Highway, Bakersfield, CA, 93311, USA
| | - R Brandon Pratt
- Department of Biology, California State University, Bakersfield, 9001 Stockdale Highway, Bakersfield, CA, 93311, USA
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22
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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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23
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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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24
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Fukuda K, Kawaguchi D, Aihara T, Ogasa MY, Miki NH, Haishi T, Umebayashi T. Vulnerability to cavitation differs between current-year and older xylem: non-destructive observation with a compact magnetic resonance imaging system of two deciduous diffuse-porous species. PLANT, CELL & ENVIRONMENT 2015; 38:2508-18. [PMID: 25630712 DOI: 10.1111/pce.12510] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2014] [Revised: 12/30/2014] [Accepted: 01/09/2015] [Indexed: 05/26/2023]
Abstract
Development of xylem embolism during water stress in two diffuse-porous hardwoods, Katsura (Cercidiphyllum japonicum) and Japanese white birch (Betula platyphylla var. japonica), was observed non-destructively under a compact magnetic resonance imaging (MRI) system in addition to conventional quantitation of hydraulic vulnerability to cavitation from excised stem segments. Distribution of white and dark areas in MR images corresponded well to the distribution of water-filled/embolized vessels observed by cryo-scanning electron microscopy in both species. Water-filled vessels were observed in MR images as white areas in Katsura and as white dots in Japanese white birch, respectively, and embolisms could be detected as a change to dark areas. The increase in the relative embolized area (REA: %) in the cross-sectional area of total xylem during water stress, which was estimated from the binarized MR images, was consistent with the hydraulic vulnerability curves of these species. From the non-destructive MRI observations, cavitation induced by water stress was shown to develop earlier in 1- or 2-year-old xylem than in the current-year xylem in both species; that is, the vulnerability to cavitation differs between vessels in the current-year xylem and those in older annual rings.
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Affiliation(s)
- Kenji Fukuda
- Department of Natural Environmental Studies, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, 277-8563, Japan
| | - Daichi Kawaguchi
- Department of Natural Environmental Studies, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, 277-8563, Japan
| | - Tomo Aihara
- Graduate School of Environmental and Life Science, Okayama University, Okayama, 700-8530, Japan
| | - Mayumi Y Ogasa
- Department of Natural Environmental Studies, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, 277-8563, Japan
| | - Naoko H Miki
- Graduate School of Environmental and Life Science, Okayama University, Okayama, 700-8530, Japan
| | | | - Toshihiro Umebayashi
- Department of Natural Environmental Studies, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, 277-8563, Japan
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25
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Rosner S. A new type of vulnerability curve: is there truth in vine? TREE PHYSIOLOGY 2015; 35:410-4. [PMID: 25240728 DOI: 10.1093/treephys/tpu080] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2014] [Accepted: 08/17/2014] [Indexed: 05/23/2023]
Affiliation(s)
- Sabine Rosner
- Institute of Botany, BOKU Vienna, Gregor Mendel Str. 33, A-1180 Vienna, Austria
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26
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Pratt RB, MacKinnon ED, Venturas MD, Crous CJ, Jacobsen AL. Root resistance to cavitation is accurately measured using a centrifuge technique. TREE PHYSIOLOGY 2015; 35:185-196. [PMID: 25716876 DOI: 10.1093/treephys/tpv003] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Plants transport water under negative pressure and this makes their xylem vulnerable to cavitation. Among plant organs, root xylem is often highly vulnerable to cavitation due to water stress. The use of centrifuge methods to study organs, such as roots, that have long vessels are hypothesized to produce erroneous estimates of cavitation resistance due to the presence of open vessels through measured samples. The assumption that roots have long vessels may be premature since data for root vessel length are sparse; moreover, recent studies have not supported the existence of a long-vessel artifact for stems when a standard centrifuge technique was used. We examined resistance to cavitation estimated using a standard centrifuge technique and compared these values with native embolism measurements for roots of seven woody species grown in a common garden. For one species we also measured vulnerability using single-vessel air injection. We found excellent agreement between root native embolism and the levels of embolism measured using a centrifuge technique, and with air-seeding estimates from single-vessel injection. Estimates of cavitation resistance measured from centrifuge curves were biologically meaningful and were correlated with field minimum water potentials, vessel diameter (VD), maximum xylem-specific conductivity (Ksmax) and vessel length. Roots did not have unusually long vessels compared with stems; moreover, root vessel length was not correlated to VD or to the vessel length of stems. These results suggest that root cavitation resistance can be accurately and efficiently measured using a standard centrifuge method and that roots are highly vulnerable to cavitation. The role of root cavitation resistance in determining drought tolerance of woody species deserves further study, particularly in the context of climate change.
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Affiliation(s)
- R B Pratt
- Department of Biology, California State University, Bakersfield, 9001 Stockdale Hwy, Bakersfield, CA 93311, USA
| | - E D MacKinnon
- Department of Biology, California State University, Bakersfield, 9001 Stockdale Hwy, Bakersfield, CA 93311, USA
| | - M D Venturas
- Department of Biology, California State University, Bakersfield, 9001 Stockdale Hwy, Bakersfield, CA 93311, USA
| | - C J Crous
- Forestry and Agricultural Biotechnology Institute, University of Pretoria, Pretoria 0002, South Africa
| | - A L Jacobsen
- Department of Biology, California State University, Bakersfield, 9001 Stockdale Hwy, Bakersfield, CA 93311, USA
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27
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Hacke UG, Venturas MD, MacKinnon ED, Jacobsen AL, Sperry JS, Pratt RB. The standard centrifuge method accurately measures vulnerability curves of long-vesselled olive stems. THE NEW PHYTOLOGIST 2015; 205:116-27. [PMID: 25229841 DOI: 10.1111/nph.13017] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2014] [Accepted: 08/01/2014] [Indexed: 05/02/2023]
Abstract
The standard centrifuge method has been frequently used to measure vulnerability to xylem cavitation. This method has recently been questioned. It was hypothesized that open vessels lead to exponential vulnerability curves, which were thought to be indicative of measurement artifact. We tested this hypothesis in stems of olive (Olea europea) because its long vessels were recently claimed to produce a centrifuge artifact. We evaluated three predictions that followed from the open vessel artifact hypothesis: shorter stems, with more open vessels, would be more vulnerable than longer stems; standard centrifuge-based curves would be more vulnerable than dehydration-based curves; and open vessels would cause an exponential shape of centrifuge-based curves. Experimental evidence did not support these predictions. Centrifuge curves did not vary when the proportion of open vessels was altered. Centrifuge and dehydration curves were similar. At highly negative xylem pressure, centrifuge-based curves slightly overestimated vulnerability compared to the dehydration curve. This divergence was eliminated by centrifuging each stem only once. The standard centrifuge method produced accurate curves of samples containing open vessels, supporting the validity of this technique and confirming its utility in understanding plant hydraulics. Seven recommendations for avoiding artefacts and standardizing vulnerability curve methodology are provided.
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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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28
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Cochard H, Delzon S, Badel E. X-ray microtomography (micro-CT): a reference technology for high-resolution quantification of xylem embolism in trees. PLANT, CELL & ENVIRONMENT 2015; 38:201-6. [PMID: 24942003 DOI: 10.1111/pce.12391] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2014] [Revised: 06/10/2014] [Accepted: 06/15/2014] [Indexed: 05/02/2023]
Abstract
As current methods for measuring xylem embolism in trees are indirect and prone to artefacts, there is an ongoing controversy over the capacity of trees to resist or recover from embolism. The debate will not end until we get direct visualization of the vessel content. Here, we propose desktop X-ray microtomography (micro-CT) as a reference direct technique to quantify xylem embolism and thus validate more widespread measurements based upon either hydraulic or acoustic methods. We used desktop micro-CT to measure embolism levels in dehydrated or centrifuged shoots of laurel - a long-vesseled species thought to display daily cycles of embolism formation and refilling. Our direct observations demonstrate that this Mediterranean species is highly resistant to embolism and is not vulnerable to drought-induced embolism in a normal range of xylem tensions. We therefore recommend that embolism studies in long-vesseled species should be validated by direct methods such as micro-CT to clear up any misunderstandings on their physiology.
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Affiliation(s)
- H Cochard
- UMR 547 PIAF, INRA, 63100, Clermont-Ferrand, France; UMR 547 PIAF, Clermont Université, Université Blaise-Pascal, 63000, Clermont-Ferrand, France
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29
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Torres-Ruiz JM, Cochard H, Mayr S, Beikircher B, Diaz-Espejo A, Rodriguez-Dominguez CM, Badel E, Fernández JE. Vulnerability to cavitation in Olea europaea current-year shoots: further evidence of an open-vessel artifact associated with centrifuge and air-injection techniques. PHYSIOLOGIA PLANTARUM 2014; 152:465-74. [PMID: 24611594 DOI: 10.1111/ppl.12185] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2013] [Revised: 02/20/2014] [Accepted: 02/25/2014] [Indexed: 05/02/2023]
Abstract
Different methods have been devised to analyze vulnerability to cavitation of plants. Although a good agreement between them is usually found, some discrepancies have been reported when measuring samples from long-vesseled species. The aim of this study was to evaluate possible artifacts derived from different methods and sample sizes. Current-year shoot segments of mature olive trees (Olea europaea), a long-vesseled species, were used to generate vulnerability curves (VCs) by bench dehydration, pressure collar and both static- and flow-centrifuge methods. For the latter, two different rotors were used to test possible effects of the rotor design on the curves. Indeed, high-resolution computed tomography (HRCT) images were used to evaluate the functional status of xylem at different water potentials. Measurements of native embolism were used to validate the methods used. The pressure collar and the two centrifugal methods showed greater vulnerability to cavitation than the dehydration method. The shift in vulnerability thresholds in centrifuge methods was more pronounced in shorter samples, supporting the open-vessel artifact hypothesis as a higher proportion of vessels were open in short samples. The two different rotor designs used for the flow-centrifuge method revealed similar vulnerability to cavitation. Only the bench dehydration or HRCT methods produced VCs that agreed with native levels of embolism and water potential values measured in the field.
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Affiliation(s)
- José M Torres-Ruiz
- Irrigation and Crop Ecophysiology Group, Instituto de Recursos Naturales y Agrobiología de Sevilla (IRNAS, CSIC), Avenida Reina Mercedes, No. 10, Sevilla, 41012, Spain
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30
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Jacobsen AL, Pratt RB, Davis SD, Tobin MF. Geographic And Seasonal Variation In Chaparral Vulnerability To Cavitation. ACTA ACUST UNITED AC 2014. [DOI: 10.3120/0024-9637-61.4.317] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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31
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Martin-StPaul NK, Longepierre D, Huc R, Delzon S, Burlett R, Joffre R, Rambal S, Cochard H. How reliable are methods to assess xylem vulnerability to cavitation? The issue of 'open vessel' artifact in oaks. TREE PHYSIOLOGY 2014; 34:894-905. [PMID: 25074860 DOI: 10.1093/treephys/tpu059] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Three methods are in widespread use to build vulnerability curves (VCs) to cavitation. The bench drying (BD) method is considered as a reference because embolism and xylem pressure are measured on large branches dehydrating in the air, in conditions similar to what happens in nature. Two other methods of embolism induction have been increasingly used. While the Cavitron (CA) uses centrifugal force to induce embolism, in the air injection (AI) method embolism is induced by forcing pressurized air to enter a stem segment. Recent studies have suggested that the AI and CA methods are inappropriate in long-vesselled species because they produce a very high-threshold xylem pressure for embolism (e.g., P50) compared with what is expected from (i) their ecophysiology in the field (native embolism, water potential and stomatal response to xylem pressure) and (ii) the P50 obtained with the BD method. However, other authors have argued that the CA and AI methods may be valid because they produce VCs similar to the BD method. In order to clarify this issue, we assessed VCs with the three above-mentioned methods on the long-vesselled Quercus ilex L. We showed that the BD VC yielded threshold xylem pressure for embolism consistent with in situ measurements of native embolism, minimal water potential and stomatal conductance. We therefore concluded that the BD method provides a reliable estimate of the VC for this species. The CA method produced a very high P50 (i.e., less negative) compared with the BD method, which is consistent with an artifact related to the vessel length. The VCs obtained with the AI method were highly variable, producing P50 ranging from -2 to -8.2 MPa. This wide variability was more related to differences in base diameter among samples than to differences in the length of samples. We concluded that this method is probably subject to an artifact linked to the distribution of vessel lengths within the sample. Overall, our results indicate that the CA and the AI should be used with extreme caution on long-vesselled species. Our results also highlight that several criteria may be helpful to assess the validity of a VC.
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Affiliation(s)
- N K Martin-StPaul
- CEFE UMR 5175, CNRS-Université de Montpellier-Université Paul-Valéry Montpellier-EPHE-IRD, 1919 route de Mende 34293 Montpellier Cedex 5, France Laboratoire Ecologie Systématique et Evolution CNRS, Orsay F-91405, France
| | - D Longepierre
- CEFE UMR 5175, CNRS-Université de Montpellier-Université Paul-Valéry Montpellier-EPHE-IRD, 1919 route de Mende 34293 Montpellier Cedex 5, France
| | - R Huc
- INRA UR629, Ecologie des Forêts Méditerranéennes (URFM), Domaine Saint Paul Site Agroparc, 84194 Avignon Cedex 9, France
| | - S Delzon
- INRA, UMR 1202 BIOGECO, F-33610 Cestas, France Université de Bordeaux, UMR 1202 BIOGECO, F-33610 Cestas, France
| | - R Burlett
- INRA, UMR 1202 BIOGECO, F-33610 Cestas, France Université de Bordeaux, UMR 1202 BIOGECO, F-33610 Cestas, France
| | - R Joffre
- CEFE UMR 5175, CNRS-Université de Montpellier-Université Paul-Valéry Montpellier-EPHE-IRD, 1919 route de Mende 34293 Montpellier Cedex 5, France
| | - S Rambal
- CEFE UMR 5175, CNRS-Université de Montpellier-Université Paul-Valéry Montpellier-EPHE-IRD, 1919 route de Mende 34293 Montpellier Cedex 5, France Universidade Federal de Lavras, Departamento de Biologia, CP 3037, CEP 37200-000, Lavras, MG, Brazil
| | - H Cochard
- INRA, UMR 547 PIAF, F-63100 Clermont-Ferrand, France Université Blaise Pascal, UMR 547 PIAF, F-63177 Aubière, France
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32
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Pivovaroff AL, Sack L, Santiago LS. Coordination of stem and leaf hydraulic conductance in southern California shrubs: a test of the hydraulic segmentation hypothesis. THE NEW PHYTOLOGIST 2014; 203:842-50. [PMID: 24860955 DOI: 10.1111/nph.12850] [Citation(s) in RCA: 96] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2014] [Accepted: 04/16/2014] [Indexed: 05/05/2023]
Abstract
Coordination of water movement among plant organs is important for understanding plant water use strategies. The hydraulic segmentation hypothesis (HSH) proposes that hydraulic conductance in shorter lived, 'expendable' organs such as leaves and longer lived, more 'expensive' organs such as stems may be decoupled, with resistance in leaves acting as a bottleneck or 'safety valve'. We tested the HSH in woody species from a Mediterranean-type ecosystem by measuring leaf hydraulic conductance (Kleaf) and stem hydraulic conductivity (KS). We also investigated whether leaves function as safety valves by relating Kleaf and the hydraulic safety margin (stem water potential minus the water potential at which 50% of conductivity is lost (Ψstem-Ψ50)). We also examined related plant traits including the operating range of water potentials, wood density, leaf mass per area, and leaf area to sapwood area ratio to provide insight into whole-plant water use strategies. For hydrated shoots, Kleaf was negatively correlated with KS , supporting the HSH. Additionally, Kleaf was positively correlated with the hydraulic safety margin and negatively correlated with the leaf area to sapwood area ratio. Consistent with the HSH, our data indicate that leaves may act as control valves for species with high KS , or a low safety margin. This critical role of leaves appears to contribute importantly to plant ecological specialization in a drought-prone environment.
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Affiliation(s)
- Alexandria L Pivovaroff
- Department of Botany and Plant Sciences, University of California, 2150 Batchelor Hall, Riverside, CA, 92521, USA
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33
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Delzon S, Cochard H. Recent advances in tree hydraulics highlight the ecological significance of the hydraulic safety margin. THE NEW PHYTOLOGIST 2014; 203:355-358. [PMID: 24661229 DOI: 10.1111/nph.12798] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Affiliation(s)
- Sylvain Delzon
- INRA, University of Bordeaux, UMR BIOGECO, F-33450, Talence, France
| | - Hervé Cochard
- INRA, Clermont University, UMR547 PIAF, F-63100, Clermont-Ferrand, France
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34
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Pratt RB, Jacobsen AL, Ramirez AR, Helms AM, Traugh CA, Tobin MF, Heffner MS, Davis SD. Mortality of resprouting chaparral shrubs after a fire and during a record drought: physiological mechanisms and demographic consequences. GLOBAL CHANGE BIOLOGY 2014; 20:893-907. [PMID: 24375846 DOI: 10.1111/gcb.12477] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2013] [Accepted: 10/24/2013] [Indexed: 06/03/2023]
Abstract
We examined postfire regeneration of chaparral shrubs during an intense drought. This study focused on the demography and physiology of shrub species that resprout from a basal lignotuber following fire. We found significant levels of resprout mortality when intense drought occurred in the year following fire during the period of shrub recovery. Three of the seven sampled resprouting species had the greatest or near greatest levels of mortality ever recorded when compared to previous studies. Most shrub mortality occurred during the drought after individuals had resprouted (i.e. individuals survived fire, resprouted and then subsequently died). Physiological measurements of species with high mortality suggested that resprout stems were highly embolized and xylem hydraulic conductivities were close to zero during the peak of the drought. In addition, lignotubers of two of the three species experiencing high mortality were depleted of starch. Population densities of most shrub species declined after the drought compared with their prefire levels, with the exception of one drought tolerant obligate seeding species. Resprouting shrub species may deplete their carbohydrate reserves during the resprouting process, making them particularly vulnerable to drought because of the need to transpire water to acquire the CO2 that is used to supply energy to a large respiring root system. Drought appears to interact with fire by altering postfire shrub recovery and altering species abundances and composition of chaparral communities.
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Affiliation(s)
- R Brandon Pratt
- California State University, 9001 Stockdale Highway, Bakersfield, CA, 93311, USA
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