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Baca Cabrera JC, Vanderborght J, Couvreur V, Behrend D, Gaiser T, Nguyen TH, Lobet G. Root hydraulic properties: An exploration of their variability across scales. Plant Direct 2024; 8:e582. [PMID: 38590783 PMCID: PMC10999368 DOI: 10.1002/pld3.582] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/07/2023] [Revised: 02/26/2024] [Accepted: 03/05/2024] [Indexed: 04/10/2024]
Abstract
Root hydraulic properties are key physiological traits that determine the capacity of root systems to take up water, at a specific evaporative demand. They can strongly vary among species, cultivars or even within the same genotype, but a systematic analysis of their variation across plant functional types (PFTs) is still missing. Here, we reviewed published empirical studies on root hydraulic properties at the segment-, individual root-, or root system scale and determined its variability and the main factors contributing to it. This corresponded to a total of 241 published studies, comprising 213 species, including woody and herbaceous vegetation. We observed an extremely large range of variation (of orders of magnitude) in root hydraulic properties, but this was not caused by systematic differences among PFTs. Rather, the (combined) effect of factors such as root system age, driving force used for measurement, or stress treatments shaped the results. We found a significant decrease in root hydraulic properties under stress conditions (drought and aquaporin inhibition, p < .001) and a significant effect of the driving force used for measurement (hydrostatic or osmotic gradients, p < .001). Furthermore, whole root system conductance increased significantly with root system age across several crop species (p < .01), causing very large variation in the data (>2 orders of magnitude). Interestingly, this relationship showed an asymptotic shape, with a steep increase during the first days of growth and a flattening out at later stages of development. We confirmed this dynamic through simulations using a state-of-the-art computational model of water flow in the root system for a variety of crop species, suggesting common patterns across studies and species. These findings provide better understanding of the main causes of root hydraulic properties variations observed across empirical studies. They also open the door to better representation of hydraulic processes across multiple plant functional types and at large scales. All data collected in our analysis has been aggregated into an open access database (https://roothydraulic-properties.shinyapps.io/database/), fostering scientific exchange.
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Affiliation(s)
- Juan C. Baca Cabrera
- Institute of Bio‐ and Geoscience, Agrosphere (IBG‐3)Forschungszentrum Jülich GmbHJülichGermany
| | - Jan Vanderborght
- Institute of Bio‐ and Geoscience, Agrosphere (IBG‐3)Forschungszentrum Jülich GmbHJülichGermany
| | - Valentin Couvreur
- Earth and Life InstituteUniversité catholique de LouvainLouvain‐la‐NeuveBelgium
| | - Dominik Behrend
- Institute of Crop Science and Resources ConservationUniversity of BonnBonnGermany
| | - Thomas Gaiser
- Institute of Crop Science and Resources ConservationUniversity of BonnBonnGermany
| | - Thuy Huu Nguyen
- Institute of Crop Science and Resources ConservationUniversity of BonnBonnGermany
| | - Guillaume Lobet
- Institute of Bio‐ and Geoscience, Agrosphere (IBG‐3)Forschungszentrum Jülich GmbHJülichGermany
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Boursiac Y, Protto V, Rishmawi L, Maurel C. Experimental and conceptual approaches to root water transport. Plant Soil 2022; 478:349-370. [PMID: 36277078 PMCID: PMC9579117 DOI: 10.1007/s11104-022-05427-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2022] [Accepted: 04/03/2022] [Indexed: 05/05/2023]
Abstract
BACKGROUND Root water transport, which critically contributes to the plant water status and thereby plant productivity, has been the object of extensive experimental and theoretical studies. However, root systems represent an intricate assembly of cells in complex architectures, including many tissues at distinct developmental stages. Our comprehension of where and how molecular actors integrate their function in order to provide the root with its hydraulic properties is therefore still limited. SCOPE Based on current literature and prospective discussions, this review addresses how root water transport can be experimentally measured, what is known about the underlying molecular actors, and how elementary water transport processes are scaled up in numerical/mathematical models. CONCLUSIONS The theoretical framework and experimental procedures on root water transport that are in use today have been established a few decades ago. However, recent years have seen the appearance of new techniques and models with enhanced resolution, down to a portion of root or to the tissue level. These advances pave the way for a better comprehension of the dynamics of water uptake by roots in the soil.
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Affiliation(s)
- Yann Boursiac
- IPSiM, Univ Montpellier, CNRS, INRAE, Institut Agro, 34060 Montpellier, France
| | - Virginia Protto
- IPSiM, Univ Montpellier, CNRS, INRAE, Institut Agro, 34060 Montpellier, France
| | - Louai Rishmawi
- IPSiM, Univ Montpellier, CNRS, INRAE, Institut Agro, 34060 Montpellier, France
| | - Christophe Maurel
- IPSiM, Univ Montpellier, CNRS, INRAE, Institut Agro, 34060 Montpellier, France
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3
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Kurowska MM. Aquaporins in Cereals-Important Players in Maintaining Cell Homeostasis under Abiotic Stress. Genes (Basel) 2021; 12:genes12040477. [PMID: 33806192 PMCID: PMC8066221 DOI: 10.3390/genes12040477] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Revised: 03/18/2021] [Accepted: 03/23/2021] [Indexed: 12/27/2022] Open
Abstract
Cereal productivity is reduced by environmental stresses such as drought, heat, elevated CO2, salinity, metal toxicity and cold. Sometimes, plants are exposed to multiple stresses simultaneously. Plants must be able to make a rapid and adequate response to these environmental stimuli in order to restore their growing ability. The latest research has shown that aquaporins are important players in maintaining cell homeostasis under abiotic stress. Aquaporins are membrane intrinsic proteins (MIP) that form pores in the cellular membranes, which facilitate the movement of water and many other molecules such as ammonia, urea, CO2, micronutrients (silicon and boron), glycerol and reactive oxygen species (hydrogen peroxide) across the cell and intercellular compartments. The present review primarily focuses on the diversity of aquaporins in cereal species, their cellular and subcellular localisation, their expression and their functioning under abiotic stresses. Lastly, this review discusses the potential use of mutants and plants that overexpress the aquaporin-encoding genes to improve their tolerance to abiotic stress.
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Affiliation(s)
- Marzena Małgorzata Kurowska
- Institute of Biology, Biotechnology and Environmental Protection, Faculty of Natural Sciences, University of Silesia in Katowice, Jagiellońska 28, 40-032 Katowice, Poland
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Koch A, Meunier F, Vanderborght J, Garré S, Pohlmeier A, Javaux M. Functional-structural root-system model validation using a soil MRI experiment. J Exp Bot 2019; 70:2797-2809. [PMID: 30799498 PMCID: PMC6509106 DOI: 10.1093/jxb/erz060] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2018] [Accepted: 02/05/2019] [Indexed: 05/04/2023]
Abstract
For the first time, a functional-structural root-system model is validated by combining a tracer experiment monitored with magnetic resonance imaging and three-dimensional modeling of water and solute transport.
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Affiliation(s)
- Axelle Koch
- Earth and Life Institute – Environmental Sciences, UCLouvain, Louvain-la-Neuve, Belgium
| | - Félicien Meunier
- Earth and Life Institute – Environmental Sciences, UCLouvain, Louvain-la-Neuve, Belgium
- Computational and Applied Vegetation Ecology Lab, Ghent University, Ghent, Belgium
| | - Jan Vanderborght
- Institute of Bio- and Geosciences, IBG-3 Agrosphere, Forschungszentrum Jülich GmbH, Jülich, Germany
- Earth and Environmental Sciences, KU Leuven, Celestijnenlaan, Leuven, Belgium
| | - Sarah Garré
- Gembloux Agro-Bio Tech, Université de Liège, Passage des déportés, Gembloux, Belgium
| | - Andreas Pohlmeier
- Institute of Bio- and Geosciences, IBG-3 Agrosphere, Forschungszentrum Jülich GmbH, Jülich, Germany
| | - Mathieu Javaux
- Earth and Life Institute – Environmental Sciences, UCLouvain, Louvain-la-Neuve, Belgium
- Institute of Bio- and Geosciences, IBG-3 Agrosphere, Forschungszentrum Jülich GmbH, Jülich, Germany
- Correspondence:
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Kim YX, Ranathunge K, Lee S, Lee Y, Lee D, Sung J. Composite Transport Model and Water and Solute Transport across Plant Roots: An Update. Front Plant Sci 2018; 9:193. [PMID: 29503659 PMCID: PMC5820301 DOI: 10.3389/fpls.2018.00193] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2017] [Accepted: 02/01/2018] [Indexed: 05/19/2023]
Abstract
The present review examines recent experimental findings in root transport phenomena in terms of the composite transport model (CTM). It has been a well-accepted conceptual model to explain the complex water and solute flows across the root that has been related to the composite anatomical structure. There are three parallel pathways involved in the transport of water and solutes in roots - apoplast, symplast, and transcellular paths. The role of aquaporins (AQPs), which facilitate water flows through the transcellular path, and root apoplast is examined in terms of the CTM. The contribution of the plasma membrane bound AQPs for the overall water transport in the whole plant level was varying depending on the plant species, age of roots with varying developmental stages of apoplastic barriers, and driving forces (hydrostatic vs. osmotic). Many studies have demonstrated that the apoplastic barriers, such as Casparian bands in the primary anticlinal walls and suberin lamellae in the secondary cell walls, in the endo- and exodermis are not perfect barriers and unable to completely block the transport of water and some solute transport into the stele. Recent research on water and solute transport of roots with and without exodermis triggered the importance of the extension of conventional CTM adding resistances that arrange in series (epidermis, exodermis, mid-cortex, endodermis, and pericycle). The extension of the model may answer current questions about the applicability of CTM for composite water and solute transport of roots that contain complex anatomical structures with heterogeneous cell layers.
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Affiliation(s)
- Yangmin X. Kim
- Division of Soil and Fertilizer, National Institute of Agricultural Sciences, Rural Development Administration, Wanju, South Korea
| | - Kosala Ranathunge
- School of Biological Sciences, The University of Western Australia, Perth, WA, Australia
| | - Seulbi Lee
- Division of Soil and Fertilizer, National Institute of Agricultural Sciences, Rural Development Administration, Wanju, South Korea
| | - Yejin Lee
- Division of Soil and Fertilizer, National Institute of Agricultural Sciences, Rural Development Administration, Wanju, South Korea
| | - Deogbae Lee
- Division of Soil and Fertilizer, National Institute of Agricultural Sciences, Rural Development Administration, Wanju, South Korea
| | - Jwakyung Sung
- Division of Soil and Fertilizer, National Institute of Agricultural Sciences, Rural Development Administration, Wanju, South Korea
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Chen X, Li Y, He R, Ding Q. Phenotyping field-state wheat root system architecture for root foraging traits in response to environment×management interactions. Sci Rep 2018; 8:2642. [PMID: 29422488 PMCID: PMC5805786 DOI: 10.1038/s41598-018-20361-w] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2017] [Accepted: 01/16/2018] [Indexed: 01/26/2023] Open
Abstract
An important aspect of below-ground crop physiology is its root foraging performance, which is inherently related to root system architecture (RSA). A 2-yr field experiment was conducted and the field-state wheat RSA was phenotyped for root foraging trait (RFT). Four RSA-derived traits, i.e. Root horizontal angle (RHA), axial root expansion volume (AREV), RSA convex hull volume (CHV) and effective volume per unit root length (EVURL), were analyzed for RFTs in response to environment × management interactions. Results showed a dynamical RHA process but without statistical difference both within crop seasons and tillage treatments. AREV increased with root developmental stages, revealing an overall better root performance in the first year. However, tillage treatments did not induce observed difference within both crop seasons. CHV varied drastically from year to year and between tillage treatments, correlating well to the root length, but not with RHA. EVURL was both sensitive to tillage treatments and crop seasons, being a potential indicator for RFT. Above all, tillage effect on RFT was statistically far less than that induced by crop seasons. Pro/E assisted modeling can be used as an effective means for phenotyping integrated, RSA-derived, RFTs for root foraging response to induced environment × management interactions.
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Affiliation(s)
- Xinxin Chen
- College of Engineering, Nanjing Agricultural University/Key Laboratory of Intelligent Agricultural Equipment of Jiangsu Province, Nanjing, 210031, China
| | - Yinian Li
- College of Engineering, Nanjing Agricultural University/Key Laboratory of Intelligent Agricultural Equipment of Jiangsu Province, Nanjing, 210031, China
| | - Ruiyin He
- College of Engineering, Nanjing Agricultural University/Key Laboratory of Intelligent Agricultural Equipment of Jiangsu Province, Nanjing, 210031, China
| | - Qishuo Ding
- College of Engineering, Nanjing Agricultural University/Key Laboratory of Intelligent Agricultural Equipment of Jiangsu Province, Nanjing, 210031, China.
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7
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Blessing CH, Mariette A, Kaloki P, Bramley H. Profligate and conservative: water use strategies in grain legumes. J Exp Bot 2018; 69:349-369. [PMID: 29370385 DOI: 10.1093/jxb/erx415] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2017] [Accepted: 10/23/2017] [Indexed: 06/07/2023]
Abstract
Yields of grain legumes are constrained by available water. Thus, it is crucial to understand traits influencing water uptake and the efficiency of using water to produce biomass. Global comparisons and comparisons at specific locations reveal that water use of different grain legumes is very similar, which indicates that water use efficiency varies over a wide range due to differences in biomass and yield. Moreover, yield increases more per millimetre of water used in cool season grain legumes than warm season species. Although greater contrasts have been observed across species and genotypes at the pot and lysimeter level, agronomic factors need to be taken into account when scaling those studies to field-level responses. Conservative water use strategies in grain legumes such as low stomatal conductance as approximated by low photosynthetic carbon isotope discrimination reduces yield potential, whereas temporal adjustments of stomatal conductance within the growing season and in response to environmental factors (such as vapour pressure deficit) helps to optimize the trade-off between carbon gain and water loss. Furthermore, improved photosynthetic capacity, reduced mesophyll conductance, reduced boundary layer, and re-fixation of respired CO2 were identified as traits that are beneficial without water deficit, but also under terminal and transient drought. Genotypic variability in some grain legume species has been observed for several traits that influence water use, water use efficiency, and yield, including root length and the temporal pattern of water use, but even more variation is expected from wild relatives. Albeit that N2 fixation decreases under drought, its impact on water use is still largely unknown, but the nitrogen source influences gas exchange and, thus, transpiration efficiency. This review concludes that conservative traits are needed under conditions of terminal drought to help maintain soil moisture until the pod-filling period, but profligate traits, if tightly regulated, are important under conditions of transient drought in order to profit from short intermittent periods of available soil moisture.
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Affiliation(s)
- Carola H Blessing
- The University of Sydney, School of Life and Environmental Sciences, Sydney Institute of Agriculture, Sydney, New South Wales, Australia
| | - Alban Mariette
- The University of Sydney, Plant Breeding Institute, Narrabri, New South Wales, Australia
- Biology Department, Université de Rennes 1, Campus de Beaulieu, Rennes Cedex, France
| | - Peter Kaloki
- The University of Sydney, School of Life and Environmental Sciences, Sydney Institute of Agriculture, Sydney, New South Wales, Australia
- The University of Sydney, Plant Breeding Institute, Narrabri, New South Wales, Australia
| | - Helen Bramley
- The University of Sydney, School of Life and Environmental Sciences, Sydney Institute of Agriculture, Sydney, New South Wales, Australia
- The University of Sydney, Plant Breeding Institute, Narrabri, New South Wales, Australia
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8
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Tyerman SD, Wignes JA, Kaiser BN. Root Hydraulic and Aquaporin Responses to N Availability. In: Chaumont F, Tyerman SD, editors. Plant Aquaporins. Cham: Springer International Publishing; 2017. pp. 207-36. [DOI: 10.1007/978-3-319-49395-4_10] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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9
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Saradadevi R, Bramley H, Palta JA, Siddique KHM. Stomatal behaviour under terminal drought affects post-anthesis water use in wheat. Funct Plant Biol 2017; 44:279-289. [PMID: 32480563 DOI: 10.1071/fp16078] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2016] [Accepted: 10/23/2016] [Indexed: 05/22/2023]
Abstract
Post-anthesis water use is important for grain yield in wheat under drought because this water is immediately used for grain filling. The aim of this study was to determine whether root capacity for water uptake from deeper layers in the soil profile differed between two genotypes with contrasting stomatal behaviour under terminal drought. The wheat cultivar Drysdale and the breeding line IGW-3262 were grown in 1m deep pots in a glasshouse under well-watered conditions until anthesis, when three watering treatments were imposed: (i) watering maintained at 90% pot soil water capacity (WW), (ii) watering withheld but supplementary watering supplied to the bottom 30cm of the pot to keep this layer of the soil profile wet until physiological maturity (WB) and (iii) watering completely withheld (WS). Stomatal conductance, post-anthesis water use and water use efficiency, and grain yield were measured. Post-anthesis water use in Drysdale was similar in the WB and WW treatments, while in IGW-3262 it was 30% less in the WB treatment than in the WW treatment. In the WB treatment as the top soil dried, stomatal closure was faster in IGW-3262 than in Drysdale, which may have affected the capacity of roots to uptake available water at depth. The reduction in post-anthesis water use in IGW-3262 resulted in a decline in grain yield.
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Affiliation(s)
- Renu Saradadevi
- School of Plant Biology, The University of Western Australia, LB 5005 Perth, WA 6001, Australia
| | - Helen Bramley
- Plant Breeding Institute, Faculty of Agriculture and Environment, The University of Sydney, 12656 Newell Highway, Narrabri NSW 2390, Australia
| | - Jairo A Palta
- School of Plant Biology, The University of Western Australia, LB 5005 Perth, WA 6001, Australia
| | - Kadambot H M Siddique
- The UWA Institute of Agriculture, The University of Western Australia, LB 5005 Perth, WA 6001, Australia
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10
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Abstract
Plants require the capacity for quick and precise recognition of external stimuli within their environment for survival. Upon exposure to biotic (herbivores and pathogens) or abiotic stressors (environmental conditions), plants can activate hydraulic, chemical, or electrical long-distance signals to initiate systemic stress responses. A plant's stress reactions can be highly precise and orchestrated in response to different stressors or stress combinations. To date, an array of information is available on plant responses to single stressors. However, information on simultaneously occurring stresses that represent either multiple, within, or across abiotic and biotic stress types is nascent. Likewise, the crosstalk between hydraulic, chemical, and electrical signaling pathways and the importance of each individual signaling type requires further investigation in order to be fully understood. The overlapping presence and speed of the signals upon plant exposure to various stressors makes it challenging to identify the signal initiating plant systemic stress/defense responses. Furthermore, it is thought that systemic plant responses are not transmitted by a single pathway, but rather by a combination of signals enabling the transmission of information on the prevailing stressor(s) and its intensity. In this review, we summarize the mode of action of hydraulic, chemical, and electrical long-distance signals, discuss their importance in information transmission to biotic and abiotic stressors, and suggest future research directions.
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Affiliation(s)
- Annika E Huber
- Cornell University, School of Integrative Plant Science, Ithaca, NY 14850, USA
| | - Taryn L Bauerle
- Cornell University, School of Integrative Plant Science, Ithaca, NY 14850, USA
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11
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Bramley H, Bitter R, Zimmermann G, Zimmermann U. Simultaneous recording of diurnal changes in leaf turgor pressure and stem water status of bread wheat reveal variation in hydraulic mechanisms in response to drought. Funct Plant Biol 2015; 42:1001-1009. [PMID: 32480739 DOI: 10.1071/fp15087] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Accepted: 07/06/2015] [Indexed: 06/11/2023]
Abstract
Information about water relations within crop canopies is needed to improve our understanding of canopy resource distribution and crop productivity. In this study, we examined the dehydration/rehydration kinetics of different organs of wheat plants using ZIM-probes that continuously monitor water status non-destructively. ZIM-probes were clamped to the flag leaf and penultimate leaf of the same stem to monitor changes in turgor pressure, and a novel stem probe was clamped to the peduncle (just below the spike of the same stem) to monitor changes in stem water status. All organs behaved similarly under well-watered conditions, dehydrating and recovering at the same times of day. When water was withheld, the behaviour diverged, with the leaves showing gradual dehydration and incomplete recovery in leaf turgor pressure during the night, but the stem was affected to a lesser extent. Penultimate leaves were the most severely affected, reaching turgor loss point before the flag leaf. Upon rewatering, turgor pressure recovered but the output patch-pressure of the probes (Pp) oscillated at ~30min periods in all organs of most plants (n=4). Oscillations in Pp were attributed to oscillations in stomatal opening and appear to only occur above a threshold light intensity. The mechanisms identified in this study will be beneficial for crop productivity because the flag leaf is the source of most photoassimilates in developing grains, so the plant's ability to maintain flag leaf hydration at the expense of older leaves should moderate the impact of drought on yield. Stomatal oscillations could increase water use efficiency as the plant attempts to rehydrate after drought.
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Affiliation(s)
- Helen Bramley
- Plant Breeding Institute, Faculty of Agriculture and Environment, The University of Sydney, 12656 Newell Highway, Narrabri, NSW 2390, Australia
| | - Rebecca Bitter
- ZIM-Plant Technology GmbH, Neuendorfstr. 19, 16761 Hennigsdorf, Germany
| | | | - Ulrich Zimmermann
- ZIM-Plant Technology GmbH, Neuendorfstr. 19, 16761 Hennigsdorf, Germany
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12
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Chaumont F, Tyerman SD. Aquaporins: highly regulated channels controlling plant water relations. Plant Physiol 2014; 164:1600-18. [PMID: 24449709 PMCID: PMC3982727 DOI: 10.1104/pp.113.233791] [Citation(s) in RCA: 345] [Impact Index Per Article: 34.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2013] [Accepted: 01/19/2014] [Indexed: 05/18/2023]
Abstract
Plant growth and development are dependent on tight regulation of water movement. Water diffusion across cell membranes is facilitated by aquaporins that provide plants with the means to rapidly and reversibly modify water permeability. This is done by changing aquaporin density and activity in the membrane, including posttranslational modifications and protein interaction that act on their trafficking and gating. At the whole organ level aquaporins modify water conductance and gradients at key "gatekeeper" cell layers that impact on whole plant water flow and plant water potential. In this way they may act in concert with stomatal regulation to determine the degree of isohydry/anisohydry. Molecular, physiological, and biophysical approaches have demonstrated that variations in root and leaf hydraulic conductivity can be accounted for by aquaporins but this must be integrated with anatomical considerations. This Update integrates these data and emphasizes the central role played by aquaporins in regulating plant water relations.
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Affiliation(s)
| | - Stephen D. Tyerman
- Institut des Sciences de la Vie, Université catholique de Louvain, Croix du Sud 4–L7.07.14, B–1348 Louvain-la-Neuve, Belgium (F.C.); and
- Australian Research Council Centre of Excellence in Plant Energy Biology, Waite Research Institute, School of Agriculture, Food, and Wine, University of Adelaide, Waite Campus PMB 1, Glen Osmond, South Australia 5064, Australia (S.D.T.)
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13
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Vandeleur RK, Sullivan W, Athman A, Jordans C, Gilliham M, Kaiser BN, Tyerman SD. Rapid shoot-to-root signalling regulates root hydraulic conductance via aquaporins. Plant Cell Environ 2014; 37:520-38. [PMID: 23926961 DOI: 10.1111/pce.12175] [Citation(s) in RCA: 95] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2013] [Revised: 07/15/2013] [Accepted: 07/19/2013] [Indexed: 05/03/2023]
Abstract
We investigated how root hydraulic conductance (normalized to root dry weight, Lo ) is regulated by the shoot. Shoot topping (about 30% reduction in leaf area) reduced Lo of grapevine (Vitis vinifera L.), soybean (Glycine max L.) and maize (Zea mays L.) by 50 to 60%. More detailed investigations with soybean and grapevine showed that the reduction in Lo was not correlated with the reduction in leaf area, and shading or cutting single leaves had a similar effect. Percentage reduction in Lo was largest when initial Lo was high in soybean. Inhibition of Lo by weak acid (low pH) was smaller after shoot damage or leaf shading. The half time of reduction in Lo was approximately 5 min after total shoot decapitation. These characteristics indicate involvement of aquaporins. We excluded phloem-borne signals and auxin-mediated signals. Xylem-mediated hydraulic signals are possible since turgor rapidly decreased within root cortex cells after shoot topping. There was a significant reduction in the expression of several aquaporins in the plasma membrane intrinsic protein (PIP) family of both grapevine and soybean. In soybean, there was a five- to 10-fold reduction in GmPIP1;6 expression over 0.5-1 h which was sustained over the period of reduced Lo .
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Affiliation(s)
- Rebecca K Vandeleur
- Australian Research Council Centre of Excellence in Plant Energy Biology, Waite Research Institute, School of Agriculture Food and Wine, University of Adelaide, Waite Campus PMB 1, Glen Osmond, South Australia, 5064, Australia
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14
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Abstract
The thermodynamics of root pressure remains an enigma up to the present day. Water is transported radially into xylem vessels, under some conditions even when the xylem sap is more dilute than the ambient medium (soil solution). It is suggested here that water secretion across the plasma membrane of xylem parenchyma cells is driven by a co-transport of water and solutes as previously shown for mammalian epithelia (Zeuthen T. 2010. Water-transporting proteins. Journal of Membrane Biology 234, 57-73.). This process could drive volume flow 'energetically uphill', against the free energy gradient of water. According to the model, solutes released by xylem parenchyma cells are subsequently retrieved from the sap at the expense of metabolic energy to maintain the concentration gradient that drives the water secretion. Transporters of the CCC type known to mediate water secretion in mammalian cells have also been found in Arabidopsis and in rice. The mechanism proposed here for root pressure could also explain refilling of embolized vessels. Moreover, it could contribute to long-distance water transport in trees when the cohesion-tension mechanism of water ascent fails. This is discussed with respect to the old and the more recent literature on these subjects.
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Affiliation(s)
- Lars H Wegner
- Karlsruhe Institute of Technology, Institute of Botany I, and Institute of Pulsed Power and Microwave Technology, Campus North, Building 630, Hermann-v-Helmholtz Platz 1, D-76344 Eggenstein-Leopoldshafen, Germany
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Ehrenberger W, Rüger S, Rodríguez-Domínguez CM, Díaz-Espejo A, Fernández JE, Moreno J, Zimmermann D, Sukhorukov VL, Zimmermann U. Leaf patch clamp pressure probe measurements on olive leaves in a nearly turgorless state. Plant Biol (Stuttg) 2012; 14:666-674. [PMID: 22288430 DOI: 10.1111/j.1438-8677.2011.00545.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The non-invasive leaf patch clamp pressure (LPCP) probe measures the attenuated pressure of a leaf patch, P(p) , in response to an externally applied magnetic force. P(p) is inversely coupled with leaf turgor pressure, P(c) , i.e. at high P(c) values the P(p) values are small and at low P(c) values the P(p) values are high. This relationship between P(c) and P(p) could also be verified for 2-m tall olive trees under laboratory conditions using the cell turgor pressure probe. When the laboratory plants were subjected to severe water stress (P(c) dropped below ca. 50 kPa), P(p) curves show reverse diurnal changes, i.e. during the light regime (high transpiration) a minimum P(p) value, and during darkness a peak P(p) value is recorded. This reversal of the P(p) curves was completely reversible. Upon watering, the original diurnal P(p) changes were re-established within 2-3 days. Olive trees in the field showed a similar turnover of the shape of the P(p) curves upon drought, despite pronounced fluctuations in microclimate. The reversal of the P(p) curves is most likely due to accumulation of air in the leaves. This assumption was supported with cross-sections through leaves subjected to prolonged drought. In contrast to well-watered leaves, microscopic inspection of leaves exhibiting inverse diurnal P(p) curves revealed large air-filled areas in parenchyma tissue. Significantly larger amounts of air could also be extracted from water-stressed leaves than from well-watered leaves using the cell turgor pressure probe. Furthermore, theoretical analysis of the experimental P(p) curves shows that the propagation of pressure through the nearly turgorless leaf must be exclusively dictated by air. Equations are derived that provide valuable information about the water status of olive leaves close to zero P(c) .
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Affiliation(s)
- W Ehrenberger
- Lehrstuhl für Biotechnologie, Biozentrum, Universität Würzburg, Würzburg, Germany
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16
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Rewald B, Raveh E, Gendler T, Ephrath JE, Rachmilevitch S. Phenotypic plasticity and water flux rates of Citrus root orders under salinity. J Exp Bot 2012; 63:2717-27. [PMID: 22268156 PMCID: PMC3346233 DOI: 10.1093/jxb/err457] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2011] [Revised: 12/16/2011] [Accepted: 12/19/2011] [Indexed: 05/21/2023]
Abstract
Knowledge about the root system structure and the uptake efficiency of root orders is critical to understand the adaptive plasticity of plants towards salt stress. Thus, this study describes the phenological and physiological plasticity of Citrus volkameriana rootstocks under severe NaCl stress on the level of root orders. Phenotypic root traits known to influence uptake processes, for example frequency of root orders, specific root area, cortical thickness, and xylem traits, did not change homogeneously throughout the root system, but changes after 6 months under 90 mM NaCl stress were root order specific. Chloride accumulation significantly increased with decreasing root order, and the Cl(-) concentration in lower root orders exceeded those in leaves. Water flux densities of first-order roots decreased to <20% under salinity and did not recover after stress release. The water flux densities of higher root orders changed marginally under salinity and increased 2- to 6-fold in second and third root orders after short-term stress release. Changes in root order frequency, morphology, and anatomy indicate rapid and major modification of C. volkameriana root systems under salt stress. Reduced water uptake under salinity was related to changes of water flux densities among root orders and to reduced root surface areas. The importance of root orders for water uptake changed under salinity from root tips towards higher root orders. The root order-specific changes reflect differences in vulnerability (indicated by the salt accumulation) and ontogenetic status, and point to functional differences among root orders under high salinity.
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Affiliation(s)
- Boris Rewald
- French Associates Institute for Agriculture and Biotechnology of Drylands, Ben-Gurion University of the Negev, Israel.
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17
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Abstract
By insertion into an individual xylem vessel at the root base, the multifunctional xylem probe allows the monitoring of the xylem pressure, the radial electrical gradients in the root (the so-called trans-root potential, TRP), as well as the activity of a particular ion such as K(+) in the xylem sap of intact, transpiring plants. The biophysical and physiological significance of these parameters with respect to salt stress is briefly explained, and the assembly of the probe, the setup used for these measurements, and the experimental procedure are outlined in detail.
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Affiliation(s)
- Lars H Wegner
- Karlsruhe Institute of Technology, Institute of Botany I and Institute of Pulsed Power and Microwave Technology, Eggenstein-Leopoldshafen, Germany.
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Kudoyarova G, Veselova S, Hartung W, Farhutdinov R, Veselov D, Sharipova G. Involvement of root ABA and hydraulic conductivity in the control of water relations in wheat plants exposed to increased evaporative demand. Planta 2011; 233:87-94. [PMID: 20924765 DOI: 10.1007/s00425-010-1286-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/22/2010] [Accepted: 09/20/2010] [Indexed: 05/03/2023]
Abstract
We studied the possible involvement of ABA in the control of water relations under conditions of increased evaporative demand. Warming the air by 3°C increased stomatal conductance and raised transpiration rates of hydroponically grown Triticum durum plants while bringing about a temporary loss of relative water content (RWC) and immediate cessation of leaf extension. However, both RWC and extension growth recovered within 30 min although transpiration remained high. The restoration of leaf hydration and growth were enabled by increased root hydraulic conductivity after increasing the air temperature. The use of mercuric chloride (an inhibitor of water channels) to interfere with the rise on root hydraulic conductivity hindered the restoration of extension growth. Air warming increased ABA content in roots and decreased it in shoots. We propose this redistribution of ABA in favour of the roots which increased the root hydraulic conductivity sufficiently to permit rapid recovery of shoot hydration and leaf elongation rates without the involvement of stomatal closure. This proposal is based on known ability of ABA to increase hydraulic conductivity confirmed in these experiments by measuring the effect of exogenous ABA on osmotically driven flow of xylem sap from the roots. Accumulation of root ABA was mainly the outcome of increased export from the shoots. When phloem transport in air-warmed plants was inhibited by cooling the shoot base this prevented ABA enrichment of the roots and favoured an accumulation of ABA in the shoot. As a consequence, stomata closed.
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19
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Takase T, Ishikawa H, Murakami H, Kikuchi J, Sato-Nara K, Suzuki H. The Circadian Clock Modulates Water Dynamics and Aquaporin Expression in Arabidopsis Roots. ACTA ACUST UNITED AC 2010; 52:373-83. [DOI: 10.1093/pcp/pcq198] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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20
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Knipfer T, Fricke W. Root pressure and a solute reflection coefficient close to unity exclude a purely apoplastic pathway of radial water transport in barley (Hordeum vulgare). New Phytol 2010; 187:159-170. [PMID: 20412443 DOI: 10.1111/j.1469-8137.2010.03240.x] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
*Aquaporins can contribute to the control of root water uptake, provided that at least one membrane is crossed between the root medium and the xylem and that water does not move only along the apoplast. In the present study we have critically assessed the possibility of such a purely apoplastic pathway. *A range of methods were used to analyse root water flow (root pressure probe, root exudation, vacuum perfusion and cell pressure probe) and associated driving forces (gradients in hydrostatic pressure and osmolality). These methods were complemented by theoretical approaches in which we predicted, for a particular main pathway of water movement, values for root pressure and osmolality and compared these with measured values. *The mere existence of root pressure excludes the possibility of a purely apoplastic pathway of radial water uptake. A membrane(s) must be crossed. Equilibrium measurements of gradients in hydrostatic and osmotic pressure between the root medium and the xylem point to a root reflection coefficient for solutes close to 1.0. *The generally accepted composite model of water transport across roots should be revised. Barley (Hordeum vulgare) roots behave as perfect osmometers. Root reflection coefficients significantly smaller than unity may be experimental artefacts.
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Affiliation(s)
- Thorsten Knipfer
- School of Biology and Environmental Science, Science Centre West, University College Dublin, Belfield, Dublin 4, Ireland
| | - Wieland Fricke
- School of Biology and Environmental Science, Science Centre West, University College Dublin, Belfield, Dublin 4, Ireland
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21
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Abstract
In standard techniques (root pressure probe or high-pressure flowmeter), the hydraulic conductivity of roots is calculated from transients of root pressure using responses following step changes in volume or pressure, which may be affected by a storage of water in the stele. Storage effects were examined using both experimental data of root pressure relaxations and clamps and a physical capacity model. Young roots of corn and barley were treated as a three-compartment system, comprising a serial arrangement of xylem/probe, stele and outside medium/cortex. The hydraulic conductivities of the endodermis and of xylem vessels were derived from experimental data. The lower limit of the storage capacity of stelar tissue was caused by the compressibility of water. This was subsequently increased to account for realistic storage capacities of the stele. When root water storage was varied over up to five orders of magnitude, the results of simulations showed that storage effects could not explain the experimental data, suggesting a major contribution of effects other than water storage. It is concluded that initial water flows may be used to measure root hydraulic conductivity provided that the volumes of water used are much larger than the volumes stored.
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Affiliation(s)
- Ankur Joshi
- Department of Plant Ecology, Bayreuth University, D-95440 Bayreuth, Germany
| | - Thorsten Knipfer
- School of Biology and Environmental Science, University College of Dublin, Belfield, Dublin 4, Ireland
| | - Ernst Steudle
- Department of Plant Ecology, Bayreuth University, D-95440 Bayreuth, Germany
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Bramley H, Turner NC, Turner DW, Tyerman SD. Roles of morphology, anatomy, and aquaporins in determining contrasting hydraulic behavior of roots. Plant Physiol 2009; 150:348-64. [PMID: 19321713 PMCID: PMC2675714 DOI: 10.1104/pp.108.134098] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2008] [Accepted: 03/19/2009] [Indexed: 05/18/2023]
Abstract
The contrasting hydraulic properties of wheat (Triticum aestivum), narrow-leafed lupin (Lupinus angustifolius), and yellow lupin (Lupinus luteus) roots were identified by integrating measurements of water flow across different structural levels of organization with anatomy and modeling. Anatomy played a major role in root hydraulics, influencing axial conductance (L(ax)) and the distribution of water uptake along the root, with a more localized role for aquaporins (AQPs). Lupin roots had greater L(ax) than wheat roots, due to greater xylem development. L(ax) and root hydraulic conductance (L(r)) were related to each other, such that both variables increased with distance from the root tip in lupin roots. L(ax) and L(r) were constant with distance from the tip in wheat roots. Despite these contrasting behaviors, the hydraulic conductivity of root cells (Lp(c)) was similar for all species and increased from the root surface toward the endodermis. Lp(c) was largely controlled by AQPs, as demonstrated by dramatic reductions in Lp(c) by the AQP blocker mercury. Modeling the root as a series of concentric, cylindrical membranes, and the inhibition of AQP activity at the root level, indicated that water flow in lupin roots occurred primarily through the apoplast, without crossing membranes and without the involvement of AQPs. In contrast, water flow across wheat roots crossed mercury-sensitive AQPs in the endodermis, which significantly influenced L(r). This study demonstrates the importance of examining root morphology and anatomy in assessing the role of AQPs in root hydraulics.
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Affiliation(s)
- Helen Bramley
- School of Agriculture, Food, and Wine, University of Adelaide , Plant Research Centre, Glen Osmond, South Australia 5064, Australia.
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Wegner LH, Zimmermann U. Hydraulic conductance and K+ transport into the xylem depend on radial volume flow, rather than on xylem pressure, in roots of intact, transpiring maize seedlings. New Phytol 2009; 181:361-373. [PMID: 19121033 DOI: 10.1111/j.1469-8137.2008.02662.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The investigation of transport processes in roots has so far been hampered by a lack of adequate methods to study water and solute transport simultaneously in intact, transpiring plants. The role of xylem tension in regulating volume flow and nutrient transport could not be addressed properly. In order to overcome limitations of conventional, massive-invasive methods, a gravimetric technique was used to measure water uptake by maize roots while simultaneously recording xylem pressure and xylem K(+) activity in individual xylem vessels by means of a K(+)-selective xylem probe. This minimal-invasive approach allowed the calculation of the radial K(+)flux into the root xylem and the radial root hydraulic conductance on transpiring seedlings. By changing the light regime or the osmotic pressure of the external solution, radial water and K(+) flux could be varied in order to study the interaction between water and solute transport. A major finding was that both radial K(+) transport and hydraulic conductance strongly depended on radial volume flow, whereas xylem pressure had little (if any) effect on these parameters. Results are discussed with respect to relevant membrane transport processes and their regulation by volume flow.
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Affiliation(s)
- Lars H Wegner
- Lehrstuhl für Biotechnologie, Biozentrum, Universität Würzburg, D-97074 Würzburg, Germany;Present address: Plant Bioelectrics Group, Karlsruhe Institute of Technology, Campus North, Building 630, Hermann-v-Helmholtz Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
| | - Ulrich Zimmermann
- Lehrstuhl für Biotechnologie, Biozentrum, Universität Würzburg, D-97074 Würzburg, Germany;Present address: Plant Bioelectrics Group, Karlsruhe Institute of Technology, Campus North, Building 630, Hermann-v-Helmholtz Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
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24
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Abstract
Using the root pressure probe in the pressure clamping (PC) mode, the impact of internal unstirred layers (USLs) was quantified for young corn roots, both in experiments and in computer simulations applying the convection/diffusion model of Knipfer et al. In the experiments, water flows (J(Vr)s) during PC were analysed in great detail, showing that J(Vr)s (and the apparent root hydraulic conductivity) were high during early stages of PC and declined rapidly during the first 80 s of clamping to a steady-state value of 40-30% of the original. The comparison of experimental results with simulations showed that, during PC, internal USLs at the inner surface of the endodermis substantially modify the overall force driving the water. As a consequence, J(Vr) and Lp(r) were inhibited. Effects of internal USLs were minimized when using the pressure relaxation mode, when internal USLs had not yet developed. Additional stop-clamp experiments and experiments where the endodermis was punctured to reduce the effect of internal USLs verified the existence of internal USLs during PC. Data indicated that the role of pressure propagation along the root xylem for both PC and pressure relaxation modes should be small, as should the effects of filling of the capacities during root pressure probe experiments, which are discussed as an alternative model. The results supported the idea that concentration polarization effects at the endodermis (internal USLs) cause a serious problem whenever relatively large amounts of water (xylem sap) are radially moved across the root, such as during PC or when using the high-pressure flow meter technique.
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Affiliation(s)
- Thorsten Knipfer
- Department of Plant Ecology, Bayreuth University, D-95440 Bayreuth, Germany.
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