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Wegner LH. Empowering roots-Some current aspects of root bioenergetics. FRONTIERS IN PLANT SCIENCE 2022; 13:853309. [PMID: 36051301 PMCID: PMC9424547 DOI: 10.3389/fpls.2022.853309] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/12/2022] [Accepted: 07/15/2022] [Indexed: 06/15/2023]
Abstract
Roots of higher plants provide the shoot with nutrients and water. In exchange, they receive photosynthates, which serve both as energy source and building blocks for maintenance and growth. While studies in plant bioenergetics used to focus on photosynthesis, several more recent findings also aroused or renewed interest in energy conversion and allocation in roots. Root building costs were identified as a long-undervalued trait, which turned out to be highly relevant for stress tolerance and nutrient use efficiency. Reduced building costs per root length (e.g., by aerenchyma formation or by increasing the cell size) are beneficial for exploring the soil for nutrient-rich patches, especially in low-input agrosystems. Also, an apparent mismatch was frequently found between the root energy budget in the form of the ATP pool on the one side and the apparent costs on the other side, particularly the costs of membrane transport under stress conditions, e.g., the Na+ detoxification costs resulting from Na+ sequestration at the plasma membrane. Ion transport across the plasma membrane (and also endomembranes) is coupled to the proton motive force usually believed to be exclusively generated by H+ ATPases. Recently, an alternative mechanism, the biochemical pH clamp, was identified which relies on H+ formation and binding in the apoplast and the cytosol, respectively, driven by metabolism (so-called active buffering). On this background, several aspects of root bioenergetics are discussed. These are (1) root respiration in soil, with a critical view on calorimetric vs. gas exchange measurements; (2) processes of energy conversion in mitochondria with a special focus on the role of the alternative oxidases, which allow adjusting carbon flow through metabolic pathways to membrane transport processes; and (3) energy allocation, in particular to transport across the plasma membrane forming the interface to soil solution. A concluding remark is dedicated to modeling root bioenergetics for optimizing further breeding strategies. Apparent "energy spoilers" may bestow the plant with a yet unidentified advantage only unfolding their beneficial effect under certain environmental conditions.
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Tyerman SD, McGaughey SA, Qiu J, Yool AJ, Byrt CS. Adaptable and Multifunctional Ion-Conducting Aquaporins. ANNUAL REVIEW OF PLANT BIOLOGY 2021; 72:703-736. [PMID: 33577345 DOI: 10.1146/annurev-arplant-081720-013608] [Citation(s) in RCA: 43] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Aquaporins function as water and neutral solute channels, signaling hubs, disease virulence factors, and metabolon components. We consider plant aquaporins that transport ions compared to some animal counterparts. These are candidates for important, as yet unidentified, cation and anion channels in plasma, tonoplast, and symbiotic membranes. For those individual isoforms that transport ions, water, and gases, the permeability spans 12 orders of magnitude. This requires tight regulation of selectivity via protein interactions and posttranslational modifications. A phosphorylation-dependent switch between ion and water permeation in AtPIP2;1 might be explained by coupling between the gates of the four monomer water channels and the central pore of the tetramer. We consider the potential for coupling between ion and water fluxes that could form the basis of an electroosmotic transducer. A grand challenge in understanding the roles of ion transporting aquaporins is their multifunctional modes that are dependent on location, stress, time, and development.
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Affiliation(s)
- Stephen D Tyerman
- Australian Research Council (ARC) Centre of Excellence in Plant Energy Biology, School of Agriculture, Food and Wine, University of Adelaide, Glen Osmond, South Australia 5064, Australia; ,
| | - Samantha A McGaughey
- ARC Centre of Excellence for Translational Photosynthesis, Division of Plant Sciences, Research School of Biology, Australian National University, Acton, Australian Capital Territory 0200, Australia; ,
| | - Jiaen Qiu
- Australian Research Council (ARC) Centre of Excellence in Plant Energy Biology, School of Agriculture, Food and Wine, University of Adelaide, Glen Osmond, South Australia 5064, Australia; ,
| | - Andrea J Yool
- Adelaide Medical School, University of Adelaide, Adelaide, South Australia 5005, Australia;
| | - Caitlin S Byrt
- ARC Centre of Excellence for Translational Photosynthesis, Division of Plant Sciences, Research School of Biology, Australian National University, Acton, Australian Capital Territory 0200, Australia; ,
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Schenk HJ, Jansen S, Hölttä T. Positive pressure in xylem and its role in hydraulic function. THE NEW PHYTOLOGIST 2021; 230:27-45. [PMID: 33206999 DOI: 10.1111/nph.17085] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2020] [Accepted: 10/13/2020] [Indexed: 05/29/2023]
Abstract
Although transpiration-driven transport of xylem sap is well known to operate under absolute negative pressure, many terrestrial, vascular plants show positive xylem pressure above atmospheric pressure on a seasonal or daily basis, or during early developmental stages. The actual location and mechanisms behind positive xylem pressure remain largely unknown, both in plants that show seasonal xylem pressure before leaf flushing, and those that show a diurnal periodicity of bleeding and guttation. Available evidence shows that positive xylem pressure can be driven based on purely physical forces, osmotic exudation into xylem conduits, or hydraulic pressure in parenchyma cells associated with conduits. The latter two mechanisms may not be mutually exclusive and can be understood based on a similar modelling scenario. Given the renewed interest in positive xylem pressure, this review aims to provide a constructive way forward by discussing similarities and differences of mechanistic models, evaluating available evidence for hydraulic functions, such as rehydration of tissues, refilling of water stores, and embolism repair under positive pressure, and providing recommendations for future research, including methods that avoid or minimise cutting artefacts.
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Affiliation(s)
- H Jochen Schenk
- Department of Biological Science, California State University Fullerton, PO Box 6850, Fullerton, CA, 92834, USA
| | - Steven Jansen
- Institute of Systematic Botany and Ecology, Ulm University, Albert-Einstein-Allee 11, Ulm, D-89081, Germany
| | - Teemu Hölttä
- Faculty of Agriculture and Forestry, Institute for Atmospheric and Earth System Research/Forest Sciences, University of Helsinki, PO Box 27, Helsinki, FI-00014, Finland
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Volkov V, Schwenke H. A Quest for Mechanisms of Plant Root Exudation Brings New Results and Models, 300 Years after Hales. PLANTS 2020; 10:plants10010038. [PMID: 33375713 PMCID: PMC7823307 DOI: 10.3390/plants10010038] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Revised: 12/20/2020] [Accepted: 12/21/2020] [Indexed: 12/27/2022]
Abstract
The review summarizes some of our current knowledge on the phenomenon of exudation from the cut surface of detached roots with emphasis on results that were mostly established over the last fifty years. The phenomenon is quantitatively documented in the 18th century (by Hales in 1727). By the 19th century, theories mainly ascribed exudation to the secretion of living root cells. The 20th century favored the osmometer model of root exudation. Nevertheless, growing insights into the mechanisms of water transport and new or rediscovered observations stimulated the quest for a more adequate exudation model. The historical overview shows how understanding of exudation changed with time following experimental opportunities and novel ideas from different areas of knowledge. Later theories included cytoskeleton-dependent micro-pulsations of turgor in root cells to explain the observed water exudation. Recent progress in experimental biomedicine led to detailed study of channels and transporters for ion transport via cellular membranes and to the discovery of aquaporins. These universal molecular entities have been incorporated to the more complex models of water transport via plant roots. A new set of ideas and explanations was based on cellular osmoregulation by mechanosensitive ion channels. Thermodynamic calculations predicted the possibility of water transport against osmotic forces based on co-transport of water with ions via cation-chloride cotransporters. Recent observations of rhizodermis exudation, exudation of roots without an external aqueous medium, segments cut from roots, pulses of exudation, a phase shifting of water uptake and exudation, and of effects of physiologically active compounds (like ion channel blockers, metabolic agents, and cytoskeletal agents) will likely refine our understanding of the phenomenon. So far, it seems that more than one mechanism is responsible for root pressure and root exudation, processes which are important for refilling of embolized xylem vessels. However, recent advances in ion and water transport research at the molecular level suggest potential future directions to understanding of root exudation and new models awaiting experimental testing.
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Affiliation(s)
- Vadim Volkov
- Department of Plant Sciences, College of Agricultural and Environmental Sciences, University of California, Davis, CA 95616, USA
- K.A. Timiriazev Institute of Plant Physiology RAS, 35 Botanicheskaya St., Moscow 127276, Russia
- Correspondence: (V.V.); (H.S.)
| | - Heiner Schwenke
- Max Planck Institute for the History of Science, Boltzmannstraße 22, 14195 Berlin, Germany
- Correspondence: (V.V.); (H.S.)
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5
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Fricke W. Energy costs of salinity tolerance in crop plants: night-time transpiration and growth. THE NEW PHYTOLOGIST 2020; 225:1152-1165. [PMID: 30834533 DOI: 10.1111/nph.15773] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2018] [Accepted: 02/25/2019] [Indexed: 05/28/2023]
Abstract
Plants grow and transpire during the night. The aim of the present work was to assess the relative flows of carbon, water and solutes, and the energy involved, in sustaining night-time transpiration and leaf expansive growth under control and salt-stress conditions. Published and unpublished data were used, for barley plants grown in presence of 0.5-1 mM NaCl (control) and 100 mM NaCl. Night-time leaf growth presents a more efficient use of taken-up water compared with day-time growth. This efficiency increases several-fold with salt stress. Night-time transpiration cannot be supported entirely through osmotically driven uptake of water through roots under salt stress. Using a simple three- (root medium/cytosol/vacuole) compartment approach, the energy required to support cell expansion during the night is in the lower percentage region (0.03-5.5%) of the energy available through respiration, under both, control and salt-stress conditions. Use of organic (e.g. hexose equivalents) rather than inorganic (e.g. Na+ , Cl- , K+ ) solutes for generation of osmotic pressure in growing cells, increases the energy demand by orders of magnitude, yet requires only a small portion of carbon assimilated during the day. Night-time transpiration and leaf expansive growth should be considered as a potential acclimation mechanism to salinity.
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Affiliation(s)
- Wieland Fricke
- School of Biology and Environmental Sciences, University College Dublin (UCD), Belfield, Dublin 4, Ireland
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6
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Munns R, Day DA, Fricke W, Watt M, Arsova B, Barkla BJ, Bose J, Byrt CS, Chen ZH, Foster KJ, Gilliham M, Henderson SW, Jenkins CLD, Kronzucker HJ, Miklavcic SJ, Plett D, Roy SJ, Shabala S, Shelden MC, Soole KL, Taylor NL, Tester M, Wege S, Wegner LH, Tyerman SD. Energy costs of salt tolerance in crop plants. THE NEW PHYTOLOGIST 2020; 225:1072-1090. [PMID: 31004496 DOI: 10.1111/nph.15864] [Citation(s) in RCA: 177] [Impact Index Per Article: 44.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Accepted: 03/25/2019] [Indexed: 05/21/2023]
Abstract
Agriculture is expanding into regions that are affected by salinity. This review considers the energetic costs of salinity tolerance in crop plants and provides a framework for a quantitative assessment of costs. Different sources of energy, and modifications of root system architecture that would maximize water vs ion uptake are addressed. Energy requirements for transport of salt (NaCl) to leaf vacuoles for osmotic adjustment could be small if there are no substantial leaks back across plasma membrane and tonoplast in root and leaf. The coupling ratio of the H+ -ATPase also is a critical component. One proposed leak, that of Na+ influx across the plasma membrane through certain aquaporin channels, might be coupled to water flow, thus conserving energy. For the tonoplast, control of two types of cation channels is required for energy efficiency. Transporters controlling the Na+ and Cl- concentrations in mitochondria and chloroplasts are largely unknown and could be a major energy cost. The complexity of the system will require a sophisticated modelling approach to identify critical transporters, apoplastic barriers and root structures. This modelling approach will inform experimentation and allow a quantitative assessment of the energy costs of NaCl tolerance to guide breeding and engineering of molecular components.
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Affiliation(s)
- Rana Munns
- Australian Research Council (ARC) Centre of Excellence in Plant Energy Biology, and School of Agriculture and Environment, The University of Western Australia, Crawley, WA, 6009, Australia
- CSIRO Agriculture and Food, Canberra, ACT, 2601, Australia
| | - David A Day
- College of Science and Engineering, Flinders University, GPO Box 2100, Adelaide, South Australia, 5001, Australia
| | - Wieland Fricke
- School of Biology and Environmental Sciences, University College Dublin (UCD), Dublin, 4, Ireland
| | - Michelle Watt
- Plant Sciences, Institute of Bio and Geosciences, Forschungszentrum Juelich, Helmholtz Association, 52425, Juelich, Germany
| | - Borjana Arsova
- Plant Sciences, Institute of Bio and Geosciences, Forschungszentrum Juelich, Helmholtz Association, 52425, Juelich, Germany
| | - Bronwyn J Barkla
- Southern Cross Plant Science, Southern Cross University, Lismore, NSW, 2481, Australia
| | - Jayakumar Bose
- Australian Research Council (ARC) Centre of Excellence in Plant Energy Biology, School of Agriculture, Food and Wine, University of Adelaide, Glen Osmond, SA, 5064, Australia
| | - Caitlin S Byrt
- Australian Research Council (ARC) Centre of Excellence in Plant Energy Biology, School of Agriculture, Food and Wine, University of Adelaide, Glen Osmond, SA, 5064, Australia
- Research School of Biology, Australian National University, Canberra, ACT, 2600, Australia
| | - Zhong-Hua Chen
- School of Science and Health, Western Sydney University, Penrith, NSW, 2751, Australia
| | - Kylie J Foster
- Phenomics and Bioinformatics Research Centre, School of Information Technology and Mathematical Sciences, University of South Australia, Mawson Lakes, SA, 5095, Australia
| | - Matthew Gilliham
- Australian Research Council (ARC) Centre of Excellence in Plant Energy Biology, School of Agriculture, Food and Wine, University of Adelaide, Glen Osmond, SA, 5064, Australia
| | - Sam W Henderson
- Commonwealth Scientific and Industrial Research Organisation, Agriculture and Food, Urrbrae, SA, 5064, Australia
| | - Colin L D Jenkins
- College of Science and Engineering, Flinders University, GPO Box 2100, Adelaide, South Australia, 5001, Australia
| | - Herbert J Kronzucker
- School of Agriculture and Food, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Melbourne, VIC, 3010, Australia
| | - Stanley J Miklavcic
- Phenomics and Bioinformatics Research Centre, School of Information Technology and Mathematical Sciences, University of South Australia, Mawson Lakes, SA, 5095, Australia
| | - Darren Plett
- School of Agriculture and Food, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Melbourne, VIC, 3010, Australia
| | - Stuart J Roy
- Australian Research Council (ARC) Industrial Transformation Research Hub for Wheat in a Hot and Dry Climate, School of Agriculture, Food and Wine, University of Adelaide, Urrbrae, SA, 5064, Australia
| | - Sergey Shabala
- Tasmanian Institute for Agriculture, University of Tasmania, Private Bag 54, Hobart, Tas., 7001, Australia
- International Centre for Environmental Membrane Biology, Foshan University, Foshan, 528000, China
| | - Megan C Shelden
- Australian Research Council (ARC) Centre of Excellence in Plant Energy Biology, School of Agriculture, Food and Wine, University of Adelaide, Glen Osmond, SA, 5064, Australia
| | - Kathleen L Soole
- College of Science and Engineering, Flinders University, GPO Box 2100, Adelaide, South Australia, 5001, Australia
| | - Nicolas L Taylor
- Australian Research Council (ARC) Centre of Excellence in Plant Energy Biology, School of Molecular Sciences and Institute of Agriculture, The University of Western Australia, Crawley, WA, 6009, Australia
| | - Mark Tester
- Biological and Environmental Sciences & Engineering Division (BESE), King Abdullah University of Science and Technology (KAUST), Thuwal, 23955-6900, Saudi Arabia
| | - Stefanie Wege
- Australian Research Council (ARC) Centre of Excellence in Plant Energy Biology, School of Agriculture, Food and Wine, University of Adelaide, Glen Osmond, SA, 5064, Australia
| | - Lars H Wegner
- Karlsruhe Institute of Technology, Institute for Pulsed Power and Microwave Technology (IHM), D-76344, Eggenstein-Leopoldshafen, Germany
| | - Stephen D Tyerman
- Australian Research Council (ARC) Centre of Excellence in Plant Energy Biology, School of Agriculture, Food and Wine, University of Adelaide, Glen Osmond, SA, 5064, Australia
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Wegner LH, Shabala S. Biochemical pH clamp: the forgotten resource in membrane bioenergetics. THE NEW PHYTOLOGIST 2020; 225:37-47. [PMID: 31393010 DOI: 10.1111/nph.16094] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2019] [Accepted: 08/01/2019] [Indexed: 05/08/2023]
Abstract
Solute uptake and release by plant cells are frequently energized by coupling to H+ influx supported by the proton motive force (pmf). The pmf results from a stable pH difference between the apoplast and the cytosol, with bulk values ranging from 4.9 to 5.8 and from 7.1 to 7.5, respectively, in combination with a negative electrical membrane potential. The P-type H+ ATPases pumping H+ from the cytosol into the apoplast at the expense of ATP hydrolysis are generally viewed as the only pmf source, exclusively linking membrane transport to energy metabolism. However, recent evidence suggests that pump activity may be insufficient to energize transport, particularly under stress conditions. Indeed, cytosolic H+ scavenging and apoplastic H+ generation by metabolism (denoted as 'active' buffering in contrast to the readily exhausted 'passive' matrix buffering) also stabilize the pH gradient. In the cytosol, H+ scavenging is mainly associated with malate decarboxylation catalyzed by malic enzyme, and via the GABA shunt of the tricarboxylic acid (TCA) cycle involving glutamate decarboxylation. In the apoplast, formation of bicarbonate from CO2 , the end-product of respiration, generates H+ at pH ≥ 6. Membrane potential is stabilized by K+ release and/or by anion uptake via ion channels. Finally, thermodynamic aspects of active buffering are discussed.
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Affiliation(s)
- Lars H Wegner
- International Research Centre for Environmental Membrane Biology, Foshan University, Foshan, 528041, China
| | - Sergey Shabala
- International Research Centre for Environmental Membrane Biology, Foshan University, Foshan, 528041, China
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8
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Tyerman SD, Munns R, Fricke W, Arsova B, Barkla BJ, Bose J, Bramley H, Byrt C, Chen Z, Colmer TD, Cuin T, Day DA, Foster KJ, Gilliham M, Henderson SW, Horie T, Jenkins CLD, Kaiser BN, Katsuhara M, Plett D, Miklavcic SJ, Roy SJ, Rubio F, Shabala S, Shelden M, Soole K, Taylor NL, Tester M, Watt M, Wege S, Wegner LH, Wen Z. Energy costs of salinity tolerance in crop plants. THE NEW PHYTOLOGIST 2019; 221:25-29. [PMID: 30488600 DOI: 10.1111/nph.15555] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Affiliation(s)
- Stephen D Tyerman
- Australian Research Council (ARC) Centre of Excellence in Plant Energy Biology, School of Agriculture, Food and Wine, University of Adelaide, Glen Osmond, SA, 5064, Australia
| | - Rana Munns
- ARC Centre of Excellence in Plant Energy Biology, and School of Agriculture and Environment, The University of Western Australia, Crawley, WA, 6009, Australia
- CSIRO Agriculture and Food, Canberra, ACT, 2601, Australia
| | - Wieland Fricke
- School of Biology and Environmental Sciences, University College Dublin (UCD), Dublin, 4, Ireland
| | - Borjana Arsova
- Plant Sciences, Institute of Bio and Geosciences, Forschungszentrum Jülich, Wilhelm-Johnen Strasse, 52425, Jülich, Germany
| | - Bronwyn J Barkla
- Southern Cross Plant Science, Southern Cross University, Lismore, NSW, 2480, Australia
| | - Jayakumar Bose
- Australian Research Council (ARC) Centre of Excellence in Plant Energy Biology, School of Agriculture, Food and Wine, University of Adelaide, Glen Osmond, SA, 5064, Australia
| | - Helen Bramley
- Plant Breeding Institute, Sydney Institute of Agriculture & School of Life and Environmental Sciences, The University of Sydney, Narrabri, NSW, 2390, Australia
| | - Caitlin Byrt
- Australian Research Council (ARC) Centre of Excellence in Plant Energy Biology, School of Agriculture, Food and Wine, University of Adelaide, Glen Osmond, SA, 5064, Australia
| | - Zhonghua Chen
- School of Science and Health, Western Sydney University, Penrith, NSW, 2751, Australia
| | - Timothy D Colmer
- School of Agriculture and Environment, ARC Industrial Transformation Research Hub on Legumes for Sustainable Agriculture, Faculty of Science, The University of Western Australia, Crawley, WA, 6009, Australia
| | - Tracey Cuin
- Tasmanian Institute of Agriculture, University of Tasmania, Hobart, TAS, 7001, Australia
| | - David A Day
- College of Science & Engineering, Flinders University, GPO Box 2100, Adelaide, SA, 5001, Australia
| | - Kylie J Foster
- Phenomics and Bioinformatics Research Centre, University of South Australia, Mawson Lakes, SA, 5095, Australia
| | - Matthew Gilliham
- Australian Research Council (ARC) Centre of Excellence in Plant Energy Biology, School of Agriculture, Food and Wine, University of Adelaide, Glen Osmond, SA, 5064, Australia
| | - Sam W Henderson
- School of Agriculture, Food and Wine, University of Adelaide, Urrbrae, SA, 5064, Australia
- CSIRO Agriculture and Food, Urrbrae, SA, 5064, Australia
| | - Tomoaki Horie
- Division of Applied Biology, Faculty of Textile Science and Technology, Shinshu University, 3-15-1, Tokida, Ueda, Nagano, 386-8567, Japan
| | - Colin L D Jenkins
- College of Sciences and Engineering, Flinders University of South Australia, Bedford Park, SA, 5042, Australia
| | - Brent N Kaiser
- School of Life and Environmental Science, University of Sydney, Camden, NSW, 2570, Australia
| | - Maki Katsuhara
- Institute of Plant Science and Resources, Okayama University, Kurashiki, 7100046, Japan
| | - Darren Plett
- School of Agriculture, Food and Wine, University of Adelaide, Urrbrae, SA, 5064, Australia
- School of Agriculture and Food, The University of Melbourne, Melbourne, VIC, 3010, Australia
| | - Stanley J Miklavcic
- Phenomics and Bioinformatics Research Centre, University of South Australia, Mawson Lakes, SA, 5095, Australia
| | - Stuart J Roy
- School of Agriculture, Food and Wine, University of Adelaide, Urrbrae, SA, 5064, Australia
| | - Francisco Rubio
- Departamento de Nutrición Vegetal, CEBAS-CSIC-Campus de Espinardo, 30100, Murcia, Spain
| | - Sergey Shabala
- College of Science and Engineering, University of Tasmania, Private Bag 54, Hobart, TAS, 7001, Australia
| | - Megan Shelden
- Australian Research Council (ARC) Centre of Excellence in Plant Energy Biology, School of Agriculture, Food and Wine, University of Adelaide, Glen Osmond, SA, 5064, Australia
| | - Kathleen Soole
- College of Sciences and Engineering, Flinders University of South Australia, Bedford Park, SA, 5042, Australia
| | - Nicolas L Taylor
- ARC Centre of Excellence in Plant Energy Biology, School of Molecular Sciences and Institute of Agriculture, The University of Western Australia, Crawley, WA, 6009, Australia
| | - Mark Tester
- Biological and Environmental Sciences & Engineering Division (BESE), King Abdullah University of Science and Technology (KAUST), Thuwal, 23955-6900, Saudi Arabia
| | - Michelle Watt
- Plant Sciences, Institute of Bio and Geosciences, Forschungszentrum Juelich, Helmholtz Association, 52425, Juelich, Germany
| | - Stefanie Wege
- Australian Research Council (ARC) Centre of Excellence in Plant Energy Biology, School of Agriculture, Food and Wine, University of Adelaide, Glen Osmond, SA, 5064, Australia
| | - Lars H Wegner
- Institute for Pulsed Power and Microwave Technology (IHM), Karlsruhe Institute of Technology, D-76344, Eggenstein-Leopoldshafen, Germany
| | - Zhengyu Wen
- School of Life and Environmental Science, University of Sydney, Camden, NSW, 2570, Australia
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9
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Henderson SW, Wege S, Gilliham M. Plant Cation-Chloride Cotransporters (CCC): Evolutionary Origins and Functional Insights. Int J Mol Sci 2018; 19:E492. [PMID: 29415511 PMCID: PMC5855714 DOI: 10.3390/ijms19020492] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Revised: 01/31/2018] [Accepted: 02/01/2018] [Indexed: 01/01/2023] Open
Abstract
Genomes of unicellular and multicellular green algae, mosses, grasses and dicots harbor genes encoding cation-chloride cotransporters (CCC). CCC proteins from the plant kingdom have been comparatively less well investigated than their animal counterparts, but proteins from both plants and animals have been shown to mediate ion fluxes, and are involved in regulation of osmotic processes. In this review, we show that CCC proteins from plants form two distinct phylogenetic clades (CCC1 and CCC2). Some lycophytes and bryophytes possess members from each clade, most land plants only have members of the CCC1 clade, and green algae possess only the CCC2 clade. It is currently unknown whether CCC1 and CCC2 proteins have similar or distinct functions, however they are both more closely related to animal KCC proteins compared to NKCCs. Existing heterologous expression systems that have been used to functionally characterize plant CCC proteins, namely yeast and Xenopus laevis oocytes, have limitations that are discussed. Studies from plants exposed to chemical inhibitors of animal CCC protein function are reviewed for their potential to discern CCC function in planta. Thus far, mutations in plant CCC genes have been evaluated only in two species of angiosperms, and such mutations cause a diverse array of phenotypes-seemingly more than could simply be explained by localized disruption of ion transport alone. We evaluate the putative roles of plant CCC proteins and suggest areas for future investigation.
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Affiliation(s)
- Sam W Henderson
- ARC Centre of Excellence in Plant Energy Biology, School of Agriculture, Food and Wine, University of Adelaide, PMB1, Glen Osmond, SA 5064, Australia.
| | - Stefanie Wege
- ARC Centre of Excellence in Plant Energy Biology, School of Agriculture, Food and Wine, University of Adelaide, PMB1, Glen Osmond, SA 5064, Australia.
| | - Matthew Gilliham
- ARC Centre of Excellence in Plant Energy Biology, School of Agriculture, Food and Wine, University of Adelaide, PMB1, Glen Osmond, SA 5064, Australia.
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10
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Raven JA. Evolution and palaeophysiology of the vascular system and other means of long-distance transport. Philos Trans R Soc Lond B Biol Sci 2018; 373:20160497. [PMID: 29254962 PMCID: PMC5745333 DOI: 10.1098/rstb.2016.0497] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/11/2017] [Indexed: 12/13/2022] Open
Abstract
Photolithotrophic growth on land using atmospheric CO2 inevitably involves H2O vapour loss. Embryophytes greater than or equal to 100 mm tall are homoiohydric and endohydric with mass flow of aqueous solution through the xylem in tracheophytes. Structural details in Rhynie sporophytes enable modelling of the hydraulics of H2O supply to the transpiring surface, and the potential for gas exchange with the Devonian atmosphere. Xylem carrying H2O under tension involves programmed cell death, rigid cell walls and embolism repair; fossils provide little evidence on these functions other than the presence of lignin. The phenylalanine ammonia lyase essential for lignin synthesis came from horizontal gene transfer. Rhynie plants lack endodermes, limiting regulation of the supply of soil nutrients to shoots. The transfer of organic solutes from photosynthetic sites to growing and storage tissues involves mass flow through phloem in extant tracheophytes. Rhynie plants show little evidence of phloem; possible alternatives for transport of organic solutes are discussed. Extant examples of the arbuscular mycorrhizas found in Rhynie plants exchange soil-derived nutrients (especially P) for plant-derived organic matter, involving bidirectional mass flow along the hyphae. The aquatic cyanobacteria and the charalean Palaeonitella at Rhynie also have long-distance (relative to the size of the organism) transport.This article is part of a discussion meeting issue 'The Rhynie cherts: our earliest terrestrial ecosystem revisited'.
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Affiliation(s)
- John A Raven
- Division of Plant Sciences, University of Dundee at the James Hutton Institute, Invergowrie, Dundee DD2 5DA, UK
- School of Biological Sciences, University of Western Australia, 35 Stirling Highway, Crawley, Western Australia 6009, Australia
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11
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Fricke W. Water transport and energy. PLANT, CELL & ENVIRONMENT 2017; 40:977-994. [PMID: 27756100 DOI: 10.1111/pce.12848] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Revised: 10/08/2016] [Accepted: 10/10/2016] [Indexed: 05/10/2023]
Abstract
Water transport in plants occurs along various paths and is driven by gradients in its free energy. It is generally considered that the mode of transport, being either diffusion or bulk flow, is a passive process, although energy may be required to sustain the forces driving water flow. This review aims at putting water flow at the various organisational levels (cell, organ, plant) in the context of the energy that is required to maintain these flows. In addition, the question is addressed (1) whether water can be transported against a difference in its chemical free energy, 'water potential' (Ψ), through, directly or indirectly, active processes; and (2) whether the energy released when water is flowing down a gradient in its energy, for example during day-time transpiration and cell expansive growth, is significant compared to the energy budget of plant and cell. The overall aim of review is not so much to provide a definite 'Yes' and 'No' to these questions, but rather to stimulate discussion and raise awareness that water transport in plants has its real, associated, energy costs and potential energy gains.
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Affiliation(s)
- Wieland Fricke
- School of Biology and Environmental Sciences, University College Dublin (UCD), Belfield, Dublin, 4, Ireland
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12
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Byrt CS, Zhao M, Kourghi M, Bose J, Henderson SW, Qiu J, Gilliham M, Schultz C, Schwarz M, Ramesh SA, Yool A, Tyerman S. Non-selective cation channel activity of aquaporin AtPIP2;1 regulated by Ca 2+ and pH. PLANT, CELL & ENVIRONMENT 2017; 40:802-815. [PMID: 27620834 DOI: 10.1111/pce.12832] [Citation(s) in RCA: 112] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Revised: 09/08/2016] [Accepted: 09/10/2016] [Indexed: 05/20/2023]
Abstract
The aquaporin AtPIP2;1 is an abundant plasma membrane intrinsic protein in Arabidopsis thaliana that is implicated in stomatal closure, and is highly expressed in plasma membranes of root epidermal cells. When expressed in Xenopus laevis oocytes, AtPIP2;1 increased water permeability and induced a non-selective cation conductance mainly associated with Na+ . A mutation in the water pore, G103W, prevented both the ionic conductance and water permeability of PIP2;1. Co-expression of AtPIP2;1 with AtPIP1;2 increased water permeability but abolished the ionic conductance. AtPIP2;2 (93% identical to AtPIP2;1) similarly increased water permeability but not ionic conductance. The ionic conductance was inhibited by the application of extracellular Ca2+ and Cd2+ , with Ca2+ giving a biphasic dose-response with a prominent IC50 of 0.32 mм comparable with a previous report of Ca2+ sensitivity of a non-selective cation channel (NSCC) in Arabidopsis root protoplasts. Low external pH also inhibited ionic conductance (IC50 pH 6.8). Xenopus oocytes and Saccharomyces cerevisiae expressing AtPIP2;1 accumulated more Na+ than controls. Establishing whether AtPIP2;1 has dual ion and water permeability in planta will be important in understanding the roles of this aquaporin and if AtPIP2;1 is a candidate for a previously reported NSCC responsible for Ca2+ and pH sensitive Na+ entry into roots.
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Affiliation(s)
- Caitlin S Byrt
- Australian Research Council Centre of Excellence in Plant Energy Biology, Waite Research Institute and School of Agriculture, Food and Wine, The University of Adelaide, Glen Osmond, South Australia, 5064, Australia
| | - Manchun Zhao
- Australian Research Council Centre of Excellence in Plant Energy Biology, Waite Research Institute and School of Agriculture, Food and Wine, The University of Adelaide, Glen Osmond, South Australia, 5064, Australia
| | - Mohamad Kourghi
- Discipline of Physiology, School of Medicine, University of Adelaide, South Australia, 5005, Australia
| | - Jayakumar Bose
- Australian Research Council Centre of Excellence in Plant Energy Biology, Waite Research Institute and School of Agriculture, Food and Wine, The University of Adelaide, Glen Osmond, South Australia, 5064, Australia
| | - Sam W Henderson
- Australian Research Council Centre of Excellence in Plant Energy Biology, Waite Research Institute and School of Agriculture, Food and Wine, The University of Adelaide, Glen Osmond, South Australia, 5064, Australia
| | - Jiaen Qiu
- Australian Research Council Centre of Excellence in Plant Energy Biology, Waite Research Institute and School of Agriculture, Food and Wine, The University of Adelaide, Glen Osmond, South Australia, 5064, Australia
| | - Matthew Gilliham
- Australian Research Council Centre of Excellence in Plant Energy Biology, Waite Research Institute and School of Agriculture, Food and Wine, The University of Adelaide, Glen Osmond, South Australia, 5064, Australia
| | - Carolyn Schultz
- Waite Research Institute and School of Agriculture, Food and Wine, The University of Adelaide, Glen Osmond, South Australia, 5064, Australia
| | - Manuel Schwarz
- Australian Research Council Centre of Excellence in Plant Energy Biology, Waite Research Institute and School of Agriculture, Food and Wine, The University of Adelaide, Glen Osmond, South Australia, 5064, Australia
| | - Sunita A Ramesh
- Australian Research Council Centre of Excellence in Plant Energy Biology, Waite Research Institute and School of Agriculture, Food and Wine, The University of Adelaide, Glen Osmond, South Australia, 5064, Australia
| | - Andrea Yool
- Discipline of Physiology, School of Medicine, University of Adelaide, South Australia, 5005, Australia
| | - Steve Tyerman
- Australian Research Council Centre of Excellence in Plant Energy Biology, Waite Research Institute and School of Agriculture, Food and Wine, The University of Adelaide, Glen Osmond, South Australia, 5064, Australia
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13
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Bentrup FW. Water ascent in trees and lianas: the cohesion-tension theory revisited in the wake of Otto Renner. PROTOPLASMA 2017; 254:627-633. [PMID: 27491484 PMCID: PMC5591614 DOI: 10.1007/s00709-016-1009-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2016] [Accepted: 07/21/2016] [Indexed: 05/26/2023]
Abstract
The cohesion-tension theory of water ascent (C-T) has been challenged over the past decades by a large body of experimental evidence obtained by means of several minimum or non-invasive techniques. The evidence strongly suggests that land plants acquire water through interplay of several mechanisms covered by the multi-force theory of (U. Zimmermann et al. New Phytologist 162: 575-615, 2004). The diversity of mechanisms includes, for instance, water acquisition by inverse transpiration and thermodynamically uphill transmembrane water secretion by cation-chloride cotransporters (L.H. Wegner, Progress in Botany 76:109-141, 2014). This whole plant perspective was opened by Otto Renner at the beginning of the last century who supported experimentally the strictly xylem-bound C-T mechanism, yet anticipated that the water ascent involves both the xylem conduit and parenchyma tissues. The survey also illustrates the known paradigm that new techniques generate new insights, as well as a paradigm experienced by Max Planck that a new scientific idea is not welcomed by the community instantly.
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14
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Wegner LH. A pump/leak model of growth: the biophysics of cell elongation in higher plants revisited. FUNCTIONAL PLANT BIOLOGY : FPB 2017; 44:185-197. [PMID: 32480556 DOI: 10.1071/fp16184] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2016] [Accepted: 09/08/2016] [Indexed: 06/11/2023]
Abstract
Current concepts of growth hydraulics in higher plants are critically revisited, and it is concluded that they partly fail to interpret the experimental data adequately, particularly in the case of hydroponics-grown roots. Theoretical considerations indicate that the growth rate in roots is controlled by the extensibility of the cell wall, excluding water availability (i.e. hydraulic conductance) as a major constraint. This is supported by the findings that the growth rate does not scale with turgor, and that no radial nor axial water potential gradients have been observed in the root elongation zone. Nevertheless, a water potential deficit ranging from -0.2 to -0.6MPa has repeatedly been reported for growing cells that by far exceeds the shallow trans-membrane water potential difference required for the uptake of growth water. Unexpectedly, growth was also shown to depend on the hydraulic conductance (LP) of the plasma membrane of root cells, even though LP should generally be too large to have an impact on growth. For leaves, similar observations have been reported, but the interpretation of the data is less straightforward. Inconsistencies associated with the current model of growth hydraulics prompt the author to suggest a revised model that comprises, in addition to a passive mechanism of water transport across the plasma membrane of growing cells mediated by aquaporins ('leak') a secondary active water transport ('pump'), in analogy to a mechanism previously demonstrated for mammalian epithelia and postulated for xylem parenchyma cells in roots. Water is hypothesised to be secreted against a trans-membrane water potential difference by cotransport with solutes (salts, sugars, and/or amino acids), taking advantage of the free energy released by this transport step. The solute concentration gradient is supposed to be maintained by a subsequent retrieval of the solutes from the apoplast and back-transport at the expense of metabolic energy. Water secretion tends to reduce the turgor pressure and retards growth, but turgor and, in turn, growth can be upregulated very rapidly independent from any adjustment in the osmolyte deposition rate by increasing LP and/or reducing secondary active water transport, e.g. when the root is exposed to mild osmotic stress, as confirmed by experimental studies.
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Affiliation(s)
- Lars H Wegner
- Karlsruhe Institute of Technology, Institute for Pulsed Power and Microwave Technology (IHM), Campus North, Building 630, Hermann v. Helmholtz Platz 1, 76344 Eggenstein-Leopoldshafen, Germany. Email
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15
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H. Wegner L. Cotransport of water and solutes in plant membranes: The molecular basis, and physiological functions. AIMS BIOPHYSICS 2017. [DOI: 10.3934/biophy.2017.2.192] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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16
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Zhao L, Wang L, Cernusak LA, Liu X, Xiao H, Zhou M, Zhang S. Significant Difference in Hydrogen Isotope Composition Between Xylem and Tissue Water in Populus Euphratica. PLANT, CELL & ENVIRONMENT 2016; 39:1848-1857. [PMID: 27061571 DOI: 10.1111/pce.12753] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2015] [Revised: 04/03/2016] [Accepted: 04/04/2016] [Indexed: 06/05/2023]
Abstract
Deuterium depletions between stem water and source water have been observed in coastal halophyte plants and in multiple species under greenhouse conditions. However, the location(s) of the isotope fractionation is not clear yet and it is uncertain whether deuterium fractionation appears in other natural environments. In this study, through two extensive field campaigns utilizing a common dryland riparian tree species Populus euphratica Oliv., we showed that no significant δ(18) O differences were found between water source and various plant components, in accord with previous studies. We also found that no deuterium fractionation occurred during P. euphratica water uptake by comparing the deuterium composition (δD) of groundwater and xylem sap. However, remarkable δD differences (up to 26.4‰) between xylem sap and twig water, root water and core water provided direct evidence that deuterium fractionation occurred between xylem sap and root or stem tissue water. This study indicates that deuterium fractionation could be a common phenomenon in drylands, which has important implications in plant water source identification, palaeoclimate reconstruction based on wood cellulose and evapotranspiration partitioning using δD of stem water.
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Affiliation(s)
- Liangju Zhao
- College of Urban and Environmental Sciences, Northwest University, Xi'an, 710069, China
- Key Laboratory of Ecohydrology and Integrated River Basin Science, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou, 730000, China
| | - Lixin Wang
- Department of Earth Sciences, Indiana University-Purdue University Indianapolis (IUPUI), Indianapolis, IN, 46202, USA
| | - Lucas A Cernusak
- College of Marine and Environmental Sciences, James Cook University, Cairns, Queensland, Australia
| | - Xiaohong Liu
- State Key Laboratory of Cryospheric Sciences, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou, 730000, China
| | - Honglang Xiao
- Key Laboratory of Ecohydrology and Integrated River Basin Science, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou, 730000, China
| | - Maoxian Zhou
- School of Agriculture and Forestry Economics and Management, Lanzhou University of Finance and Economics, Lanzhou, 730101, China
| | - Shiqiang Zhang
- College of Urban and Environmental Sciences, Northwest University, Xi'an, 710069, China
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Paudel I, Cohen S, Shaviv A, Bar-Tal A, Bernstein N, Heuer B, Ephrath J. Impact of treated wastewater on growth, respiration and hydraulic conductivity of citrus root systems in light and heavy soils. TREE PHYSIOLOGY 2016; 36:770-85. [PMID: 27022106 DOI: 10.1093/treephys/tpw013] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2015] [Accepted: 01/27/2016] [Indexed: 05/17/2023]
Abstract
Roots interact with soil properties and irrigation water quality leading to changes in root growth, structure and function. We studied these interactions in an orchard and in lysimeters with clay and sandy loam soils. Minirhizotron imaging and manual sampling showed that root growth was three times lower in the clay relative to sandy loam soil. Treated wastewater (TWW) led to a large reduction in root growth with clay (45-55%) but not with sandy loam soil (<20%). Treated wastewater increased salt uptake, membrane leakage and proline content, and decreased root viability, carbohydrate content and osmotic potentials in the fine roots, especially in clay. These results provide evidence that TWW challenges and damages the root system. The phenology and physiology of root orders were studied in lysimeters. Soil type influenced diameter, specific root area, tissue density and cortex area similarly in all root orders, while TWW influenced these only in clay soil. Respiration rates were similar in both soils, and root hydraulic conductivity was severely reduced in clay soil. Treated wastewater increased respiration rate and reduced hydraulic conductivity of all root orders in clay but only of the lower root orders in sandy loam soil. Loss of hydraulic conductivity increased with root order in clay and clay irrigated with TWW. Respiration and hydraulic properties of all root orders were significantly affected by sodium-amended TWW in sandy loam soil. These changes in root order morphology, anatomy, physiology and hydraulic properties indicate rapid and major modifications of root systems in response to differences in soil type and water quality.
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Affiliation(s)
- Indira Paudel
- Institute of Soil, Water and Environmental Sciences, ARO Volcani Center, Bet Dagan 50250, Israel The Robert H. Smith Faculty of Food Agriculture and Environment, The Hebrew University of Jerusalem, Rehovot 76100, Israel
| | - Shabtai Cohen
- Institute of Soil, Water and Environmental Sciences, ARO Volcani Center, Bet Dagan 50250, Israel
| | - Avi Shaviv
- Department of Environmental, Water and Agricultural Engineering, Faculty of Civil and Environmental Engineering, Technion-Israel Institute of Technology, Haifa 32000, Israel
| | - Asher Bar-Tal
- Institute of Soil, Water and Environmental Sciences, ARO Volcani Center, Bet Dagan 50250, Israel
| | - Nirit Bernstein
- Institute of Soil, Water and Environmental Sciences, ARO Volcani Center, Bet Dagan 50250, Israel
| | - Bruria Heuer
- Institute of Soil, Water and Environmental Sciences, ARO Volcani Center, Bet Dagan 50250, Israel
| | - Jhonathan Ephrath
- Jacob Blaustein Institutes for Desert Research, French Associates Institute for Agriculture and Biotechnology of Drylands, Ben-Gurion University of the Negev, Sde Boqer 849900, Israel
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