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Flowers TJ, Munns R, Colmer TD. Sodium chloride toxicity and the cellular basis of salt tolerance in halophytes. ANNALS OF BOTANY 2015; 115:419-31. [PMID: 25466549 PMCID: PMC4332607 DOI: 10.1093/aob/mcu217] [Citation(s) in RCA: 275] [Impact Index Per Article: 30.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2014] [Revised: 08/01/2014] [Accepted: 09/19/2014] [Indexed: 05/18/2023]
Abstract
BACKGROUND Halophytes are the flora of saline soils. They adjust osmotically to soil salinity by accumulating ions and sequestering the vast majority of these (generally Na(+) and Cl(-)) in vacuoles, while in the cytoplasm organic solutes are accumulated to prevent adverse effects on metabolism. At high salinities, however, growth is inhibited. Possible causes are: toxicity to metabolism of Na(+) and/or Cl(-) in the cytoplasm; insufficient osmotic adjustment resulting in reduced net photosynthesis because of stomatal closure; reduced turgor for expansion growth; adverse cellular water relations if ions build up in the apoplast (cell walls) of leaves; diversion of energy needed to maintain solute homeostasis; sub-optimal levels of K(+) (or other mineral nutrients) required for maintaining enzyme activities; possible damage from reactive oxygen species; or changes in hormonal concentrations. SCOPE This review discusses the evidence for Na(+) and Cl(-) toxicity and the concept of tissue tolerance in relation to halophytes. CONCLUSIONS The data reviewed here suggest that halophytes tolerate cytoplasmic Na(+) and Cl(-) concentrations of 100-200 mm, but whether these ions ever reach toxic concentrations that inhibit metabolism in the cytoplasm or cause death is unknown. Measurements of ion concentrations in the cytosol of various cell types for contrasting species and growth conditions are needed. Future work should also focus on the properties of the tonoplast that enable ion accumulation and prevent ion leakage, such as the special properties of ion transporters and of the lipids that determine membrane permeability.
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Affiliation(s)
- Timothy J Flowers
- School of Plant Biology and ARC Centre of Excellence in Plant Energy Biology, The University of Western Australia, 35 Stirling Highway, Crawley, WA, 6009, Australia, CSIRO Agriculture, GPO Box 1600, Canberra, ACT, 2601, Australia and School of Life Sciences, University of Sussex, Falmer, Brighton BN7 1BD, UK School of Plant Biology and ARC Centre of Excellence in Plant Energy Biology, The University of Western Australia, 35 Stirling Highway, Crawley, WA, 6009, Australia, CSIRO Agriculture, GPO Box 1600, Canberra, ACT, 2601, Australia and School of Life Sciences, University of Sussex, Falmer, Brighton BN7 1BD, UK
| | - Rana Munns
- School of Plant Biology and ARC Centre of Excellence in Plant Energy Biology, The University of Western Australia, 35 Stirling Highway, Crawley, WA, 6009, Australia, CSIRO Agriculture, GPO Box 1600, Canberra, ACT, 2601, Australia and School of Life Sciences, University of Sussex, Falmer, Brighton BN7 1BD, UK School of Plant Biology and ARC Centre of Excellence in Plant Energy Biology, The University of Western Australia, 35 Stirling Highway, Crawley, WA, 6009, Australia, CSIRO Agriculture, GPO Box 1600, Canberra, ACT, 2601, Australia and School of Life Sciences, University of Sussex, Falmer, Brighton BN7 1BD, UK School of Plant Biology and ARC Centre of Excellence in Plant Energy Biology, The University of Western Australia, 35 Stirling Highway, Crawley, WA, 6009, Australia, CSIRO Agriculture, GPO Box 1600, Canberra, ACT, 2601, Australia and School of Life Sciences, University of Sussex, Falmer, Brighton BN7 1BD, UK
| | - Timothy D Colmer
- School of Plant Biology and ARC Centre of Excellence in Plant Energy Biology, The University of Western Australia, 35 Stirling Highway, Crawley, WA, 6009, Australia, CSIRO Agriculture, GPO Box 1600, Canberra, ACT, 2601, Australia and School of Life Sciences, University of Sussex, Falmer, Brighton BN7 1BD, UK
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Preston C, Critchley C. Interaction of electron acceptors with thylakoids from halophytic and non-halophytic species. PHOTOSYNTHESIS RESEARCH 1988; 16:187-202. [PMID: 24429526 DOI: 10.1007/bf00028838] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/1987] [Accepted: 11/26/1987] [Indexed: 06/03/2023]
Abstract
Thylakoid membranes isolated from halophytic species showed differences in their interactions with ionic and lipophilic electron acceptors when compared to thylakoids from non-halophytes. FeCN was considerably less efficient as electron acceptor with halophyte thylakoids, supporting much lower rates of O2 evolution and having a lower affinity. FeCN accepted electrons at a different, DMMIB insensitive, site with these thylakoids. 1,4-Benzo-quinones with less positive midpoint potentials were less effective in accepting electrons from halophyte thylakoids compared to nonhalophyte thylakoids, also reflected in lower rates of O2 evolution and lower affinity. Considering the lipolphilic nature and the fact that there was no apparent change in the site donating electrons to the quinones, an alteration in the midpoint potential of this site by about +100mV is postulated for the halophyte thylakoids.
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Affiliation(s)
- C Preston
- Botany Department, The Faculties, Australian National University, GPO Box 4, 2601, Canberra, ACT, Australia
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