Multiple traits associated with salt tolerance in lucerne: revealing the underlying cellular mechanisms
Christiane F. Smethurst A , Kieren Rix A , Trevor Garnett B , Geoff Auricht B , Antoine Bayart C , Peter Lane A , Stephen J. Wilson A and Sergey Shabala A DA School of Agricultural Science, University of Tasmania, Private Bag 54, Hobart, Tas. 7001, Australia.
B South Australian Research and Development Institute, Waite Campus, GPO Box 397, Adelaide, SA 5001, Australia.
C Institute Polytechnique LaSalle Beauvais, BP 30313-60026 Beauvais Cedex, France.
D Corresponding author. Email: sergey.shabala@utas.edu.au
Functional Plant Biology 35(7) 640-650 https://doi.org/10.1071/FP08030
Submitted: 19 February 2008 Accepted: 24 May 2008 Published: 21 August 2008
Abstract
Salinity tolerance is a complex trait inferring the orchestrated regulation of a large number of physiological and biochemical processes at various levels of plant structural organisation. It remains to be answered which mechanisms and processes are crucial for salt tolerance in lucerne (Medicago sativa L.). In this study, salinity effects on plant growth characteristics, pigment and nutrient composition, PSII photochemistry, leaf sap osmolality, changes in anatomical and electrophysiological characteristics of leaf mesophyll, and net ion fluxes in roots of several lucerne genotypes were analysed. Salinity levels ranged from 40 to ~200 mm NaCl, and were applied to either 2-month-old plants or to germinating seedlings for a period of between 4 and 12 weeks in a series of hydroponic, pot and field experiments. Overall, the results suggest that different lucerne genotypes employ at least two different mechanisms for salt tolerance. Sodium exclusion appeared to be the mechanism employed by at least one of the tolerant genotypes (Ameristand 801S). This cultivar had the lowest leaf thickness, as well as the lowest concentration of Na+ in the leaf tissue. The other tolerant genotype, L33, had much thicker leaves and almost twice the leaf Na+ concentration of Ameristand. Both cultivars showed much less depolarisation of leaf membrane potential than the sensitive cultivars and, thus, had better K+ retention ability in both root and leaf tissues. The implications of the above measurements for screening lucerne germplasm for salt tolerance are discussed.
Additional keywords: adaptation, alfalfa, compartmentation, depolarisation, exclusion, ion fluxes, Medicago sativa, membrane transport, potassium homeostasis, salinity, sodium, succulency.
Acknowledgements
This work was supported by an ACIAR grant to G.A. and S.S. The authors thank Phil Andrews for looking after the smooth operation of the glasshouse, Dr Greg Jordan for his help with microtome sectioning, and Dr Greg Sweeney for providing lucerne seeds.
Al-Khatib M,
McNeilly T, Collins JC
(1993) The potential of selection and breeding for improved salt tolerance in lucerne (Medicago sativa L.). Euphytica 65, 43–51.
| Crossref | GoogleScholarGoogle Scholar |
Babourina O,
Leonova T,
Shabala S, Newman I
(2000) Effect of sudden salt stress on ion fluxes in intact wheat suspension cells. Annals of Botany 85, 759–767.
| Crossref | GoogleScholarGoogle Scholar |
Baxter DF,
Kirk M,
Garcia AF,
Raimondi A,
Holmqvist MH,
Flint K,
Bojanic D,
Distefano PS,
Curtis R, Xie Y
(2002) A novel membrane potential-sensitive fluorescent dye improves cell-based assays for ion channels. Journal of Biomolecular Screening 7, 79–85.
| Crossref | GoogleScholarGoogle Scholar | PubMed |
Belkodja R,
Morales F,
Abadia A,
Gomez-Aparisi J, Abadia J
(1994) Chlorophyll fluorescence as a possible tool for salinity tolerance screening in barley (Hordeum vulgare L.). Plant Physiology 104, 667–673.
| PubMed |
Björkman O, Demmig B
(1987) Photon yield of O2 evolution and chlorophyll fluorescence characteristics at 77 K among plants of diverse origins. Planta 170, 489–504.
| Crossref | GoogleScholarGoogle Scholar |
Blumwald E,
Aharon GS, Apse MP
(2000) Sodium transport in plant cells. Biochimica et Biophysica Acta-Biomembranes 1465, 140–151.
| Crossref | GoogleScholarGoogle Scholar |
Bohnert HJ, Shen B
(1998) Transformation and compatible solutes. Scientia Horticulturae 78, 237–260.
| Crossref | GoogleScholarGoogle Scholar |
Carden DE,
Diamond D, Miller AJ
(2001) An improved Na+-selective microelectrode for intracellular measurements in plant cells. Journal of Experimental Botany 52, 1353–1359.
| Crossref | GoogleScholarGoogle Scholar | PubMed |
Carden DE,
Walker DJ,
Flowers TJ, Miller AJ
(2003) Single-cell measurements of the contributions of cytosolic Na+ and K+ to salt tolerance. Plant Physiology 131, 676–683.
| Crossref | GoogleScholarGoogle Scholar | PubMed |
Chaudhary MT,
Wainwright SJ, Merrett MJ
(1996) Comparative NaCl tolerance of lucerne plants regenerated from salt-selected suspension cultures. Plant Science 114, 221–232.
| Crossref | GoogleScholarGoogle Scholar |
Chen Z,
Newman I,
Zhou M,
Mendham N,
Zhang G, Shabala S
(2005) Screening plants for salt tolerance by measuring K+ flux: a case study for barley. Plant, Cell & Environment 28, 1230–1246.
| Crossref | GoogleScholarGoogle Scholar |
Chen ZH,
Pottosin II,
Cuin TA,
Fuglsang AT, Tester M , et al.
(2007a) Root plasma membrane transporters controlling K+/Na+ homeostasis in salt-stressed barley. Plant Physiology 145, 1714–1725.
| Crossref | GoogleScholarGoogle Scholar | PubMed |
Chen ZH,
Zhou MX,
Newman IA,
Mendham NJ,
Zhang GP, Shabala S
(2007b) Potassium and sodium relations in salinised barley tissues as a basis of differential salt tolerance. Functional Plant Biology 34, 150–162.
| Crossref | GoogleScholarGoogle Scholar |
Chow WS,
Ball MC, Anderson JM
(1990) Growth and photosynthetic responses of spinach to salinity – Implications of K+ nutrition for salt tolerance. Australian Journal of Plant Physiology 17, 563–578.
Cuin TA,
Miller AJ,
Laurie SA, Leigh RA
(2003) Potassium activities in cell compartments of salt-grown barley leaves. Journal of Experimental Botany 54, 657–661.
| Crossref | GoogleScholarGoogle Scholar | PubMed |
Delfine S,
Alvino A,
Zacchini M, Loreto F
(1998) Consequences of salt stress on conductance to CO2 diffusion, Rubisco characteristics and anatomy of spinach leaves. Australian Journal of Plant Physiology 25, 395–402.
Flowers TJ
(2004) Improving crop salt tolerance. Journal of Experimental Botany 55, 307–319.
| Crossref | GoogleScholarGoogle Scholar | PubMed |
Flowers TJ, Hajibagheri MA
(2001) Salinity tolerance in Hordeum vulgare: ion concentrations in root cells of cultivars differing in salt tolerance. Plant and Soil 231, 1–9.
| Crossref | GoogleScholarGoogle Scholar |
Flowers TJ, Yeo AR
(1995) Breeding for salinity resistance in crop plants: where next? Australian Journal of Plant Physiology 22, 875–884.
Gorham J,
Wyn Jones RG, McDonnell E
(1985) Some mechanisms of salt tolerance in crop plants. Plant and Soil 89, 15–40.
| Crossref | GoogleScholarGoogle Scholar |
Jimenez MS,
Gonzalez-Rodriguez AM,
Morales D,
Cid MC,
Socorro AR, Caballero M
(1997) Evaluation of chlorophyll fluorescence as a tool for stress detection in roses. Photosynthetica 33, 291–301.
| Crossref | GoogleScholarGoogle Scholar |
Karley AJ,
Leigh RA, Sanders D
(2000) Differential ion accumulation and ion fluxes in the mesophyll and epidermis of barley. Plant Physiology 122, 835–844.
| Crossref | GoogleScholarGoogle Scholar | PubMed |
Leigh RA
(2001) Potassium homeostasis and membrane transport. Journal of Plant Nutrition and Soil Science 164, 193–198.
| Crossref | GoogleScholarGoogle Scholar |
Ma H-C,
Fung L,
Wang S-S,
Altman A, Hüttermann A
(1997) Photosynthetic response of Populus euphratica to salt stress. Forest Ecology and Management 93, 55–61.
| Crossref | GoogleScholarGoogle Scholar |
Maathuis FJM, Amtmann A
(1999) K+ nutrition and Na+ toxicity: the basis of cellular K+/Na+ ratios. Annals of Botany 84, 123–133.
| Crossref | GoogleScholarGoogle Scholar |
Maathuis FJM, Sanders D
(1999) Plasma membrane transport in context – making sense out of complexity. Current Opinion in Plant Biology 2, 236–243.
| Crossref | GoogleScholarGoogle Scholar | PubMed |
Maathuis FJM,
Verlin D,
Smith FA,
Sanders D,
Fernandez JA, Walker NA
(1996) The physiological relevance of Na+-coupled K+-transport. Plant Physiology 112, 1609–1616.
| PubMed |
Maser P,
Gierth M, Schroeder JI
(2002) Molecular mechanisms of potassium and sodium uptake in plants. Plant and Soil 247, 43–54.
| Crossref | GoogleScholarGoogle Scholar |
Mohammadi H,
Poustini K, Ahmadi A
(2008) Root nitrogen remobilisation and ion status of two alfalfa (Medicago sativa L.) cultivars in response to salinity stress. Journal Agronomy & Crop Science 194, 126–134.
| Crossref | GoogleScholarGoogle Scholar |
Munns R
(2002) Comparative physiology of salt and water stress. Plant, Cell & Environment 25, 239–250.
| Crossref | GoogleScholarGoogle Scholar | PubMed |
Munns R
(2005) Genes and salt tolerance: bringing them together. New Phytologist 167, 645–663.
| Crossref | GoogleScholarGoogle Scholar | PubMed |
Munns R, James RA
(2003) Screening methods for salinity tolerance: a case study with tetraploid wheat. Plant and Soil 253, 201–218.
| Crossref | GoogleScholarGoogle Scholar |
Newman IA
(2001) Ion transport in roots: measurement of fluxes using ion-selective microelectrodes to characterize transporter function. Plant, Cell & Environment 24, 1–14.
| Crossref | GoogleScholarGoogle Scholar | PubMed |
Pineros MA, Kochian LV
(2003) Differences in whole-cell and single-channel ion currents across the plasma membrane of mesophyll cells from two closely related Thlaspi species. Plant Physiology 131, 583–594.
| Crossref | GoogleScholarGoogle Scholar | PubMed |
Rivelli AR,
James RA,
Munns R, Condon AG
(2002) Effect of salinity on water relations and growth of wheat genotypes with contrasting sodium uptake. Functional Plant Biology 29, 1065–1074.
| Crossref | GoogleScholarGoogle Scholar |
Rogers ME
(2001) The effect of saline irrigation on lucerne production: shoot and root growth, ion relations and flowering incidence in six cultivars grown in Northern Victoria, Australia. Irrigation Science 20, 55–64.
| Crossref | GoogleScholarGoogle Scholar |
Rogers ME, Noble CL
(1992) Variation in growth and ion accumulation between two selected populations of Trifolium repens L. differing in salt tolerance. Plant and Soil 146, 131–136.
| Crossref | GoogleScholarGoogle Scholar |
Rogers ME,
Grieve CM, Shannon MC
(2003) Plant growth and ion relations in lucerne (Medicago sativa L.) in response to the combined effects of NaCl and P. Plant and Soil 253, 187–194.
| Crossref | GoogleScholarGoogle Scholar |
Shabala S
(2000) Ionic and osmotic components of salt stress specifically modulate net ion fluxes from bean leaf mesophyll. Plant, Cell & Environment 23, 825–837.
| Crossref | GoogleScholarGoogle Scholar |
Shabala S
(2003) Regulation of potassium transport in leaves: from molecular to tissue level. Annals of Botany 92, 627–634.
| Crossref | GoogleScholarGoogle Scholar | PubMed |
Shabala S, Cuin TA
(2008) Potassium transport and plant salt tolerance. Physiologia Plantarum (in press). ,
Shabala S, Lew RR
(2002) Turgor regulation in osmotically stressed Arabidopsis epidermal root cells. Direct support for the role of inorganic ion uptake as revealed by concurrent flux and cell turgor measurements. Plant Physiology 129, 290–299.
| Crossref | GoogleScholarGoogle Scholar | PubMed |
Shabala S, Newman IA
(1999) Light-induced changes in hydrogen, calcium, potassium, and chloride ion fluxes and concentrations from mesophyll and epidermal tissues of bean leaves. Understanding the ionic basis of light-induced bioelectrogenisis. Plant Physiology 119, 1115–1124.
| Crossref | GoogleScholarGoogle Scholar | PubMed |
Shabala S,
Newman IA, Morris J
(1997) Oscillations in H+ and Ca2+ ion fluxes around the elongation region of corn roots and effects of external pH. Plant Physiology 113, 111–118.
| PubMed |
Shabala S,
Shabala SI,
Martynenko AI,
Babourina O, Newman IA
(1998) Salinity effect on bioelectric activity, growth, Na+ accumulation and chlorophyll fluorescence of maize leaves: a comparative survey and prospects for screening. Australian Journal of Plant Physiology 25, 609–616.
Shabala S,
Shabala L, Van Volkenburgh E
(2003) Effect of calcium on root development and root ion fluxes in salinised barley seedlings. Functional Plant Biology 30, 507–514.
| Crossref | GoogleScholarGoogle Scholar |
Shabala S,
Demidchik V,
Shabala L,
Cuin TA,
Smith SJ,
Miller AJ,
Davies JM, Newman IA
(2006) Extracellular Ca2+ ameliorates NaCl-induced K+ loss from Arabidopsis root and leaf cells by controlling plasma membrane K+ permeable channels. Plant Physiology 141, 1653–1665.
| Crossref | GoogleScholarGoogle Scholar | PubMed |
Smethurst CF, Shabala S
(2003) Screening methods for waterlogging tolerance in lucerne: comparative analysis of waterlogging effects on chlorophyll fluorescence, photosynthesis, biomass and chlorophyll content. Functional Plant Biology 30, 335–343.
| Crossref | GoogleScholarGoogle Scholar |
Smethurst CF,
Garnett T, Shabala S
(2005) Nutritional and chlorophyll fluorescence responses of lucerne (Medicago sativa) to waterlogging and subsequent recovery. Plant and Soil 270, 31–45.
| Crossref | GoogleScholarGoogle Scholar |
Tester M, Davenport R
(2003) Na+ tolerance and Na+ transport in higher plants. Annals of Botany 91, 503–527.
| Crossref | GoogleScholarGoogle Scholar | PubMed |
Wegner LH, De Boer AH
(1999) Activation kinetics of the K+ outward rectifying conductance (KORC) in xylem parenchyma cells from barley roots. Journal of Membrane Biology 170, 103–119.
| Crossref | GoogleScholarGoogle Scholar | PubMed |
Wu Y,
Sharp RE,
Durachko DM, Cosgrove DJ
(1996) Growth maintenance of the maize primary root at low water potentials involves increases in cell-wall extension properties, expansin activity, and wall susceptibility to expansins. Plant Physiology 111, 765–772.
| PubMed |
Zhang HX, Blumwald E
(2001) Transgenic salt-tolerant tomato plants accumulate salt in foliage but not in fruit. Nature Biotechnology 19, 765–768.
| Crossref | GoogleScholarGoogle Scholar | PubMed |
Zhu JK
(2001) Plant salt tolerance. Trends in Plant Science 6, 66–71.
| Crossref | GoogleScholarGoogle Scholar | PubMed |
Zhu JK,
Liu JP, Xiong LM
(1998) Genetic analysis of salt tolerance in Arabidopsis – evidence for a critical role of potassium nutrition. The Plant Cell 10, 1181–1191.
| Crossref | GoogleScholarGoogle Scholar | PubMed |
