© 2007 The Author(s).
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RESEARCH PAPER |
Compatible solute accumulation and stress-mitigating effects in barley genotypes contrasting in their salt tolerance
1School of Agricultural Science, Private Bag 54, University of Tasmania, Hobart, TAS 7001, Australia
2Tasmanian Institute of Agricultural Research, University of Tasmania, Kings Meadows, TAS 7249, Australia
3School of Land, Crop and Food Sciences, The University of Queensland, St Lucia, QLD 4072, Australia
4Department of Natural Resources and Water, Block-B, 80 Meiers Rd, Indooroopilly, QLD 4068, Australia
* To whom correspondence should be addressed. E-mail: Sergey.Shabala{at}utas.edu.au
The accumulation of compatible solutes is often regarded as a basic strategy for the protection and survival of plants under abiotic stress conditions, including both salinity and oxidative stress. In this work, a possible causal link between the ability of contrasting barley genotypes to accumulate/synthesize compatible solutes and their salinity stress tolerance was investigated. The impact of H2O2 (one of the components of salt stress) on K+ flux (a measure of stress ‘severity’) and the mitigating effects of glycine betaine and proline on NaCl-induced K+ efflux were found to be significantly higher in salt-sensitive barley genotypes. At the same time, a 2-fold higher accumulation of leaf and root proline and leaf glycine betaine was found in salt-sensitive cultivars. The total amino acid content was also less affected by salinity in salt-tolerant cultivars. In these, potassium was found to be the main contributor to cytoplasmic osmolality, while in salt-sensitive genotypes, glycine betaine and proline contributed substantially to cell osmolality, compensating for reduced cytosolic K+. Significant negative correlations (r= –0.89 and –0.94) were observed between Na+-induced K+ efflux (an indicator of salt tolerance) and leaf glycine betaine and proline. These results indicate that hyperaccumulation of known major compatible solutes in barley does not appear to play a major role in salt-tolerance, but rather, may be a symptom of salt-susceptibility.
Key words: Glycine betaine, Hordeum vulgare L., potassium flux, proline, reactive oxygen species, salinity
Received 10 August 2007; Revised 21 October 2007 Accepted 23 October 2007
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