Mechanisms of Salinity Tolerance Rana Munns 1 and Mark Tester 2 1 CSIRO Plant Industry, Canberra, ACT, Australia; email: rana.munns@csiro.au 2 Australian Center for Plant Functional Genomics and University of Adelaide, SA, Australia; email: mark.tester@acpfg.com.au Annu. Rev. Plant Biol. 2008. 59:651–81 The Annual Review of Plant Biology is online at plant.annualreviews.org This article’s doi: 10.1146/annurev.arplant.59.032607.092911 Copyright c  2008 by Annual Reviews. All rights reserved 1543-5008/08/0602-0651$20.00 Key Words salt tolerance, salinity stress, sodium toxicity, chloride, stress tolerance Abstract The physiological and molecular mechanisms of tolerance to os- motic and ionic components of salinity stress are reviewed at the cel- lular, organ, and whole-plant level. Plant growth responds to salinity in two phases: a rapid, osmotic phase that inhibits growth of young leaves, and a slower, ionic phase that accelerates senescence of ma- ture leaves. Plant adaptations to salinity are of three distinct types: osmotic stress tolerance, Na + or Cl − exclusion, and the tolerance of tissue to accumulated Na + or Cl − . Our understanding of the role of the HKT gene family in Na + exclusion from leaves is increasing, as is the understanding of the molecular bases for many other transport processes at the cellular level. However, we have a limited molecular understanding of the overall control of Na + accumulation and of osmotic stress tolerance at the whole-plant level. Molecular genet- ics and functional genomics provide a new opportunity to synthe- size molecular and physiological knowledge to improve the salinity tolerance of plants relevant to food production and environmental sustainability. 651 Annu. Rev. Plant Biol. 2008.59:651-681. Downloaded from arjournals.annualreviews.org by CSIRO on 06/21/08. For personal use only.