Potential biochemical indicators of salinity tolerance in plants

Despite a wealth of published research on salinity tolerance of plants, neither the metabolic sites at which salt stress damages plants nor the adaptive mechanisms utilized by plants to survive under saline conditions are well understood. As a result, there are no well-defined indicators for salinity tolerance available to assist plant breeders in the improvement of salinity tolerance of important agricultural crops. Although plant breeders have successfully improved salinity tolerance of some crops in recent decades, using plant vigor or seed yield as the main selection criteria, selection may be more convenient and practicable if the crop possesses distinctive indicators of salt tolerance at the whole plant, tissue or cellular level. Thus, there is a need to determine the underlying biochemical mechanisms of salinity tolerance so as to provide plant breeders with appropriate indicators. In this review, the possibility of using these biochemical characteristics as selection criteria for salt tolerance is discussed. It is concluded that although there are a number of promising selection criteria, the complex physiology of salt tolerance and the variation between species make it difficult to identify single criteria. Progress is more likely if biochemical indicators for individual species rather than generic indicators can be determined. (C) 2003 Elsevier Ireland Ltd. All rights reserved.