Salt Resistance

Salt resistance varies among plant genotypes. It can be determined by comparing plant performance under control conditions and salt stress. Priming during germination can increase the salt resistance in later physiological stages. However, it is not possible to estimate the salt resistance of a crop plant during vegetative or generative growth from its performance during germination and vice versa. Germination of halophytes (e.g. sugar beet) is more sensitive to salt stress than that of glycophytes (e.g. maize). Leaf elongation under salt stress is limited by cell-wall extensibility in Phase I. The limitation of leaf elongation in sensitive genotypes can be controlled by various mechanisms. Sink activity under salt stress, both in the vegetative and generative stage, is controlled by the key enzymes acid invertase and plasma membrane H+ ATPase. Both may limit phloem unloading of sucrose and loading of hexoses into sink cells. In Phase II, various mechanisms of Na+ transport contribute to important strategies of Na+ inclusion (in cell vacuoles) and Na+ exclusion (at the root surface and from the shoot). There is strong evidence that energy deficiency does not limit growth or yield formation under salt stress. Therefore, energy-saving traits do not deserve priority in breeding programs.