GROWTH AND OSMOTIC ADJUSTMENT OF 2 TOMATO CULTIVARS DURING AND AFTER SALINE STRESS

The effect of a short period of saline stress was studied in two phenotypically different cultivars, one of normal fruit-size (L. esculentum cv. New Yorker) and one of cherry fruit-size (L. esculenturn var, cerasiforme cv. PE-62). In both cultivars the relative growth rate (RGR) and the leaf area ratio (LAR) decreased following salinisation. The leaf turgor potential (psi(p)) and the osmotic potential at full turgor (psi(os),,) decreased to the same extent in both cultivars. However, the contributions of organic and inorganic solutes to the osmotic adjustment was different between cultivars. New Yorker achieved the osmotic adjustment by means of the Cl- and Na+ uptake from the substrate, and by synthesis of organic solutes. In the cherry cultivar organic solutes did not contribute to the osmotic adjustment, instead, their contribution decreased after salinisation. After the salt stress was removed, the water stress disappeared, the content of organic solutes decreased in plants of both cultivars and, therefore, their growth was not retarded by the diversion of resources for the synthesis of organic solutes. However, the toxic effects of the Cl- and Na+ did not disappear after removal of the salt stress, and the net assimilation rate (NAR) and the rate of growth (RGR) did not recover.