RESPONSE OF TOMATO CULTIVARS TO SALINITY

The responses of five tomato cultivars (L. esculentum Mill) of differe nt degrees of salt tolerance were examined over a range of 0 to 140 mM NaCl applied for 3 and 10 weeks. Judged by both Na and Cl accumulatio ns and maintenance of K, Ca and Mg contents with increasing salinity, the most tolerant cultivars (Pera and GC-72) showed different response s. The greater salt tolerance of cv Pera was associated with a higher Cl and Na accumulation and a lower K content in the shoot than those f ound in the other cultivars, typical of a halophytic response to salin ity. However, the greater salt tolerance of cv GC-72 was associated wi th a retention of Na and Cl in the root, restriction of their transloc ation to the shoot and maintenance of potassium selectivity under sali ne conditions. The salt tolerance mechanisms that operated in the rema ining cultivars were similar to that of cv GC-72, as at first they exc luded Na and Cl from the shoots, accumulating them in the roots; with longer treatment, the ability to regulate Na and Cl concentrations in the plant was lost only in the most salt sensitive cultivar (Volgograd skij), resulting in a massive influx of both ions into the shoot. The salt sensitivity of some tomato cultivars to salinity could be due to both the toxic effect of Na and Cl ions and nutritional imbalance indu ced by salinity, as plant growth was inversely correlated with Na and Cl contents and directly correlated with K and Ca contents. This study displays that there is not a single salt tolerance mechanism, since d ifferent physiological responses among tomato cultivars have