ENHANCEMENT OF SALINITY TOLERANCE IN TOMATO - IMPLICATIONS OF POTASSIUM AND CALCIUM IN FLOWERING AND YIELD

Five tomato (Lycopersicon esculentum Mill ) cultivars were grown in sand nutrient culture experiment in a greenhouse to investigate the effects of salinity on growth and yield. Nutrient solutions were made saline with 50 mM NaCl (EC = 5.5 mS/cm or supplemented with 2 mM KNO3 (EC = 6.8), 20 mM Ca(NO3)2 (EC = 7.5), and combination of potassium (K) and calcium (Ca) (EC = 8.0). Seedlings were irrigated with saline treatments commencing two weeks after transplanting. Determination of sodium (Na) and K in tomato leaves and fruits were by flame photometry. Accumulation of Na in tomato fruits was higher than in leaves under control or saline conditions for all tomato cultivars. The amount of K in the tomato leaves was higher in control than in saline-grown plants. Addition of K and Ca to the nutrient solution resulted in a 3 to 7 fold increase in K accumulation in all cultivars tested. Stem and leaf growth were significantly reduced with salinity but growth was enhanced following irrigation when K was added to the nutrient solution. Flowering and fruit set were adversely affected by NaCl stress. Reduction of flower number was 44% relative to the control plants. Fresh fruit yield decreased by 78% when plants received 50 mM NaCl. Growth and development of tomatoes under saline conditions was enhanced in this study following the application of K to the saline nutrient solution. Amelioration in growth was also achieved when Ca was used but to a lesser extent. Our results suggest that ion accumulation and regulation of K and Ca contribute to salt tolerance and growth enhancement.