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

Five tomato (Lycopersicon esculentum Mill ) cultivars were grown in sa nd nutrient culture experiment in a greenhouse to investigate the effe cts of salinity on growth and yield. Nutrient solutions were made sali ne 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) an d calcium (Ca) (EC = 8.0). Seedlings were irrigated with saline treatm ents commencing two weeks after transplanting. Determination of sodium (Na) and K in tomato leaves and fruits were by flame photometry. Accu mulation of Na in tomato fruits was higher than in leaves under contro l or saline conditions for all tomato cultivars. The amount of K in th e tomato leaves was higher in control than in saline-grown plants. Add ition of K and Ca to the nutrient solution resulted in a 3 to 7 fold i ncrease in K accumulation in all cultivars tested. Stem and leaf growt h were significantly reduced with salinity but growth was enhanced fol lowing irrigation when K was added to the nutrient solution. Flowering and fruit set were adversely affected by NaCl stress. Reduction of fl ower number was 44% relative to the control plants. Fresh fruit yield decreased by 78% when plants received 50 mM NaCl. Growth and developme nt of tomatoes under saline conditions was enhanced in this study foll owing the application of K to the saline nutrient solution. Ameliorati on 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.