Supplementary potassium nitrate improves salt tolerance in bell pepper plants

The effect of supplementary potassium nitrate (KNO3) on growth and yield of bell pepper (Capsicum annum cv. 11B 14) plants grown in containers under high root-zone salinity was investigated. Treatments were (1) control, soil only and (2) high salt treatment, as for control plus 3.5 g NaCl kg(-1) soil. Above treatments were combined with or without either 0.5 or 1 g supplementary KNO3 kg(-1) soil. Plants grown at high NaCl had significantly less dry matter, fruit yield, and chlorophyll than those in the control treatment. Supplementing the high salt soil with 0.5 and 1 g KNO3 kg(-1) increased plant dry matter, fruit yield, and chlorophyll concentrations as compared to high salt treatment. Membrane permeability increased significantly with high NaCl application, but less so when supplementary KNO3 was applied. High NaCl resulted in plants with very leaky root systems as measured by high K efflux; rate of leakage was reduced by supplementary KNO3. These data suggest that NaCl status affect root membrane integrity. Sodium (Na) concentration in plant tissues increased in leaves and roots in the elevated NaCl treatment as compared to control treatment. Concentrations of K and N in leaves were significantly lower in the high salt treatment than in the control. For the high salt treatment, supplementing the soil with KNO3 at 1 g kg(-1) resulted in K and N levels similar to those of the control. These results support the view that supplementary KNO3 can over come the effects of high salinity on fruit yield and whole plant biomass in pepper plants.