Hot pepper response to interactive effects of salinity and boron

An excess of salinity and boron (B) can limit production of hot pepper (Capsicum annuum L.), but little is known about the physiological responses, including antioxidant activities, in response to these excesses. We investigated the physiological responses and defense mechanisms of hot pepper grown under salinity (NaCl) stress at 3 and 6 dS/mand B stress at 15 and 30 mg/kg. Dry weight and the total chlorophyll content decreased with increasing salinity and B levels. The toxic effect of B was greater under saline conditions. Higher levels of salinity and B resulted in increased B concentrations in leaves. The stomatal resistance values increased as the combined levels of salinity and B increased. Furthermore, increasing salinity, B or both increased activities of H2O2, SOD, POX, APX and GR, which increased oxidative stress, compared to the control plants. Increases in combined salinity and B levels disrupted plant nutrient balance and water use, and induced production of secondary toxic substances leading to an increased plant tissue concentration of H2O2, and suppression of growth in hot pepper.