Effect of Plant Age and Saline Water on Antioxidant and Peroxidase Activity in Sweet Pepper Fruit

Sweet pepper (Capsicum annuum L.) fruits are an excellent source of bioactive products but the content of the same is related with the plant response to stressful conditions. Salinity is among the major constrains restricting to growth and development of plants, and optimizing irrigation strategies could improve fruit quality while saving good quality water. Mature fruits from plants grown at two saline concentrations (20 and 40 mM NaCl), beginning 50, 100 and 150 days after transplanting and a control (0 mM NaCl) were studied. Vitamin C levels fell as the salt concentration in the irrigation increased, while total phenolic compounds and POD activity rose. Additionally, early harvested fruits (young plants) produced fruits with higher concentration of vitamin C than those harvested later, but total phenolic compounds and POD activity showed the opposite behaviour. Marketable yield was also affected by the moment of salinization. Thus, the late the saline stress was imposed, the more attenuated was the effect on the studied parameters. The intensity of fruit response to salinity was significantly modulated by the age of the plant. Therefore, in addition to the level and duration of saline stress imposed, plant age should also be considered when determining the optimum irrigation strategy.