OXIDATIVE STRESS AND ANTIOXIDATIVE MECHANISMS IN TOMATO (SOLANUM LYCOPERSICUM L.) PLANTS SPRAYED WITH DIFFERENT PESTICIDES

A glasshouse experiment was conducted to appraise the influence of exogenously applied pesticides such as abamectin, thiamethoxam, pyriproxyfen and acetamiprid on oxidative defence system and some key physiological attributes in tomato (Solanum lycopersicum L.). Each of these pesticides was applied in three doses (recommended dose, twice and three times higher than the recommended dose). Higher doses of pesticides sprayed to the plants resulted in marked increase in leaf free proline content and electrolyte leakage, but in a decrease in shoot dry matter, chl a, chl b and chl a+b in tomato plants as compared to those plants not sprayed with pesticides. These reductions were greater in tomato plants sprayed with highest doses of thiamethoxam (144 mg L-1), whereas the reverse was true for proline content and electrolyte leakage. The foliar application of pesticides at the highest levels caused enhanced accumulation of malondialdehyde (MDA) in most cases, and these being greater in treatment of foliar application of thiamethoxam at the highest level. The highest doses of pesticides promoted the activities of catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD) in most cases. The results clearly indicate that application of pesticides at higher doses than recommended doses provoked both oxidative and antioxidative systems in tomato plants.