Abstract

A systematic experiment was conducted to examine the effects of main autotoxic substances (benzoic acid and cinnamic acid), which was separated in our previous study, on roots oxidative damage of tomato seedlings. Potted tomato seedlings were cultured in perlite and treated with benzoic acid (BA) and cinnamic acid (CA) as exogenous autotoxins. Changes of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and malonaldehyde (MDA) in roots were measured. The results showed that MDA contents were enhanced when treated with both BA and CA, especially in BA with a concentration of 10 mM on the 20^thday. Activities of SOD, CAT and POD varied depending on autotoxins (BA or CA), their time of action and concentration. The SOD activity was increased by BA on the 5^th day but decreases on the 10^th and 20^th day, which was increased by CA on the 5^th and 10^th day but decreases on the 20^th day. The POD activity was enhanced on the 5^th and 10^th day (except the 10 mM CA on the 10^th day), but reduced on the 10^th day. With the application of both BA and CA, the CAT activity presented a peal on the 10^th day and was inhibited on the 20^th day and even under the level of the control. Results indicated the adverse effects of exogenous BA and CA on enzymes of antioxidant defence system resulting in lipid peroxidation in roots of tomato seedlings.

Key words: Exogenous autotoxins, enzymes of antioxidant defence system, lipid peroxidation, tomato seedling.