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 20thday. 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 5th day but decreases on the 10th and 20th day, which was increased by CA on the 5th and 10th day but decreases on the 20th day. The POD activity was enhanced on the 5th and 10th day (except the 10 mM CA on the 10th day), but reduced on the 10th day. With the application of both BA and CA, the CAT activity presented a peal on the 10th day and was inhibited on the 20th 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.
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