Allelopathy Journal

We examined the effects of main autotoxic substances (phthalic acid and phloroglucionl dihydrate, separated in our previous study), on root oxidative damage of tomato seedlings. Changes in superoxide dismutase (SOD, EC 1.15.1.1), peroxidase (POD, EC 1.11.1.7), catalase (CAT, EC 1.11.1.6) and malondialdehyde (MDA) and their activities in roots were measured. Potted tomato seedlings were cultured in perlite and treated with phthalic acid (PA) and phloroglucinol dihydrate (PD) as exogenous autotoxins at 1 mM, 5 mM and 10 mM concentrations. The application of both PD and PA, and especially PD increased the MDA contents. The activities of SOD, CAT and POD depended on autotoxins (PA or PD), their time of action and concentration. The enzyme activities increased with application of PA on 5^th day and decreased on 10^th day except at 10 mM PA. On 20^th day, the activities of all enzymes decreased except SOD at 1 mM. Similar trend of enzyme changes was presented in the treatments of PD, except POD activity that kept growing on the 10^th day. Results indicated the adverse effects of exogenous PA and PD on enzymes of antioxidant defence system, resulting in lipid peroxidation in roots of tomato seedlings.