OXIDATIVE STRESS INJURY IN TOMATO PLANTS INDUCED BY SUPPLEMENTAL UV-BRADIATION

Tomato (Lycopersicon esculentum Mill. cv. PKM 1) plants growing under field conditions were exposed for 15 d to solar radiation with W-B com ponent (280 - 320 Ka) enhanced to 6.3 kJ m(-2) d(-1). This simulated a 15 % stratospheric ozone depletion over Madurai (9 degrees 50' N lati tude). Lipid peroxidation in the leaves of UV-B treated plants was 32 % higher compared to the control. Superoxide dismutase (SOD) and catal ase activities registered parallel promotion by 126 and 50 %, respecti vely, in the UV-B treated plants. Further, the contents of total pheno ls and anthocyanins in the leaves have also been enhanced by 40 and 15 6 %, respectively. On the contrary, polyphenol oxidase activity demons trated a 58 % inhibition in the leaves of UV-B treated plants. While a nthocyanins and phenols are proposed to act as antioxidants, the reduc tion in polyphenol oxidase activity may maintain the turnover of pheno ls in the UV-B treated plants.