Oxidative stress injury in tomato plants induced by supplemental UV-B radiation

Tomato (Lycopersicon esculentum Mill. cv. PKM 1) plants growing under field conditions were exposed for 15 d to solar radiation with W-B component (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 latitude). Lipid peroxidation in the leaves of UV-B treated plants was 32 % higher compared to the control. Superoxide dismutase (SOD) and catalase activities registered parallel promotion by 126 and 50 %, respectively, in the UV-B treated plants. Further, the contents of total phenols and anthocyanins in the leaves have also been enhanced by 40 and 156 %, respectively. On the contrary, polyphenol oxidase activity demonstrated a 58 % inhibition in the leaves of UV-B treated plants. While anthocyanins and phenols are proposed to act as antioxidants, the reduction in polyphenol oxidase activity may maintain the turnover of phenols in the UV-B treated plants.