Effect of UV-B radiation on antioxidative enzyme activity in cucumber cotyledons.

Ultraviolet-B (UV-B) radiation negatively affects plant cells, causing reactive oxygen species (ROS) to be generated. To study the effects of increased UV-B exposure on antioxidant processes, we exposed germination-stage cucumber seedlings to increased ultraviolet radiation and analyzed hydrogen peroxide content and the activity of superoxide dismutase (SOD), catalase (CAT), guaiacol peroxidase (GPX) and syringaldazine peroxidase (SPX). Enzymatic antioxidant system activity generally increased after UV-B supplementation. Activation of CAT, GPX and SPX in cucumber cotyledons correlated positively with increases in SOD activity and hydrogen peroxide content. The results indicate that ROS accumulated despite higher engagement of the enzymatic antioxidant system, and that elevated UV-B radiation triggered oxidative stress in the cucumber cotyledons.