DEVELOPMENT OF ANTIOXIDATIVE DEFENSE SYSTEM OF WHEAT SEEDLINGS IN RESPONSE TO HIGH LIGHT

Changes in the activities of enzymes involved in the detoxification of reactive oxygen species in wheat seedlings (Triticum aestivum L.) in response to variations in the light environment were studied. Activiti es of ascorbate peroxidase, superoxide dismutase, monodehydroascorbate reductase, dehydroascorbate reductase, glutathione reductase and cata lase were much lower in seedlings grown under low-light conditions tha n in those grown under high-light conditions. Activities of all these enzymes significantly increased within 24 h of transfer of the low-lig ht-grown seedlings to the high-light regime. The results suggest that the increase in enzyme activities was an adaptive response of the plan ts to higher amounts of active oxygen species generated at higher ligh t intensities. An accumulation of glutathione was also observed which could also be a part of the defense strategy to meet the increased gen eration of active oxygen species upon transfer of low-light-grown plan ts to high-light conditions.