Antiperoxidative enzymes in Retama and their seasonal variation.

The antiperoxidative enzymatic activities of ascorbate peroxidase, dehydroascorbate reductase, glutathione reductase and catalase and the content of the antioxidants ascorbate and glutathione were followed in the legume Retama (Retama reatem) in the desert. Antiperoxidative enzymatic activities and antioxidants content were related to seasonal variations in irradiance and precipitation. Retama was found to possess a very efficient removal mechanism for hydrogen peroxide as was shown by the high catalase activity and the high affinity of the ascorbate-glutathione pathway enzymes to their substrates. The increase in irradiance during the spring (March to May) was accompanied by increasing antioxidative enzymatic activities and ascorbate content. A marked enhancement in catalase activity also accompanied the increased light intensity during the spring. Changes in the enzymatic activities of the ascorbate-glutathione pathway followed the increased ascorbate content. These results suggest that physiological adaptation of Retama involves efficient H2O2 removal mechanisms which respond to different seasonal and environmental stresses.