Effects of Continuous Light/Dark and 2,5-Norbornadiene (1,5-Cyclooctadiene) on Glucose-6-phosphate Dehydrogenase Activity in Spinach Leaves

Abstract

Effects of continuous light/dark and the cyclic olefin 2,5- norbornadiene (NBD; 1,5-cyclooctadiene) on the glucose-6- phosphate dehydrogenase activity (G6PD, EC.1.1.1.49) in spinach leaves were investigated. Plants were grown in sand culture under greenhouse (12:12-h light/dark) condition for 30 d. To examine the effect of NBD; 2 μL pure NBD, 5 μL pure NBD and 5 μL NBD/10 mL water were applied to the plants. The results show that G6PD activity was inhibited in the light and was reactivated in the dark both of the opened control and the closed control. In this study, it is shown for the first time that G6PD can have low and high activity form in the continuous light and the dark regimes. The G6PD shows circadian rhythm. In the leaves with NBD, G6PD activity values increased with respect to the control group under both light and dark periods. Since G6PD is affected by the cyclic olefin NBD, an inhibitor of ethylene action, ethylene because plants have not NBD in normal conditions can have a role in regulation process of this enzyme or NBD can be a stress factor for plants.