Nitrate Reductase Activity in Corn Seedlings as Affected by Light and Nitrate Content of Nutrient Media

Young corn plants placed in complete darkness for 48 hours lost 90% of their nitrate reductase activity. The activity was quickly restored when the plants were returned to the light. In other experiments, corn plants were grown under artificial shade in the greenhouse. The nitrate reductase activity in these plants decreased roughly in proportion to the amount of shading. It was shown that both light and nitrate are necessary for the formation of nitrate reductase in quantities required by the plant for normal growth. Corn seedlings germinated in the dark in Hoagland solution showed a fourfold increase in nitrate reductase within 8 hours after they were transferred into the light. Plants that were germinated in the dark without nitrate, and given nitrate at the same time they were transferred to the light, showed a slower rate of development of nitrate reductase activity. Green house experiments in which the nitrate content of nutrient media was varied showed that the level of nitrate reductase activity was dependent in part upon the substrate concentration. There was a positive correlation between the nitrate reductase activity and the growth and protein content of both strains. 18 references, 5 figures, 4 tables.