Independent Effects of Phytochrome and Nitrate on Nitrate Reductase and Nitrite Reductase Activities in Maize

Involvement of phytochrome in the regulation of nitrate reductase (NR) and nitrite reductase (NIR) activities in excised, etiolated leaves of Zea mays (L.) variety ‘Ganga‐5’ is demonstrated using low energy and high irradiance responses of phytochrome action. Photoreversibility by far‐red light of red light stimulated increases in NR and NIR activities was lost by 2 h. Red light given to the leaves, when induction by NO‐3, was saturated, further increased both enzyme activities. Even if red light was given 4–8 h before NO‐3, it still increased both NR and NIR activities.