Effect of phytochrome and kinetin on nitrite reductase activity in Zea mays

Abstract

Red light and kinetin (10 μm) increased nitrite reductase (NIR) activity by 85 and 47% respectively in excised leaves of etiolated Zea mays. The stimulatory effect of kinetin decayed slower than that of red light. Indoleacetic acid (10 μm) had no effect on NIR activity. In the presence of abscisic acid (10 μm), the kinetin stimulated increase in NIR activity was totally nullified, however, the red light irradiated plants retained 20-25% increase in NIR activity over the dark control. If ABA was given 2 h after kinetin treatment or red light irradiation, it totally blocked kinetin stimulation as noticed earlier, but red light stimulation was inhibited by only 11%. Kinetin-treated and the red light irradiated leaves showed 20-25% increase in nitrate accumulation, which was totally nullified by ABA. The experiments presented suggest an independent mode of signal transduction by kinetin and phytochrome in stimulating NIR activity.