Diurnal Fluctuations in the Activity of the Enzyme Nitrate Reductase in Lemna paucicostata

Abstract

Diurnal fluctuations were observed in nitrate reducta.se activity in Lemna paucicostatu Hegelm, grown under 16‐h photoperiod. The enzyme activity showed a single peak in the middle of the photo period, i.e. 8 h after the onset of light. The activity decreased during the latter half of the photoperiod and reached a minimum level in the middle of the dark period. The peak in enzyme activity persists in continuous light as well as continuous dark, at least for a couple of days, suggesting the existence of endogenous rhythmicity

EFFECTS OF TEMPERATURE, LEVELS OF NITRATE SUPPLY AND DURATION OF LIGHT AND GROWTH ON NITRATE REDUCTASE ACTIVITY IN AGEOSTIS TENUIS AND AGROSTIS STOLONIFERA

“…It was realized, however, that judgement might have been affected because measurements of activity were made at only one moment during the day. There are many reports of the existence of regular patterns of variation in NRA, both on a daily basis (Bowerman and Goodman, 1971;Steer, 1974a;Devi and Maheshwari, 1979) and on a seasonal basis (Harper and Hageman, 1972;Franco, Pereira and Neyra, 1979;Osborne, 1979).…”