Circadian Rhythm of Nitrate Reductase Activity in Jatropha curcas Under Different Photoregimens

Our knowledge on the circadian phenomenon in Jatropha curcas is limited. Therefore, we studied the activity of nitrate reductase (NR) in leaves of J. curcas under light and dark cycles (LD 12:12), continuous light (LL) and constant darkness (DD). We observed a statistically significant circadian rhythm in NR activity in LD. Unlike in DD, the circadian oscillation in NR activity persisted in continuous light, irrespective of different light intensities (LL 2 lx and 15 lx). The peak activity of NR appeared in the morning in LL 15 lx and forenoon in LD, while it reached a peak at night in LL 2 lx. This shows that rhythm in NR activity in J. curcas could be endogenous and that the light intensity might modulate acrophase of NR activity. Jatropha curcas could be considered as an ideal higher plant model for teaching NR activity rhythm to undergraduate and postgraduate students of biology streams.