Variations in Endogenous Growth Hormones in Rice Under Two Light Intensities

Analysis of endogenous growth regulator concentrations in different parts (viz., leaf, root and panicle) of shade tolerant ( Ponni ) and susceptible ( Bhavani ) rice cultivars a week after flowering indicated that the former was endowed with higher levels of auxin, gibberellin, cytokinin, and abscisic acid contents than the latter. The concentrations of auxin and cytokinin decreased while that of gibberellin and abscisic acid increased under low light conditions in both the varieties. Nevertheless, cytokinins and auxins were only marginally affected under subdued light in Ponni than in Bhavani indicating that better performance of rice cultivars under low light situations of monsoon season might be associated particularly with higher concentrations of auxin and abscisic acid.