Interaction of light quality and benzimidazole on pigment contents and on photochemical activity of chloroplasts isolated from detached senescing wheat (Triticum aestivum) leaves

The possibilities of an interaction between light and the growth regulator benzimidazole in retarding senescence-induced changes in activity of chloroplasts isolated from detached wheat ( Triticum aestivum L. cv. Kalyansona) leaves have been investigated. The effect of benzimidazole on the rate of degradation of chlorophylls in light depended on the quality of light used. Far-red irradiation given to detached leaves in the presence of benzimidazole retarded the pigment loss more significantly than did white or red light of similar intensity. Senescence-induced loss in chloroplast photochemical activity was higher than the loss of chlorophylls. Loss of photosystem I activity was greater than photosystem II activity. Benzimidazole maintained the gramicidin-mediated enhancement in whole chain electron transport uniformly throughout the incubation period irrespective of the light quality. There was no effect of light and benzimidazole in retarding the loss in photochemical activity, although the same preserved the chlorophyll contents as well as characteristics of the chloroplast absorption spectrum.