Effects of presowing gamma irradiation on the photosynthetic pigments, sugar content and carbon gain of Cullen corylifolium (L.) Medik

Abstract

To determine the effects of gamma radiation on the photosynthetic pigments, sugar content and total carbon gain, seeds of Cullen corylifolium (L.) Medik. were irradiated with variable doses (0, 2.5, 5, 10, 15, and 20 kGy) at the rate of 1.65 kGy h-1 from 60Co gamma source. Cullen corylifolium represents an important Chinese medicine with adequate levels of secondary metabolites, thus we hypothesized that gamma irradiation could modulate primary metabolites which could supplement secondary metabolite levels. The seeds were then transferred to field for biochemical analysis at different developmental stages; pre-flowering, flowering and post-flowering. Gamma dosage at 10 kGy resulted in a significant increase in concentration of chlorophyll a (61.17%), chlorophyll b (93.18%) and total chlorophyll (71.66%), suggesting that low doses of radiation could activate photosynthetic pigment system while at 15 and 20 kGy dose resulted in depletion of such parameters. Sugar and total C analysis of plants irradiated at 10 kGy demonstrated significantly maximum (216.01%) sugar content in leaves at all developmental stages and significantly minimum (46.13%) and (57.81%) in plants raised from seeds irradiated at 15 and 20 kGy respectively. Effective stimulatory dose for C. corylifolium '11062' is 10 kGy. In contrast, the carotenoid content of the plants exposed to 15 and 20 kGy was maximum than control. Significance of such stimulation correlated with increasing C mass of the plant concerned is discussed in the light of newer aspects in research.