Ultraviolet-B induced changes in morphological, physiological and biochemical parameters of two cultivars of pea (Pisum sativum L.).

Increase in perception of solar ultraviolet-B (UV-B) radiation on Earth's surface due to anthropogenic activities has potential in causing detrimental effects on plants. The present study was performed to evaluate the effect of elevated UV-B on Pisum sativum L., a leguminous plant with emphasis on nitrogen metabolism, flavonoids and hormonal changes. Elevated UV-B (ambient+7.2 kJ m(-2) day(-1)) negatively affected the growth, biomass, yield and its quality by generating oxidative stress directly or due to elevation of salicylic acid in two cultivars with higher magnitude being observed in HUP-2 as compared to HUDP-15. The increased accumulation of flavonoids (quercetin and kaempferol) under elevated UV-B neither provided sufficient protection to the photosynthetic machinery nor helped in elevation of biological nitrogen fixation. Nitrogen fixation and its assimilation were negatively affected under elevated UV-B as observed by the decline in nitrogenase, nitrate reductase, nitrite reductase activities and leghaemoglobin contents. Higher accumulation of salicylic acid in HUP-2 might be associated with its higher degree of sensitivity against UV-B, while higher induction of jasmonic acid and antioxidative enzymes (superoxide dismutase, catalase and ascorbate peroxidase activities) provided resistance to HUDP-15 against applied stress vis-a-vis exhibited less reduction in biomass, yield and quality of produce.