Combined effect of ultraviolet-B radiation and cadmium contamination on nutrient uptake and photosynthetic pigments in Brassica campestris L. seedlings

Abstract

Environmental and industrial pollution along with increase in ground level UV-B radiation, because of stratospheric ozone depletion, present multiple stresses, which may affect crop photosynthesis and productivity. The present study was undertaken to see interactive effects of heavy metal contamination (Cd(2+)) and UV-B exposure on essential nutrient (Ca(2+), Mg(2+), K(+)) uptake, biomass, and chlorophyll content in mustard (Brassica campestris L.) seedlings. Plants grown in 0.5, 1.0, 2.5, and 5.0 mg L(-1) Cd(2+) supplemented medium were exposed to UV-B for 30 min (0.4 mW cm(-2)) per day. The interactive effect of two stresses measured after 5 and 10 days showed an overall decline in biomass. Under dual stress (5 mg Cd(2+) L(-1)) significant (P < 0.001) decrease in chlorophyll a (43%), chlorophyll b (23%), and carotenoid (53%) was observed. Ca(2+) uptake was reduced by 51% in roots under high doses of Cd(2+) (5 mg L(-1)) and simultaneous exposure to 0.4 mW cm(-2) UV-B for 10 days. Mg(2+) content was reduced by 48% and K(+) by 62% under similar exposure conditions. Decline in nutrient uptake in Brassica campestris L. seedlings was observed both in root and shoot leaf in the initial growth period under controlled lab conditions. Cadmium ion (Cd(2+)) uptake was significantly enhanced by 33% (P < 0.001) in the presence of UV-B. The findings are significant as multiple stress conditions prevalent in the environment play an important role during the early growth period, a period critical for crop yield.