Synergistic action of ultraviolet-B radiation and cadmium on the growth of wheat seedlings.

The increase in ground level UV-B radiation as a result of stratospheric ozone depletion may have major deleterious effects on crop photosynthesis and productivity. Plants are exposed to UV-B and other xenobiotics simultaneously in today's industrialized world. The present studies were undertaken to see the effect of dual stress of UV-B and Cd2+ exposure on the growth of wheat (Triticum aestivum L.) seedlings. The plants grown in 0.25, 0.5, 1.0, 2.5, and 5.0 ppm Cd2+-supplemented medium were exposed to UV-B for 30 min (2 J, 0.4 mW/cm(2)) per day. After 5 and 10 days of treatment the combined stress of UV-B and Cd2+ resulted in reduction of biomass yield, growth, and chlorophyll content and changes in protein, free amino acid, starch, and total reducing sugar content. These data support the assumption that UV-B may have a regulatory role besides damaging effects and that an increased UV-B environment will likely increase this regulatory influence of UV-B radiation. The results also indicate that the adverse effects of one stress may be modulated in the presence of other stresses.