The interactive effects of enhanced UV-B radiation and soil drought on spring wheat

The combined effects of enhanced UV-B radiation and soil drought on the phenological development, photosynthetic pigments, ultraviolet absorbing compounds (e.g. flavonoids), physiological characteristics, biomass and yields of spring wheat (Triticum aestivum L.) under and and semiarid field conditions were investigated in this study. The enhanced UV-B-BE radiation was 4.25 W in 2 day 1, which simulated 20% stratospheric ozone depletion on clear summer solstice (Lanzhou, 1550 m above sea level, China). Soil moisture was maintained at 20% (control groups) and 15% (drought stress groups) by water-irrigation periodically. Phenology was delayed by increased UV-B radiation and the combination of UV-B and drought. In contrast, it was prompted by drought as compared with control in all cultivars. In UV-B- or drought-treated plants, pigments contents (chlorophyll a and b), leaf relative water content and water potential were reduced, However, lipid peroxidation products (NIDA) and membrane permeability (relative electronic conductance) increased, and UV-B absorbing compounds (e.g. flavonoids) were induced by UV-B or water stress. Enhanced UV-B radiation or drought could decrease the net photosynthetic capacity through different paths, and led to the reduction of root, stem and leaves biomass and yield, as well as changed biomass and the harvest index. The plant growth, photosynthetic capacities, pigment contents, biomass and yield were reduced by the combination of two stresses in comparison with single stresses. The results suggested that co-stresses of supplementary `UV-B radiation and drought Synergistically functioned and one of them could alleviate the inhibitory effects of another under the condition of and and semiarid loessial soils. In addition, the earlier-ripped cultivar was better than middle or later-matured cultivars in response to the stress. (c) 2007 SAAB. Published by Elsevier B.V. All rights reserved.