The effects of solar ultraviolet‐B radiation on the growth and yield of barley are accompanied by increased DNA damage and antioxidant responses

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Abstract
There is limited information on the impacts of present‐day solar ultraviolet‐B radiation (UV‐B) on biomass and grain yield of field crops and on the mechanisms that confer tolerance to UV‐B radiation under field conditions. We investigated the effects of solar UV‐B on aspects of the biochemistry, growth and yield of barley crops using replicated field plots and two barley strains, a catalase (CAT)‐deficient mutant (RPr 79/4) and its wild‐type mother line (Maris Mink). Solar UV‐B reduced biomass accumulation and grain yield in both strains. The effects on crop biomass accumulation tended to be more severe in RPr 79/4 (≈ 32% reduction) than in the mother line (≈ 20% reduction). Solar UV‐B caused measurable DNA damage in leaf tissue, in spite of inducing a significant increase in UV‐absorbing sunscreens in the two lines. Maris Mink responded to solar UV‐B with increased CAT and ascorbate peroxidase (APx) activity. No effects of UV‐B on total superoxide dismutase (SOD) activity were detected. Compared with the wild type, RPr 79/4 had lower CAT activity, as expected, but higher APx activity. Neither of these activities increased in response to UV‐B in RPr 79/4. These results suggest that growth inhibition by solar UV‐B involves DNA damage and oxidative stress, and that constitutive and UV‐B‐induced antioxidant capacity may play an important role in UV‐B tolerance.