Differential Response of Southern US Rice (Oryza sativa L.) Cultivars to UltravioletB Radiation
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Elevated ultraviolet-B (UV-B; between 290 and 320 nm) radiation, because of depletion of the stratospheric ozone layer, is one of the major environmental factors influencing plant metabolic processes and yield. The southern US rice cultivars contribute greatly towards US rice production, but the effects of elevated UV-B radiation on these cultivars are not well known. The objective of this study was to determine the effects of elevated UV-B radiation on leaf photosynthetic rate (Pn), membrane stability, pollen viability, phenolic concentration and yield of eight commercially popular southern US rice cultivars (five inbred cultivars and three hybrids). Plants were grown in a temperature-controlled greenhouse in Beaumont, TX, USA, and were exposed to UV-B radiation of 0, 8 or 16 kJ m-2 day-1 for 90 days. For most of the cultivars, plants grown under 8 or 16 kJ UV-B radiation showed significant decreases in Pn, membrane stability, pollen viability, and yield compared with the plants grown under an UV-B-free environment, whereas there was a significant increase in leaf phenolic concentration under 16 kJ UV-B radiation. The hybrid 'Clearfield XL729' performed best among the selected southern US rice cultivars under 16 kJ UV-B radiation. 2010 Blackwell Verlag GmbH.