Thursday, November 8, 2007 - 8:45 AM
335-4
Growth and Yield Responses of Southern US Rice (Oryza sativa L.) Cultivars to Supplemental UV-B Radiation.
Depletion of global stratospheric ozone could intensify ultraviolet-B (UV-B)radiation, which can alter rice crop productivity. The objective of these studies was to determine the effects of supplementary UV-B radiation on rice growth, development and physiology with special emphasis on screening for UV-B-tolerant rice cultivars. Eight popular southern U.S. rice cultivars were selected for the UV-B screening process. Plants received no natural UV-B radiation due to the UV-absorption characteristics of the greenhouse glass, hence UV-B was artificially supplied by supplemental UV-B lighting. Plants were grown in soil collected from research plots, and exposed to UV-B radiation of 0, 8 (ambient) or 16 (high) kJ m-2 d-1 for 90 days. Significant differences were observed among rice cultivars in sensitivity to increased UV-B radiation (16 kJ). For most of the cultivars, plants grown under a high UV-B treatment showed significant decreases in plant yield, photosynthesis, primary branches on the main-stem panicle, total number of grains and filled grain weight of the main-stem, compared to plants grown under UV-B-free environment. However, the magnitude of decrease in the above mentioned parameters varied among the cultivars. In our studies, the hybrids were less sensitive to high UV-B radiation (16 kJ) compared to conventional cultivars.
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