Effects of supplemental UV-B radiation on growth and leaf photosynthetic reactions of soybean (Glycine max) |
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Authors: | C V Vu L H Allen Jr L A Garrard |
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Institution: | Science and Education Administration, Agricultural Research, U.S. Department of Agriculture, and Agronomy Department, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, Florida 32611, USA. |
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Abstract: | Experiments were conducted under greenhouse conditions to investigate the effects of enhanced UV-B radiation (280 to 320 nm) on height, fresh and dry weights, leaf chlorophyll and carotenoids, CO2 uptake rates, and Hill activity in soybean ( Glycine max L. cv. Bragg). Plants were exposed for 6 h continuously from midmorning to midafternoon each day to UV-B radiation which was provided by Westinghouse FS-40 sun lamps filtered with 0.127-mm cellulose acetate film (UV-B enhanced) or 0.127-mm Mylar S film (UV-B Mylar control). Three different UV-B enhanced radiation levels were tested: 1.09 (treatment T1), 1.36 (treatment T2), and 1.83 (treatment T3) UV-B sun equivalent units (UV-Bsec) where 1 UV-Bsec= 15.98 mW·m?2 of solar UV-B obtained by applying EXP -(α-265)/21]2, a weighting function that simulates the DNA absorption spectrum, to the UV-B lamp systems. These UV-B levels correspond to a calculated decrease in stratospheric ozone content of 6%, 21%, and 36% for treatment T1, T2, and T3, respectively. Daily exposure of soybean plants to UV-B radiation significantly decreased height, fresh and dry weights, leaf chlorophyll and carotenoid contents, and CO2 uptake rates. Leaf pigment extracted in 80% acetone from UV-B-treated soybean plants showed considerable increase in absorption in the wavelength region of 330 to 400 nm with increased UV-B radiation levels. Chloroplast preparations from leaves of T2 and T3 plants showed significant reductions in Hill reaction measurements. |
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Keywords: | Ultraviolet radiation ozone reduction sun lamps leaf pigments |
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