Effect of UV-B (290–320 nm) irradiation on growth and metabolism of cucumber cotyledons |
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Authors: | Yuichi Takeuchi Megumi Akizuki Hideyuki Shimizu Noriaki Kondo Kiyoshi Sugahara |
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Affiliation: | Division of Environmental Studies, Tsukuba, Ibaraki 305, Japan;Faculty of Science, Toho Univ., Funabashi, Chiba 274, Japan;Dept of Bioscience and Technology, School of Engineering, Hokkaido Tokai Univ., Minamisawa, Sapporo 005, Japan. |
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Abstract: | Cucumber ( Cucumis sativus L. cv. Natsusairaku 3) seedlings were grown in a growth cabinet under UV-B (290–320 nm) irradiation (equivalent to the UV-B radiation normally incident at Tokyo, 36°N latitude, during clear sky conditions in mid-april on a weighted daily fluence basis) and a UV-B-free control condition. UV-B irradiation inhibited the growth of the cotyledons, i.e. the increase in area, and increase in fresh and dry weights of the cotyledons. The greatest inhibition rate was observed in the increase in area, causing a significant increase in specific leaf weight (the ratio of weight to area). UV-B irradiation had no significant effect on DNA and RNA contents in the cotyledons, but decreased protein content slightly. In contrast, the irradiation reduced the amounts of organic acids and soluble sugars, indicating that primary carbon metabolism was very sensitive to UV-B radiation. UV-B irradiation lowered the photosynthetic activity in the cotyledons without any effect on chlorophyll content and respiratory activity. These results indicate that UV-B radiation at the ambient level may act as a physiological stress in some UV-sensitive plants. |
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Keywords: | Cucumber cotyledon Cucumis sativus growth inhibition ozone depletion photosynthesis ultraviolet-B radiation |
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