The Effects of Ultraviolet Irradiation on Photosynthesis by Ruppia Maritima L. (Widgeon Grass)
Net photosynthesis by Widgeon grass, Ruppia maritima L. is significantly reduced following exposure to simulated solar UV-B radiation at a constant dose rate of 2.0 sunburn units hr−1. A 36% inhibition of photosynthesis is observed when plants are exposed to ambient levels of UV-B (approximately 25 sunburn units day−1 on a clear day in the vicinity of the Johnson Space Center). Photosynthetic inhibition increased linearly to about 20–25% with increasing exposure of UV-B to 15 sunburn units (approximately 60% of the surface irradiance). Above 15 sunburn units its inhibition increases more slowly to 40–45% at 50 sunburn units. This study indicates that net photosynthesis by Widgeon grass is very sensitive to UV-B irradiation, that ambient levels of UV-B have the potential to significantly reduce net photosynthesis and, there does not appear to be a threshold level of UV-B exposure below which no significant reduction in photosynthesis is observed.
KeywordsSolar Zenith Angle Leaf Section Chamber Trial Solar Ultraviolet Radiation Growth Chamber Experiment
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