The response of Siberian spruce (Picea obovata Ledeb.) photosynthetic apparatus to enhanced UV-B radiation effect
V.V. Zuev, N.E. Zueva, E.M. Korotkova, O.G. Bender
Institute for Monitoring of Climatic and Ecological Systems of the RAS, 634055, Tomsk, Akademichesky Ave., 10/3
Keywords: фотосинтетический аппарат, УФ-В-радиация, наблюдаемый фотосинтез, транспирация, водный баланс, photosynthetic apparatus, UV-B radiation, observed photosynthesis, transpiration, water balance
Abstract
The action of enhanced UV radiation at the 308 nm wavelength on the photosynthetic apparatus of Siberian spruce seedlings (Picea obovata Ledeb.) from June to August has been studied in two-year experiment. The negative effect on the photosynthetic apparatus of spruce needles is ascertained, with a pronounced cumulative effect. The suppression of the photosynthesis rate and transpiration intensity in the radiation-exposed two-year spruce needles and current-year spruce needles, primordia formed in July-September of the previous vegetation period, is shown to be deeper during the second vegetation period as compared to the first one. We revealed that the water balance of spruce needles corresponded to seasonal norms in the both groups during the experiment. The decrease of the transpiration intensity in the spruce seedlings exposed to radiation as compared to the control group is conditioned by a need in maintaining the water homeostasis in the needles. The experimental group of spruce seedlings showed a weaker correlation between the photosynthesis rate and transpiration intensity than the control group, which is clearly pronounced in the two-year needles exposed to the radiation.
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