Integrated studies of the response of the photosynthetic apparatus of the Siberian spruce (Picea obovata Ledeb.) to the effects of UV-B radiation
2010
Vladimir V. Zuev | Nina E. Zueva | Albina P. Zotikova | Olga G. Bender | Vladimir L. Pravdin
The nature of the effect of ultraviolet radiation on the physiological processes of plants depends on the wavelength, intensity and the duration of the exposure. The article presents the results of the integrated study of the effect of ultraviolet radiation on the photosynthetic apparatus of the Siberian spruce (Picea obovata Ledeb.) at a wavelength of 308 nm and the irradiation, which is close to the level of radiation at a given wavelength in the ozone hole within 30 days. The periods of 7-8 days are distinguished. At the boundaries of these periods the response of the photosynthetic apparatus to irradiation varies significantly, depending on the age of the needles. So during the first week of exposure, i.e. within the natural synoptic time-scale, there are no significant changes in the functional state of the photosynthetic apparatus. The second week is characterized by a pronounced decline in photosynthetic pigment content, the quantum yield of primary charge separation of PS II and the intensity of the observed photosynthesis. There is also a respiration increase and the growth of pine needles of the current year is slowing down. In fact, within 15 days, which correspond to an average lifetime of a blocking anticyclone at the lowest levels of total ozone, the action of photo adaptation mechanisms is not observed. Furthermore, the effect of UV-B radiation stimulates the functioning of adaptive mechanisms, resulting in the restoration of the pigment fund. However, the adaptation mechanisms can no longer cope with the effects of abnormal duration influences (more than 3 weeks) of the short UV-B radiation and this leads to serious structural failures and malfunction of the photosynthetic apparatus.
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