Response of Three Conifer Species to Enhanced UV-B Radiation; Consequences for Photosynthesis
E. Brzezinska1, M. Kozlowska1, J. Stachowiak2
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1Department of Plant Physiology, 2Department of Chemistry, August Cieszkowski Agricultural University, Wołyńska 35, 60-637 Poznań, Poland
Pol. J. Environ. Stud. 2006;15(4):531-536
Investigations were carried out to find whether enhanced ultraviolet radiation influences the Taxus, Thuja and Juniperus genera used in garden architecture. Seedlings a few years old were subjected to UV-B at a 16 kJ m-2 day-1 dose for several weeks. Carbohydrate contents (monosaccharides and sucrose), levels of chlorophylls and chlorophyll a fluorescence were analyzed, and the variable/maximal fluorescence (Fv/Fm) and the Rfd– vitality index were calculated. In Taxus and Juniperus no negative effects were found in carbohydrate accumulation and even increased chlorophyll a and b levels were noted. After 6-9 weeks of irradiation the amount of these pigments in Juniperus needles was as many as twofold higher. Under the in fluence of UV-B a 50% reduction of monosaccharide accumulation was found only in Thuja, after 3 weeks irradiation, and an approx. 30% reduction in chlorophylls after 6-9 weeks of irradiation. no changes in the Fv/Fm parameter were found in either species, but the vitality index (Rfd) under the first weeks of radiation stress showed even an increase in Thuja leaves. These results indicate that shoot blight of conifers is not caused by enhanced UV-B radiation.
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