Deciduous and evergreen tree responses to enhanced UV-B treatment during three years

Abstract

This paper reports a study of the strategies in Norway spruce (Picea abies (L.) Karst.) and European beech (Fagus sylvatica L.) for coping with enhanced UV-B radiation. Trees, as plants in general, possess diverse systems which respond to UV-B radiation. Changes in physiology, biochemistry and morphology have been observed in trees under enhanced UV-B radiation. The efficiency of trees’ UV-B protective systems depends on plant characteristics and state of development as well as can be correlated with the UV-B dose and the environmental conditions. The two tree species were exposed outdoors to enhanced UV-B simulating 17% ozone depletion for three years during which time, selected parameters were monitored. Selected physiological parameters were monitored three times a year on beech leaves and three needle age classes of spruce. Spruce and beech exhibited great variability in the amounts of chlorophyll, methanol-soluble UV-B and UV-A absorbing compounds, and optimum quantum yield of photosystem II. The effects of UV-B radiation also varied with needle and leaf development stage and interaction with environmental conditions. Enhanced UV-B radiation triggered responses in both trees and a reduced negative effect of UV-B radiation on spruce photochemical efficiency was observed during prolonged drought. The results show high UV-B tolerance of both tree species and indicate the complexity of plant response to UV-B, involving multilevel interactions with environmental factors and thus emphasizes the necessity of long-term investigations on trees in a natural ecosystem.