The study presents the results of investigation on reaction of beech (Fagus sylvatica L.) leaves observed next year after planting seedlings in different positions in a young spruce stand located in upper mountain conditions. The methods of chemical analyses and assessments of chlorophyll fluorescence were applied with the aim to evaluate a course of leaf adaptation. In the young spruce stand located in the Karkonoše Mts, bare root beech seedlings after cultivation in full light were planted into three main positions to spruce trees (under the crown, within crown perimeter and in stand gaps). Next year after planting, the total biomass, leaf nutrient content and chlorophyll fluorescence parameters were evaluated. The beech trees planted under spruce (Picea sp.) crowns had significantly lower specific leaf mass and the mean leaf area was decreasing from shade to sun. Differences in nutrient contents were not significant between the treatments. We found significantly higher values of minimal (F0) and the maximum fluorescence (Fm) as well as of the maximum quantum yield of PSII photochemistry (Fv/Fm) in the leaves of beeches growing under the spruce crown. Significant differences among treatments were found also in the courses of the values of maximum fluorescence yield Y(II) and nonphotochemical quenching (NPQ). Our study indicated that bud forming processes are only partially responsible for physiological properties of beech leaves evaluated next year after planting. Photosynthetic performance is also influenced by actual growing conditions. A great part of acclimation occurs already in the first year after planting (change of the light conditions). We speculate that this phase of gradual acclimation of the assimilation apparatus can be one of the reasons of physiological weakening of the plant after planting to different light environment.
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