Xanthophyll composition and content in the leaves of broad-leaved forest plants including shade-requiring and shade-tolerant herbaceous plants (Polygonatum multiflorum, Convallaria majalis, Asarum europaeum, Aegopodium podagraria) and plants from the shrub layer (Padus avium, Corylus avellana, Euonymus europaeus) were studied. Plants were gathered in midsummer from areas differing 2–3 times in illumination intensity. It was determined that violaxanthin content in the leaves of P. avium and C. avellana diminished with the increase in insolation, that can be caused by violaxanthin cycle functioning. On the contrary, violaxanthin to zeaxanthin transformation in herbaceous plants was obviously suppressed, since violaxanthin content was higher under greater light intensity. Lutein content in the leaves of plants from the shrub layer and C. majalis did not depend on growth conditions. Higher by 10–15% lutein content in the leaves of P. multiflorum and A. europaeum from more shady areas may be the outcome of the necessity to maintain the structural stability of photosystem II light-harvesting complex. The progressive loss of lutein by the leaves of plants from the shrub layer and especially of A. europaeum may be caused by the functioning of the auxiliary xanthophyll cycle, namely the lutein cycle. Together with the violaxanthin cycle, it stimulates energy dissipation inside light-harvesting antenna complexes thus assisting in protecting the photosynthetic apparatus from photoinhibition. The content of neoxanthin, that performs mainly light-harvesting function, was increased in the plants from the shrub layer under restricted illumination. The content of all xanthophyll pigments mainly decreased in time. The dynamic changes in xanthophyll content display the role of these pigments in modulation of the activity of the photosynthetic apparatus. Higher content of certain xanthophyll pigments in plants from more shady areas of broad-leaved forest may be necessary for effective absorption of the restricted amount of photons.
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