Physiological role of anthocyanin accumulation in common hazel juvenile leaves

Common hazel (Corylus avellana L., Fusca rubra Dipp.) juvenile leaves from the periphery of the canopy and thus subjected to high fluxes of solar radiation are characterized by red coloration due to anthocyanin accumulation disappearing in mature leaves. To elucidate the physiological role of anthocyanin accumulation, the interrelations between anthocyanin content, a degree of attenuation by the pigments of the light reaching the photosynthetic apparatus (PSA), and PSA tolerance to photoinhibition in C. avellana juvenile leaves were studied. Absorption spectra were calculated taking into account the light losses due to reflection by the leaf. The analysis of the spectra showed that, in red common hazel leaves accumulating high amounts of anthocyanins in the vacuoles of the upper and lower epidermal cells, up to 95% of visible radiation entering the leaf blade was absorbed by these pigments. The rate of the linear electron transport (ETR) in the chloroplast electron transport chain (ETC) was closely correlated with the anthocyanin content (r ² = 0.87). In red leaves, the saturation of ETR dependence on irradiance was observed at the higher values of PAR than in green leaves. In red juvenile leaves, this value was close to that in mature green leaves tolerant to high light. There were no differences between red and green leaves in the level of non-photochemical quenching, the content of violaxanthin cycle pigments, a degree of their de-epoxidation under natural illumination and at irradiation with high PAR fluxes. Basing on the data obtained, one may conclude that anthocyanins in C. avellana juvenile leaves serve PSA photoprotection, preventing injury of immature PSA with excessive fluxes of PAR.