The optical properties of leaves from five species, Norway maple (Acer platanoides L.), cotoneaster (Cotoneaster alaunica Golite), hazel (Corylus avellana L.), Siberian dogwood (Cornus alba L.), and Virginia creeper (Parthenocissus quinquefolia (L.) Planch.), differing in pigment composition and at different stages of ontogenesis, were studied. Anthocyanin absorption maxima in vivo, as estimated with spectrophotometry of intact anthocyanic versus acyanic leaves and microspectrophotometry of vacuoles in the leaf cross-sections, were found between 537 nm and 542 nm, showing a red shift of 5–20 nm compared with the corresponding maxima in acidic water–methanol extracts. In non-senescent leaves, strong anthocyanin absorption was found between 500 nm and 600 nm (with a 70–80 nm apparent bandwidth). By and large, absorption by anthocyanin in leaves followed a modified form of the Lambert–Beer law, showing a linear trend up to a content of nearly 50 nmol cm⁻², and permitting thereby a non-invasive determination of anthocyanin content. The apparent specific absorption coefficients of anthocyanins at 550 nm showed no substantial dependence on the species. Anthocyanin contribution to total light absorption at 550 nm was followed in maple leaves in the course of autumn senescence. Photoprotection by vacuolar anthocyanins is discussed with special regard to their distribution within a leaf; radiation screening by anthocyanins predominantly localized in the epidermal cells in A. platanoides and C. avellana leaves was also evaluated.

In the studies of lipid metabolism of unicellular photoautotrophic eukaryotes (microalgae), the main attention is commonly paid to polar membrane lipids and their fatty acid (FA) composition, whereas...

An attempt has been made to assess the UV‐B‐protective capacity of phenolic compounds accumulated in superficial structures of plants using apple fruit as a model. Two apple (Malus domestica Borkh.) cultivars (Braeburn and Granny Smith) differing in response to high fluxes of solar radiation were selected and exposed to increasing doses of UV‐B radiation. The extent of UV‐B‐induced damage to photosystem II of apple skin correlated with its quercetin glycoside (but not anthocyanin) content. Granny Smith apples did not demonstrate a pronounced response to high sunlight in terms of the accumulation of phenolic substances in the skin and exhibited similar patterns of F_o, F_m, and F_v/F_m changes in the course of UV‐B irradiation both on sun‐exposed and shaded surfaces of a fruit. Unlike Granny Smith, Braeburn fruits were characterized by a significant accumulation of quercetin glycosides in sun‐exposed skin, however, shaded skin contained these compounds in similar amounts to those in Granny Smith. Accordingly, photosystem II in sun‐exposed skin of Braeburn apples was resistant to high doses of UV‐B radiation (up to 97 kJ m^–2), whereas the susceptibility of the photosynthetic apparatus in shaded skin of Braeburn to UV‐B‐induced damage was much higher and similar to that of both sun‐exposed and shaded skin of Granny Smith fruits. Anthocyanins, at least in the amounts found in Braeburn, did not show an additional effect in UV‐B protection.