Optical properties of different structures of some herbaceous understorey plant species from temperate deciduous forests

Abstract

This contribution discusses the optical properties of different structures of some herbaceous understorey plant species from temperate deciduous and mixed forests. These forests are marked by annual dynamics of radiation level that is related to the vegetation cycle of forest trees. During winter and early spring, the understorey is exposed to full solar radiation, whilelater in the growing season radiation is limited due to the closing of the tree storey. The plasticity of optical properties ofphotosynthetic structures of understorey plants is directly related to their structural and biochemical phenotypic plasticity that optimises harvesting and use of energy. The optimisation of energy harvesting is also achieved by specific adaptations of green leaves, such as variegation (Pulmonaria officinalis, Cyclamen sp.), anthocyanic lower epidermis (Cyclamen sp.), and by using structures other than green leaves for photosynthesis, such as bracts (Hacquetia epipactis) and sepals (Helleborus sp.). The optical properties of these structures are similar to those of green leaves. The understanding of optical responses of different structures contributes to the understanding of the forest understorey functioning.