Botany
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Item Seasonal changes in organic carbon content of leaves of deciduous trees(Elsevier, 1991) Jayasekera, R.; Schleser, G.H.Changes in organic carbon content were investigated during the course of one growing season in the leaves of beech (Fagus sylvaticaL.) and oak (Quercus robur L.). Considerable alterations in leaf carbon content were found not only during the course of the growing season, but also as a function of tree height. Until about August, leaf carbon content of oak gradually increased and then showed a decline as the leaves yellowed in October. In beech sun leaves there was a gradual increase in organic carbon content with increasing foliage age, whereas shade leaves showed the opposite trend. The results demonstrate that leaf carbon content may vary during leaf ontogenesis, and that the character of ontogenetic changes in carbon content depends not only on plant species but also on canopy position.Item Seasonal changes in potential net photosynthesis of sun and shade leaves of Fagus sylvatica L.(Elsevier, 1988) Jayasekera, R.; Schleser, G.H.Sun and shade leaves of the deciduous tree, Fagus sylvatica, were investigated for their potential photosynthetic activity during the course of one growing season. During the initial period of leaf development and expansion, sun leaves exhibited relatively higher photosynthetic rates. After full expansion of leaves, shade leaves had a higher activity in potential net photosynthesis until about the end of August. Low diffusion resistance for CO2/O2 and higher activities of photosystems in shade leaves seem to be the main causes of their higher photosynthetic potential.