Effects of leaf age on internal CO2 transfer conductance and photosynthesis in tree species having different types of shoot phenology

We examined the changes in leaf anatomy and some physiological characteristics during leaf expansion and maturation. Three deciduous tree species having different types of shoot phenology, maple (Acer mono Maxim.; 'flush' type), alder (Alnus japonica (Thunb.) Steud.; 'successive' type), and Japanese poplar (Populus maximowiczii A. Henry; 'successive' type), were studied. Leaf CO2 assimilation rate at high irradiance (P-max) and CO2 transfer conductance inside the leaf (g(i)) varied significantly with leaf development. There were strong positive relationships between P-max and g(i) for all of the species. The variations in g(i) were partly related to those in the surface area of chloroplasts facing the intercellular airspaces, while some other factors that related to liquid phase conductance may also contribute to the variation in g(i). The developments of mesophyll cells were accompanied by the concomitant increase in chloroplast and Rubisco content in Alnus and Populus (successive types).