Abstract: Studies on photosynthetic physio-ecological characteristisc of Juglans mandshurica,Fraxinus mandshurica, Betula phatyphylla Tilia amurensis and Phellodendron amurense show that photosynthetic capacity and nitrate reductase activity of different tree speciesare increased with increasing young leaves growth and chlorophyll content. In clear days,the diurnal patterns of B. platyphylla and F.mandshurica photosynthesis show a two-peak, and other three species one-peak, but on the contrary in clear days after overcast and rainy. In cloudy days, the photosynthesis curves of five species are similar to light in tensity ones. Nitrate reductase activity is positively correlated with the photosyntheticrate during yound leaves growing. The relative air humidity is a limiting factor for utilizing light energy except for the influence of light on the photosynthetic rate of different species.

Key words: Juglans mandshurica, Fraxinus mandshurica, Photosynthetic rate, Chlorophyll content, Nitrate reductase activity