Abstract:Measurements were made of photosynthesis-light response curves, leaf stomatalconductance, intercellular CO2 concentration, water use efficiency (WUE), chlorophyll andnitrogen contents in leaves of 2-to 3-year old seedlings of Betula pendula, Fagus sylvaticaand Quercus robur potted under two contrasting light (full light and 20% full light) regimesin indoor condition in Germany in September, 1989. Regression relationship between netphotosynthetic rate and chlorophyll content was also analysed .The seedlings grown under 20％ full light condition showed a lower net photosynthetic rate and light-saturated point，lower stomatal conduetance and WUE，lower chlorophyll content per fresh weight unit of leaf and the reduced accumulation of dry matter compared to those grown under full light．A positive correlation was found between chlorophyl content and net photosynthetic rate．Seedlings of the three examined tree species could deal well with the shadiness under forest．Betula pendula and Quercus robur would be more capable of adaptation to shady environment than Fagus sylvatica．