Diurnal changes in photosynthetic characteristics of shade adapted medicinal plants grown under open sunlight and shade condition

Five commercially important medicinal plants viz Adhatoda beddomei C.B. Clark Adhatoda vasica Nees, Alpinia galanga S.W., Plumbago rosea Linn, Strobilanthus heyneanus Nees were grown under open sunlight and 70% shade conditions. Diurnal variations in rates of photosynthesis, stomatal conductance and transpiration were observed in the field under open and shaded condition in nine month old potted plants. Maximum Pn was observed for a short period in open sunlight for all the species around 9.00 or 10.00 h whereas peak Pn under shade continued for 3 to 4 hours even at mid day. The adaptability of species to shade is also discussed.