Effects of waterlogging on net photosynthetic rate,transpiration rate,root activities and potassium contents of tobacco( Nicotiana babacum L.) at different development stages were studied in pot experiments by using split split plot method.The results show that the net photosynthetic rate and transpiration rate are affected the most at root extending phase and decrease by 76.77% and 66.67% respectively when conpared with the control.The activities of roots and the contents of potassium in leaves are more heavily affected by waterlogging at the middle and late growth stages of tobacco.With the ...