Response of water stress on photosynthetic characteristics and water use efficiency of maize leaves in different growth stage

The field experiments of water stress and rewatering for maize were carried out using the large moving water-proof shed. The effects of water stress on the photosynthetic characteristics and water use efficiency of maize in different growth stages were revealed by the photosynthetic data of leaves. The results showed as followed: water stress led to the decrease of the values of photosynthesis rate,transpiration rate and stomatal conductance and the earlier emergence of peak value of the daily variation of photosynthesis. Compared with the control,the transpiration rate,photosynthesis rate and stomatal conductance of maize leaves were decreased significantly,in order to adapt to the drought under the water stress condition so that the water use efficiency was improved and the difference of water use efficiency between the water stress and normal condition was shrunk. Under moderate or severe water stress condition,the decrease of water use efficiency was less than that of the photosynthesis,transpiration rate and stomatal conductance of maize leaves and the water use efficiency was sometimes even higher than that of the normal environment. The water use efficiency of maize leaves was improved under moderate water stress so that the ability of leaf using water was enhanced and maize better resisted drought environment; the subsequent effects of water stress on photosynthesis and transpiration and water use efficiency was obvious. After waterstress and rewater treatments,the inhibition of photosynthesis of maize leaves was still continued. Longer time and more severe the water stress was,the more nonreversible the photosynthesis of maize leaves might be. The inhibition of water stress on photosynthesis of maize leaves was more difficult to recovery from the jointing to silk stage than from three leaf to jointing stage.