Effects of different soil moisture treatments on physiological characteristics of summer maize leaves

By imposing different lower limits of soil moisture on summer maize(Zea mays L.)grown in non-weighting lysimeters under a rain shelter,the effects of soil water status on physiological characteristics and water use efficiency of summer maize were studied.The results showed that all the physiological parameters had obviously diurnal change characteristics;the time when the maximum of stomatal conductance(Gs) appeared was earlier than that of photosynthetic rate(Pn) and transpiration rate(Tr).Under high soil water condition(T-80),the time when the peak value of Tr emerged was later than that of Pn, but the time when the peak value of Tr in both T-60 and T-50 treatments emerged was earlier than that of Pn.The maximum of Gs,Tr and Pn appeared to become earlier with soil moisture decreasing,and the peak values of leaf water potential(LWP) and cell sap concentration(CSC) were all appeared at about 14∶00 pm.Gs,Tr,Pn and LWP increased with the improvement of soil water,but the CSC declined.Leaf water use efficiency(LWUE) increased with the augmentation of photosynthetic active radiation(PAR) and reached the maximum at about 10∶00 am.The LWUE of T-70 treatment was the highest and that of T-50 was the smallest.In addition,according to the results of yield and water use efficiency in different treatments,the proper lower limit of soil moisture for water-saving and high-yield in summer maize was 70% of field water capacity.