Studies on Effects of Polyacrylamide and CO_2 Concentration Variations on Photosynthesis and Water Use Efficiency of Populus euphratica

Experiment was conducted with pot-cultured seedlings of Populus euphratica for studying the enrichment of CO_2 concentration's effect on the photosynthesis and water use efficiency(WUE)under different polyacrylamide content.The results are as follows:(1)With the polyacrylamide content decreased,the soil water suction increased, then drought stress developed.With the water stress increased,leaf water potential,net photosynthetic rate(Pn),water use efficiency,stomatal conductance(Gs)and transpiration rate(Tr)were reduced,the intercellular CO_2 concentration (Ci)was increased.(2)With the CO_2 concentration elevated,the Pn,WUE and Ci increased,but the Tr and Gs decreased.The results we have concluded showed that To some extent the influence of drought stress to Pn and WUE was relieved by the enrichment of CO_2 concentration;The effects of CO_2 concentration enrichment on Pn depend on polyacrylamide content,when it increased,the plants benefited more;When the CO_2 concentration enhanced, the stomata closed and the Tr decreased,so that the WUE increased,which could strengthen the tolerance of Populus euphratica to the drought stress.