Effects of elevated NH3 on the photosynthetic physiological characteristics in winter wheat leaf with various N levels.

The experiment was carried out in Open Top Chamber(OTCs).The main aim of this study was to investigate the response of various photosynthesis parameters,e.g.,net photosynthetic rate(Pn),stomatal conductance(Gs),chlorophyll content,chlorophyll fluorescence characteristics(Fv/Fm、Fv/F0) and soluble sugar content in two wheat cultivar types to elevated NH3 concentration.The results showed that:The value of Fv/Fm had no significant change in treatments.In the High NH3+Low N treatment,the values of Pn,Fv/F0 and soluble sugar were higher than those both of High NH3+High N and Low NH3+Low N treatments(especially in the late growth stage).The value of Gs was also according above regularity only in nitrogen inefficiency crop,and the difference of different treatments was significant(P0.05).In the High NH3+High N treatment,the value of Pn was all significantly(P0.05) lower than those in the Low NH3+High N treatment at every growth stage.However,it appeared at filling stage for chlorophyll content and before filling stage for soluble sugar content.But the difference of photosynthesis parameters between crop types was no obvious.All these results suggest that increased atmospheric NH3 can enhance the status of nitrogen nutrition of winter wheat growing in low N medium,but the result of being more significantly positive effect on low nitrogen efficiency cultivar still need further study.