Effect of Doubled Atmospheric CO_2 and Nitrogen Application on Photosynthetic Rate and Chlorophyll Fluorescence Character of Winter Wheat

The experiment was conducted to investigate the effect of doubled atmospheric CO2 concentration,nitrogen application on the photosynthetic rate and chlorophyll content and fluorescence parameters of two winter wheat cultivars with pot-culturing method in Open Top Chamber(OTCs).The result showed that under elevated atmospheric CO2 concentration,the photosynthetic acclimation appeared in wheat leaves of no nitrogen application but the photosynthetic acclimation did not appear in wheat leaves of nitrogen application.Compared with the background CO2 concentration(375 μmol·mol-1),doubled CO2(750 μmol·mol-1) significantly reduced the leaf chlorophyll content,Fm,Fv,Fv/Fm and Fv/F0 values,and increased F0 value of two wheat cultivars at the four stages of jointing,booting,anthesis and middle grain-filling.Nitrogen application could evidently increase the leaf chlorophyll content,Fm,Fv,and Fv /F0 values,and decreased F0 values of two wheat cultivars at the four stages.The effects of doubled CO2 concentration on the leaf chlorophyll content and fluorescence parameters of wheat cultivars were significant at the 0.05 level under no nitrogen application,whereas were indistinct under nitrogen.Therefore,the doubling of atmospheric CO2 concentration would inhabit leaf photosynthetic rate,chlorophyll content,the photosynthetic electron transport and the potential activity of PSⅡ of winter wheat,while nitrogen application could eliminate its effects.