Effects of Reduced Solar Radiation on Chlorophyll Fluorescence Parameters and Gas Exchange in Winter Wheat of Grain Filling Periods

In the recent years,global dimming of solar irradiance is growing due to the increase of aerosols,air pollutants and population density.In order to elucidate the effects of reduced solar irradiance on chlorophyll fluorescence parameters and gas exchange of winter wheat cultivar,we conducted a field experiment in Nanjing city by using the Triticum aestivum L.(cv.Yang mai 13) as the experimental plants.Five reduced solar radiation treatments were set up in the experiments,including 15%(T4),20%(T3),40%(T2),60%(T1)and 100%(CK)of natural solar radiation,while using Diving-PAM chlorophyll fluorometer and LCpro+ photosynthesis to measured at different grain filling stages of crop chlorophyll fluorescence and gas exchange of the dynamic changes.The results showed that reducing solar radiation significantly increased chlorophyll and lutein content of winter wheat in the grain filling stage,but the Chla/Chlb and photosynthetic rate(Pn) continued to decrease.Fv/Fm,qP,Y(NO),(1-qP)/NPQ and the actual photochemical efficiency(Yield) increased with solar radiation intensity decreased,and show a downward trend,but NPQ,Y(NPQ) and L(PFD) rised.Visible,less solar radiationis cut in winter wheat leaves,when the primary photochemical reaction of PSⅡelectron transfers efficiency met the energy shortage of stress(a decline in photochemical quenching qP).Meanwhile,reducing the electronic delivery of the body(PQ) activity(quantum efficiency Yield was lower),was to increase the heat dissipation leaves,resulting in reduced photosynthetic capacity.