Research Of Reduced Solar Radiation On Photosynthesis And Fluorescence Characteristics Of Winter Wheat Under The Stress Of Increased O₃Concentration

Aerosol is currently one of the major environmental issues of concern to the world, and atmospheric aerosol through direct or indirect effects to affect crop photosynthetic capacity decreased, which led to the reduction of crop yield; But in the context of environmental change in the future, the surface concentration of O3showed a continuous increase trend has strong negative effects on crop growth and metabolic process, which will be a direct threat to the food crops security. In order to further prove the effects increase in surface O3concentration and atmospheric aerosols generated by solar radiation attenuation on crop photosynthesis and fluorescence characteristics of impact mechanism. This study, in the field experiment conditions by using a completely randomized grouping method, set (CK, OTC without ozone and shading net), T1(80%natural light), T2(60%natural light), T3(40%natural light) and T4(100nL·L-1O3), T5(80%natural light and100nL·L-1O3), T6(60%natural light and100nL·L-1O3), T7(40%natural light and100nL·L-1O3)8different reduced solar radiation and high concentrations of ozone treatments. On the growth of Winter Wheat in field weakening solar radiation and ozone fumigation treatments, systematic research the effects of the solar radiation attenuated and high concentration of O3on winter wheat photosynthesis, chlorophyll fluorescence parameters, light response curve effect and mechanism for the prevention and control of atmospheric aerosols and high concentration of O3on agricultural production in China and provide scientific basis. Main conclusions are as follows:(1)The increased O3concentration and reduced solar radiation significantly reduced photosynthetic pigment content in winter wheat leaves in each treatment group at the growth stage, and increased dissipation pigment especially lutein increased obviously, to better adaptive growth by increasing the xanthophyll cycle in adversity.(2)Reduced solar radiation and high O3concentration significantly decreased photosynthetic rate (Pn), Gs, Ls, in each treatment group but Ci in each group was significantly elevated contrasted to CK. the WUE of T1-T2treatment groups were higher than CK in the jointing stage and T3-T4significantly reduced; In heading stage T1-T3significantly increased contrast to CK, T4was lower than CK. WUE of T5-T7treatments in jointing and heading stage were significantly increased compared with CK. The above shows, reduced solar radiation and high concentration of O3all significantly reduced winter wheat photosynthetic capacity in early growth period, but increased the WUE at different degrees. High concentration O3significantly inhibited the WUE of Winter Wheat Leaves.(3)Reduced Solar radiation and high concentration ozone decreased qP, Y (NO), the actual light quantum efficiency (Yield), initial slope, Ik, but the (1-qP)/NPQ, NPQ and Y (NPQ) significantly increased compared with CK. Under the stress of solar radiation attenuation and high concentration ozone, winter wheat leaves would by PSⅡ primary photochemical reactions of electron transfer efficiency to meet the energy deficiency stress (photochemical quenching coefficient qP decline), while increasing the heat dissipation capabilities (leaf xanthophyll cycle increased, NPQ and Y (NPQ) significantly increased adapt to adversity.(4) The absorbed light energy distribution direction in winter wheat leaves also produced marked change under the stress of reduced solar radiation and high concentration ozone. Light energy which T1-T4treatments group absorp shifted from D to E, but T5-T7treatments group gradually shifted from E to D in order to better adapt to adversity.