Responses of Photosynthetic Characterization of Kiwifruit(Actinidia chinensis Planch cv.Guihaia 4) Submitted to Shading

Shading is good or not for the plant performance under field environmental conditions,especially for some economic crops and fruit that distribute a large area in the world.To characterize the role of shading on the modulate of the physiology of plant,three levels of shading(full sunlight(0,40%,60% of solar radiation interception) on the photosynthesis and Chl a fluorescence were studied in Kiwifruit(Actinidia chinensis Planch cv.Guihaia 4).The results showed full sunlight treatment resulted in higher Amax,AQY,LSP,LCP and Rd than that of the 40% and 60% shading,while there was no difference between the latter two shading treatments.WUE and Chl content were not affected by the light regime.Pronounced changes for Chl a fluorescence parameters were only found in F′v/F′m,PhiPS2 and qP,under full sunlight and 40% shading,and Fo,Fv,Fm,Fv/Fm did not differ significantly among all the light regimes.Full sunlight resulted in higher qP than 40% shading,while there was no significant difference compared with 60% shading.In conclusion,Kiwifruit under shading did not affect the maximum intrinsic efficiency of photo-system 2(PS2)(Fv/Fm) in these species, suggesting shading had no effect on photosynthesis by inactivation of PS2 reaction centers.Amax,,LSP,LCP,and Rd were reduced when submitted to shading,while there was no difference between the two shading levels,indicating that the Kiwifruit photosynthetic apparatus was prepared to cope with increasing shading levels.Shading did not have large influence on the fruit external appearance,while dramatically affect the fruit quality,as the fruit weight and size were nearly the same(P0.05),but the content of Vitamin C,total sugar content(Reducing sugar and sucrose),soluble solids and the content of acid differed significantly between full sunlight and different shading levels.