Effects Of Shading On Gas Exchange And Chlorophyll Fluorescence Parameters In Leaves Of Rice

The experiment was carried out in potted plant base of Shenyang Agricultural University in 2015.Shennong265,Shennong9816,Liaoxingl and LG0915,were shaded with 50%interception of photosynthetically active photon flux density for 15 days within different growth stages such as tillering stage and heading stage.It was used to research the effects of shading on the gas exchange,chlorophyll fluorescence parameters,yield and quality to find out the regularity of effects of shading on the photosynthetic response mechanism.The mainly results were as follows:1.The chlorophyll content of leaf increased significantly,the Pn and WUE significantly or extremely significantly reduced by shading at different stages.The apparent mesophyll conductance(Gs)and intercellular CO2 concentration(Ci)significantly increased.Meanwhile,the transpiration rate(E)significantly reduced by shading at tillering stages.These show that stomatal factors result in the decrease of Pn by shading at tillering stage.The Gs significantly reduced.The Ci of shennong265 and Liaoxingl leaves were increased,the Ci of shennong9816 significantly reduced,and the Ci of LG0915 was no significant difference with control.Re-illuminated for a short period of time,the net photosynthesis rate(Pn)have no significant difference compared with control.These results indicate that photosynthesis of experimental rice was not affected by irreversible damage under 50%shading treatment2.The maximal quantum yield(Fv/Fm),photochemical quenching of chlorophyll fluorescence(qP),photochemical efficiency light(Fv'VFm')and actual photochemical efficiency(?PS ?)increased significantly,and the electron transport rate(ETR)and non-photochemical quenching of chlorophyll fluorescence(qN)significantly reduced by shading at different stages.,the qN significantly increased under re-illuminated for a short period of time.Leaf improves protection mechanism to adapt the intense light.As the re-illumination time goes,the effects of shading were gradually weakened and disappear.3.The dry matter weight per plant and specific leaf weight were reduced significantly,and dry matter partition of leaves was increased by shading at different stages.The thickness of leaves becomes to be thin and the leaf area increased to get much more light.There were no significant difference in rice yield under shading at tillering stage,but seed setting rate of rice,the head rice rate and chalky rice rate increased significantly in shennong265.Meanwhile,the thousand seed weight,chalky rice rate and chalkiness of Liaoxingl increased significantly.The grain number per panicle of LG0915 was increased,while the head rice rate and chalkiness was reduced by shading at tillering stage.There were no significant difference in dry matter partition of panicle under shading at heading stage.The yield of LG0915 was reduced remarkable by shading at heading stage,and seed setting rate of shennong265,shennong9816 and LG0915 reduced significantly.The milling,appearance and nutrient quality of shennong265,shennong9816 and Liaoxingl were remarkable influenced by shading at heading stage,as well as nutrient quality of LG0915 was effected.