Effects Of Light Intensity And Light Quality On The Photosynthetic Characteristics And Morphology Of Soybean Seedlings Under Shade

Under the corn-soybean intercropping system,the high-position crop corn will cause a shady light environment to the low-position crop soybeans.However,the shading is not only the decrease of the light intensity but also the decrease of the red/far-red ration.In order to clarify the response characteristics of the soybean leaf structure and photosynthetic characteristics to different light environments,four different light environments were set with Nandou 12 as the material:1（CK;normal light）,treatment 2（A2;normal light+far-red light）,treatment 3（A3;low light）,treatment 4（A4;far red+low light）.The effects of different light environments on the morphology,leaf structure and photosynthetic characteristics of soybean were studied.The mechanisms of different light environments on the photosynthetic differentially expressed proteins in soybean leaves were analyzed to provide a theoretical basis for improving the yield of soybean.The main test results are as follows:1.Under low light conditions,the plant heights of A2 and A3 soybeans increased significantly,which were 94.54%and 81.20%higher than the CK,respectively.The stem diameters of A2 and A3 were significantly lower than CK,which were reduced by 19.76%and 17.33%,respectively.Low red/far red light ration can increase the petiole length of soybean seedlings.The petiole length of A1 was significantly higher than CK about77.67%,30.97%,35.74%,58.77%.2.Low light and low red/far red light ration make the leaves thinner,and the degree of differentiation in palisade tissue and sponge tissue reduce.A1 palisade tissue and spongy tissue decreased by 17.66%and 10.26%compared with CK.The thickness of A2 palisade tissue and spongy tissue was 46.63%and 62.14%of CK,respectively.A3 palisade tissue differentiation was significantly inhibited,a reduction of 51.73%compared to CK.Low light can significantly change the shape of soybean chloroplasts,reduce the area and number of starch granules,and increase the degree of lamella stacking.Under low red/far red light ration,soybean chloroplast starch grain area increased.3.Under low light and low red/far red light ration conditions,the net photosynthetic rate,stomatal conductance and transpiration rate of soybean leaves showed a downward trend,and intercellular CO₂ increased.Low light conditions,soybean chlorophyll a and chlorophyll a/b are lower than CK.Under low red/far red light ration conditions,the content of chlorophyll b in soybean was higher than that in the control,while that in chlorophyll a/b was smaller than that in the control.PSII maximum photochemical quantum yield,non-photochemical fluorescence quenching coefficient,actual photochemical efficiency in the weak light or low red/far red light ration environment,consistent rules,are smaller than normal light.4.Using isotope labeling relative and absolute quantitative techniques,406 differentially expressed proteins located in chloroplasts were screened out in soybean leaves under different light conditions.Mainly involved in the porphyrin and chlorophyll biosynthesis metabolism pathway,light-harvesting pigment protein complex metabolism pathway,photosynthetic phosphorylation and sucrose starch metabolism pathway.Low light conditions,the original chlorophyllate synthase,ferredoxin,plastocyanin and chlorophyll a/b protein complexes are upregulated.Under low red/far red light ration conditions,the expression of proto-chlorophyllate reductase and light-harvesting pigment protein complex was down-regulated.In the pathway of sucrose starch metabolism,the light intensity weakened the sucrose synthase and particle-bound starch synthase upregulation,while in the low red/far red light conditions,no relevant protein was found.Under shading conditions,the soybean leaves were mainly upregulated in the expression of sucrose synthase involved in sucrose production and the downregulation of glucose-1-phosphate adenylyltransferase that promotes starch production.Based on the above results,the ratio of low light and low red/far red light will regulate soybean morphology,leaf structure,photosynthetic characteristics,and differential expression of proteins in photosynthetic pathways to adapt to changes in the light environment.