Effects Of Shading On Morphological Characters, Yield And Photosynthetic Characteristics Of Soybean At Different Growth Stages

Intercropping and relay-intercropping are important technologies to improve the utilization of land and promote the yield of crop, but the yield of intercropped and relay-intercropped soybean is limited by shading, and intercropped soybean and relay-intercropped soybean are shaded at different growth stages. To clear the effect of shading at different growth stages on morphology and yield of soybean, Guixia2, Nandou12, Nandongkang22, E61and C103were shaded with the50%transmittance shade net with the natural light as control. The main results showed as follows:1Effects of shading on morphology and yield at different growth stages. shading had a significant influence on the length of main stem and main stem length/stem diameter et al during the early growth period (VER1and VER2), compared with control, the main stem length and main stem length/stem diameter were increased by45.75%and93.64%respectively, shading had significant influence on the number of branches and the height of lowest pod at the late growth stages (R1R8and R2R8), compared with control, the number of branches was decreased by29.97%and the height of lowest pod was increased by28.59%; the cultivars with R/V below1.4was affected large-scalely by the early growth period shading, the cultivars with R/V equal or greater than1.5was easily affected by the late growth stage shading; main stem length, first internode length, branch height, stem length/stem diameter and stem length/branch number were negative and significantly correlated with yield per plant, branch number were positively and significantly correlated with yield per plant, main stem length/stem diameter and main stem length/branch number were key factors for yield per plant.2Effects of shading on quality at different growth stages. the protein content of soybean grain is increased and the crude fat content of soybean grain is decreased by shading, the protein content and crude fat content of soybean grain was affected large-scalely by the late growth period shading, compared with control, the protein content of R1R8, R2R8and R5R8was increased by9.20%,8.98%and6.23%respectively, and the crude fat content of soybean grain was decreased by9.31%,10.74%and4.28%respectively 3Photosynthetic characteristics and its related indexes of different treatments during shading. leaf area was increased and specific leaf weight was decreased by shading, the leaf area and specific leaf weight of soybean grain was affected large-scalely by the early growth period shading; palisade tissue thickness and leaf thickness were increased by shading, but the ratio of palisade tissue thickness and leaf thickness was decreased by shading, the anatomical structures were affected large-scalely by the late growth period shading; light saturation point, light compensation point and maximum photosynthetic rate were decreased by shading, and apparent quantum efficiency was increased by shading, the photosynthetic parameters were easily affected by early growth period shading; the antioxidant enzymes activities were increased by shading, and they were easily affected by early growth period.4Photosynthetic characteristics and its related indexes of different treatments after reilluminated. the earlier reillumination, the less the difference between the anatomical structures and the control, the earlier soybean was reilluminated, the less the difference between the specific leaf weight and the control; the difference between the contents of chlorophyll (a+b) and Chlorophyll a/b and the contents of the control were larger by reilluminated at V5(VER5) stage respectively, light saturation point, light compensation point and maximum photosynthetic rate were increased, but they were less than control yet, and apparent quantum efficiency was decreased by reilluminated at R2stage; the differences of the antioxidant enzymes activities between the treatment reilluminated at R2stage and control were larger than that between the treatment reilluminated at R5stage and control, compared with control, the activities of SOD, POD and CAT were increased by28.76%,22.94%,14.91%by reilluminated at R2stage, but compared with control, the activities of SOD, POD and CAT were increased by42.94%,30.03%,25.17%by reilluminated at R5stage.