Impacts Of Canopy Shapes On Canopy Structure,Light Interception And Photosynthetic Capacities For Pergola Trellis Grapevines Based On Digitizing And Modelling

Canopy of grape affects the microclimate and leaf photosynthesis by manipulating light interception and distribution within canopy,and finally determines grape yield and quality.At present,most studies on grape canopy structure are mainly based on field measurements,and which has poor repeatability and lack of dynamic understanding of canopy structure and leaf photosynthesis during growing season.In this experiment,the grape cultivar’Zixiang seedless’in Shihezi region were trained as pergola but with‘厂shape’canopy,bird wing shape canopy and original horizontal shape canopy,respectively.Then,three-dimensional（3D）virtual plant models of grape canopies with different shapes were reconstructed and photosynthetic capacities within canopy were measured in varied canopy locations in filed at different developmental stages,respectively,to evaluate quantitatively the light interception and photosynthetic characteristics.At the same time,fruit yield and quality were comprehensively evaluated.The results obtained will provide deep insight into the canopy structure of canopy and benefit the selection and optimization of canopy structure in the northern Xinjiang region.The main results are as follows:1.By combining in-situ 3D digitizing and allometric relationships among leaf morphological traits,3D virtual canopy with different canopy shapes at different phenological stages was constructed.The model can accurately simulate canopy leaf area,and the virtual canopy can accurately reflect the characteristics of leaf distribution and canopy structure in field.For‘bird wing shape’canopy,the determining coefficient（R²）,root mean square error（RMSE）and relative error（RE）between observed and modelled leaf area were 0.9946,5.42 cm² and 2.41%,respectively.These values in‘厂shape’canopy were R²=0.9937,RMSE=4.84 cm²,and RE=4.59%,respectively,and in original‘horizontal shape’canopy were R²=0.9988,RMSE=4.70cm² and RE=2.35%,respectively.The modelled accuracy can meet the needs of constructing virtual plants.2.The STAR estimated based on 3D virtual plant model has a high correlation with the measured relative light intensity（R²≥0.866）,which can be used for light interception efficiency analysis.The STAR value of the primary shoot was greater than that of the secondary shoot.From flowering stage to maturity stage,except the decrease in STAR of primary shoot of‘horizontal’canopy,STAR of primary shoot,secondary shoot and the whole canopy for all treatments increased.In the mature stage,the canopy STAR of‘bird wing shape’canopy was 32%and 44%greater than the‘厂shape’and the original‘horizontal’canopy,respectively.3.The net photosynthesis rate,stomatal conductance,intercellular carbon dioxide（CO₂）concentration and intercellular CO₂ compensation concentration in‘bird wing shape’canopy were similar than that in‘厂shape’canopy,but significantly higher than that in original‘horizontal’canopy.In‘bird wing shape’canopy,its apparent quantum efficiency,maximum photosynthesis rate were significantly higher than that in the other two canopies.Meanwhile,leaves in the‘bird wing shape’canopy had the lowest light compensation point,initial carboxylation rate,photorespiration rate,dark respiration and transpiration rate,while the other two had similar initial carboxylation rate,photorespiration rate and transpiration rate and the leaves in‘厂shape’canopy had lower light compensation point and dark respiration that‘horizontal’canopy.The photosynthetic capacity of leaves at the top of canopy was better than those at the middle and inner canopy,irrespective of canopy shape.4.The yield per unit area,cluster weight,single fruit weight,soluble solid content and soluble sugar content in‘bird wing shape’canopy were similar with those values in‘厂shape’canopy,but significantly higher than those in‘horizontal’canopy.At the same time,the content of titratable acid was significantly reduced in the‘bird wing shape’canopy compared to the other two canopies.In conclusion,the application of‘bird wing shape’training in grape canopy can significantly improve the light interception efficiency and photosynthetic capacity,as well as the fruit yield and quality.This kind of‘bird wing shape’canopy has the highest potential to increase fruit yield and quality in Northern Xinjiang.