Abstract: 【Objective】The present study was conducted to construct three-dimensional(3D) plant virtual model of canopy structure of apple, to provide precise and quantitative method for evaluating canopy structure and light interception of fruit tree and provide data for growers to make proper training and pruning in high density planting systems. 【Method】 Two 14-year-old tall spindle shape of ‘Fuji’ apple with dwarf insterstock were chosen as materials to construct 3D virtual plant model based on 3D digitizing for these trees and measuring morphological indexes of leaves and shoots in a global range of trees. The 3D distribution of leaf area, light interception according to shoot types and fruit yield were studied quantitatively.【Result】The allometric relationship among indexes of shoot and leaf morphology was established. There existed significant linear correlations between shoot length and shoot leaf number, shoot leaf area, respectively, leaf length and petiole length, leaf width, respectively, and the square of leaf length and leaf area. The three-dimensional plant virtual model of apple was constructed by combining 3D digitizing and the allometric relationship between shoot and leaf morphology indexes. For leaf number of shoot and leaf area of shoot between simulated and measured, the coefficient of determination (R²) was 0.92 and 0.95, respectively, root mean square error (RMSE) was 1.18 and 31.5 cm², and relative prediction error (RE) was 7.15% and 5.86%, respectively. The precision of 3D virtual plant model can meet the requirements for analyzing canopy light interception and structure. The model can be used to quantitatively simulate leaf area, volume, projected leaf area, STAR, overcrowded ratio, relative variance of leaf area density (ξ) and diurnal variation of STAR at shoot and tree scale. For tall spindle shape of ‘Fuji’ with dwarf interstock, the shoots mainly distributed in 0.5-2.5 m height and 20-80 cm to trunk in horizontal distance within canopy, 74.88% leaf area was in this zone. The volume and ratio of overcrowded of canopy were 4.47 m³ and 44.62%, respectively. For vegetative short shoot, vegetative long shoot and bourse shoot, the relative volume to whole canopy volume was 69.73%, 43.50% and 41.26%, respectively, the ratio of overcrowded was 60.77%, 54.12% and 83.15%, respectively, the mean STAR value was 0.10, 0.23 and 0.14, respectively, the STAR value increased gradually from bottom to top and also increased from inner to outer of the canopy regardless of shoot types. Yield of fruits mainly distributed in 0.5-2.0 m height and 20-60 cm to trunk in horizontal distance within canopy and was about 4.1×10³ kg per 667m². Diurnal variation of STAR for the whole canopy, vegetative short shoot and bourse shoot was bimodal curve and for vegetative long shoot was unimodal curve. STAR values, no matter which shoot types, had a significant negative correlation with bourse shoot number and had a significant positive correlation with soluble solids, fruit weight and diameter, respectively.【Conclusion】Three-dimensional virtual plant model can be used to evaluate the tree structure and light interception precisely and quantitatively. STAR also can be used to evaluate canopy light interception efficiency quantitatively.

Key words: Fuji apple, virtual plant, tall spindle shape, light interception, STAR