Tree shape and bearing shoot type jointly drive within-canopy differentiation of fruit quality and mineral element...

Tree shape optimizes canopy architecture; however, its role in regulating within-canopy spatial heterogeneity of fruit quality and the underlying physiological mechanisms remains unclear in jujube (Ziziphus jujuba Mill.). We hypothesized that tree shape drives fruit quality differentiation by restructuring canopy structure, thereby modulating bearing shoot type distribution and mineral element partitioning.

A two-year (2024-2025) field trial was conducted on 15-year-old 'Junzao' trees. Following an initial screening of four tree shapes, the two superior forms-Small-canopy shape (S) and Trunk shape (T)-were selected for in-depth analysis in 2025. Canopies were vertically stratified into upper, middle, and lower layers, and fruits were classified by bearing shoot type (lignified vs. deciduous). Canopy structural parameters (LAI, MTA, DIFN), fruit quality traits (sugars, phenolics, flavonoids), mineral elements (K, Ca, Mg, etc.), and yield components were systematically evaluated.

Optimized tree shapes (S and T) significantly outperformed Open-central shape and unpruned controls in overall fruit quality. Vertically, a distinct trade-off emerged: single-fruit weight and soluble sugars peaked on lignified shoots in the middle canopy (29.08 g, 26.66%), while total flavonoids and phenolics accumulated predominantly in the upper and lower layers. Potassium distribution aligned closely with sugar accumulation, whereas calcium and magnesium were enriched in zones with higher diffuse light penetration (linked to lower LAI and higher DIFN). Deciduous shoots accumulated more mineral elements than lignified shoots within the same layer, suggesting a compensatory uptake mechanism. Notably, the Small-canopy shape increased yield per plant by 31.46%, Grade 1 fruit percentage by 45.05%, and yield per unit area by 40.49% compared to the Trunk shape. PCA clearly separated the two shapes, with mineral elements (K, Ca, Mg) and quality traits (single-fruit weight, total phenolics) serving as key discriminators. Our results demonstrate that tree shape orchestrates within-canopy quality differentiation through structural modulation of canopy light environments and shoot-type composition, which subsequently alters mineral element source-sink partitioning. These findings provide a mechanistic basis for precision pruning strategies aimed at improving fruit uniformity and marketable yield in jujube production.