Objective This study aimed to investigate the effects of fruit load on the yield and quality of persimmon (Diospyros kaki Thunb.), and to identify the optimal fruit thinning intensity that balances high yield, superior quality, and sustained tree vigor. The findings provide a theoretical foundation for effective fruit load regulation.

Methods The experiment was conducted using 15-year-old persimmon cultivar, 'Pinghewu'. Five fruit load levels were established by thinning: T1, T2, T3, T4, and CK (control, no thinning), corresponding to 1.2, 1.8, 2.4, 3.0, and 3.6 fruits·cm⁻², respectively. Leaf morphological traits, photosynthetic pigment content, photosynthates, photosynthetic efficiency, chlorophyll fluorescence, fruit yield, and quality indices were measured to analyze the effects of different fruit loads on yield, and quality as well as the underlying physiological regulatory mechanisms.

Result ① Fruit load significantly affected leaf morphology. Compared to the CK group (excessive fruit load), thinning treatments improved leaf length, width, and area with the most significant improvements observed under T2 and T3. ② The effects of fruit load on photosynthetic pigment content varied across treatments. Under the T1 treatment, it showed the highest Chlorophyll a/Chlorophyll b ratio and carotenoid content, while under the CK treatment, it had the highest total chlorophyll (chlorophyll a + b) content. Additionally, under the T1 treatment, it showed significantly higher levels of non-structural carbohydrates and vitamin C compared to other treatments. ③ Photosynthetic parameters (Pn, WUE, and Ci) under T1 treatment were significantly higher than those under other treatments, indicating a higher photosynthetic rate. With increasing fruit load, Fv/Fo, Fv/Fm, ΦPSII, and qP initially decreased and then increased, while NPQ showed a decreasing trend. ④ All thinning treatments improved fruit setting rate, but only T1 treatment significantly increased yield per plant. Average yield per tree increased from 36.11 ± 2.35 kg in CK to 49.00 ± 1.22 kg in T1. Fruit load had no significant effect on individual fruit size, weight, or soluble solid content.

Conclusion Appropriate fruit load regulation significantly affects leaf morphology, photosynthetic physiological traits, and yield performance in persimmon trees. The T1 treatment (1.20 ± 0.18 fruits·cm⁻²) was effective in enhancing leaf photosynthetic efficiency and carbon assimilation capacity, promoting nutrient accumulation, and improving both fruit setting rate and yield per tree. This thinning intensity represents an optimal strategy for balancing productivity and quality in persimmon cultivation.