Abstract: Objective: To find the best way to reduce the content of stone cells in fragrant pear fruit. Methods: Seven to eight-year-old fragrant pear trees were chosen for foliar application with exogeneous substances including calcium chloride, zinc chloride, boric acid, and salicylic acid. Experiments were conducted using a randomized block design. Key parameters measured included stone cell content, phenylalanine aminase (PAL) and polyphenol oxidase (PPO) activity, sugar content, organic acid content, and color difference. The stone cell clusters were stained using resorcinol. Principal component analysis (PCA) was performed on the different treatment groups. Our aim was to identify the optimal protocol for reducing stone cell content to enhance fruit quality in fragrant pear. Results: Compared with the control group, calcium chloride, boric acid, and salicylic acid significantly reduced the stone cell content in fragrant pear fruit. The stone cell content exhibited a negative correlation with PAL activity: when PAL activity decreased, lignin synthesis was inhibited, leading to reduced stone cell content. The stone cell content showed a nonlinear trend of first increasing and then decreasing with increasing PPO activity. When PPO activity was between 2.5 and 3.0 U/g, the stone cell content was low. Below this range, insufficient lignin polymerization resulted in reduced stone cells, while above this range, excessive lignin polymerization and deposition led to increased stone cells. All four exogeneous substances significantly improved fruit color index, resulting in finer, juicier flesh with better eating quality. Fruits from both 1% calcium chloride and 2% salicylic acid treatment groups exhibited a more spindle-like shape with a fruit shape index of 1.17, better aligning with market preferences. The 2% calcium chloride treatment increased the soluble solids content (SSC) by 10.42% and fructose content by 12.98%, reaching a fructose level of 35.19 mg/g. The 3% boric acid treatment reduced the fructose content by 12.92% compared with the control group, resulting in the lowest value (27.72 mg/g). The 3% salicylic acid treatment significantly increased the glucose content by 16.37%, whereas the 3% boric acid treatment decreased it by 15.87% to 21.29 mg/g relative to the control group. The 2% calcium chloride treatment resulted in the lowest titratable acid level (0.21%), which was 28.09% lower than that of the control group. The 1% calcium chloride treatment gave the lowest citric acid content (147.16 mg/kg), 34.77% lower than that of the control group. All treatments significantly reduced fumaric acid levels, among which the 2% boric acid treatment showed the largest decrease (18.19%) with a final value of 12.06 mg/kg. Conclusion: Foliar spraying of 2% calcium chloride or 3% boric acid could significantly reduce the content of stone cells in fragrant pear fruit, improve fruit color and fruit shape index, increase soluble solids and fructose contents, and reduce titratable acid and citric acid contents, thereby improving fruit quality.

Key words: fragrant pear; stone cells; exogenous substances; quality differences