Purpose Effects of exogenous ABA on the physiology of developing Luffa cylindrica fruits was studied for commercial quality improvement.

Method L. cylindrica (L.) Roem, LZL-2, was sprayed at the flower bud stage with 0 (CK), 2, 4, or 8 mg·mL⁻¹ of ABA. In 0, 3, 6, 9, 12, and 15 d after the application, changes in activities of antioxidant enzymes, i.e., CAT, POD, and SOD, contents of endogenous hormones, i.e., ABA, IAA, GA₃, and ZR, contents of phenolic acids, i.e., PPO, TP, and CA, as well as contents of soluble protein, sucrose, and starch in the fruits formed on the vines were monitored. Correlations between these indicators and the physiological indicators were analyzed.

Result (1) Spraying 8 mg·mL⁻¹ ABA on the plants significantly enhanced the activities of CAT and SOD, but inhibited somewhat that of POD, in the fruits. (2) The applications significantly altered the phenolic acid and sugar compositions. And as ABA in plant increased from the spraying, the contents of PPO and TP became negatively correlated with the fruit development, whereas those of coumaric acid, sucrose, starch, and soluble protein significantly positively correlated. (3) The 8 mg·mL⁻¹ ABA treatment rose the ABA and ZR contents in the fruits. On the 9^th day, transition points appeared where ABA began to decline and ZR to rise, while 4 mg·mL⁻¹ ABA augmented the IAA and GA₃ and significantly correlated with the fruit development.

Conclusion Exposure of L. cylindrica plants to ABA significantly affected its fruit development. Appropriate ABA application, such as spraying at the rate of 8 mg·mL⁻¹, stimulated antioxidant enzyme activity and escalate the contents of phenolic acids, sugars, and endogenous hormones in the fruits to effectively enhance the market value of the vegetable.