为了明确外源处理吲哚乙酸（Indole Acetic Acid, IAA）对采后上海青的影响，该文以蒸馏水为对照组，研究了外源IAA处理后上海青衰老过程中叶绿素含量变化、叶绿素代谢相关基因表达及酶活、IAA代谢途径相关基因表达、内源激素含量变化和抗氧化相关基因表达及酶活，研究发现，外源施加质量浓度为2 mg/L的IAA能够有效维持采后上海青的色泽品质和延缓其叶片衰老，主要通过降低叶绿素代谢相关基因表达（BrNYC1、BrNOL、BrPPH、BrPAO、BrSGR1和BrSRG2）和酶活（PPH、PAO和MDcase）来延缓叶绿素的降解。同时，IAA能够调控生长素信号转导途径相关基因（BrARF2、BrARF7、BrARF19、BrGH3.5、BrGH3.12和BrGH3.17）的表达以维持采后上海青内源IAA的含量。此外，IAA可以提高抗氧化代谢相关基因（BrCAT、BrPOD和BrSOD）的表达来增加过氧化氢酶（Catalase, CAT）、超过氧化物酶（Peroxidase, POD）和氧化物歧化酶（Superoxide Dismutase, SOD）抗氧化酶活性，增强采后上海青的抗氧化性。综上，外源IAA可有效保持上海青的色泽品质，延缓其叶片衰老，该研究结果将为上海青采后技术的开发提供依据。

In order to clarify the effects of exogenously applied indoleacetic acid (IAA) on postharvest pak choi and the mechanism of the effects, changes in chlorophyll content, chlorophyll metabolism-related gene expression and enzyme activities, IAA metabolic pathway-related gene expression, endogenous hormone content, and antioxidant-related gene expression and enzyme activities during postharvest pak choi senescence were investigated using distilled water spraying as a control group in this experiment. It was found that the colour quality of postharvest pak choi was effectively maintained and its leaf senescence was delayed by exogenous application of 2 mg/L IAA, mainly by reducing the expression of chlorophyll metabolism related genes (BrNYC1, BrNOL, BrPPH, BrPAO, BrSGR1, and BrSRG2) and enzyme activities (PPH, PAO, and MDcase) to delay the degradation of chlorophyll. Meanwhile, the expression of growth hormone signalling transduction pathway-related genes (BrARF2, BrARF7, BrARF19, BrGH3.5, BrGH3.12, and BrGH3.17) could be regulated by IAA to maintain endogenous IAA content in postharvest pak choi. In addition, the expression of antioxidant metabolism related genes (BrCAT, BrPOD, and BrSOD) was enhanced by IAA treatment to increase the antioxidant enzyme activities of catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD) and enhance the antioxidant properties of postharvest pak choi. In conclusion, exogenous IAA can effectively maintain the colour quality of pak choi and delay its leaf senescence, and the results of this study will provide a basis for the development of postharvest technology for pak choi.