Hydrogen-Rich Water Suppresses Dark- and ABA-Induced Postharvest Senescence in Non-Heading Chinese Cabbage (Brassica rapa ssp. chinensis)

Non-heading Chinese cabbage (NHCC) is a highly economically valuable leafy vegetable widely grown in Asian regions. However, it undergoes rapid leaf yellowing and wilting during postharvest storage, which subsequently cause rapid quality decline and loss of nutritional components. Abscisic acid (ABA) promotes postharvest leaf senescence, while hydrogen-rich water (HRW) is widely used in postharvest preservation due to its excellent antioxidant properties; yet, the mechanism through which they interact to regulate postharvest senescence in NHCC remains unclear. Herein we found that exogenous HRW effectively delayed dark- and ABA-induced postharvest leaf senescence in NHCC, significantly maintained chlorophyll content, inhibited oxidative damage, and preserve nutritional components such as soluble sugars and vitamin C. The underlying mechanism was HRW inhibiting chlorophyll degradation by repressing the expression of chlorophyll catabolic genes like NYC1, NYE1, and PPH1. Meanwhile, HRW effectively lowered the accumulation of MDA and H2O2, elevated both the enzymatic activities and transcript abundance of SOD and CAT, and downregulated the transcript levels of RbohB, RbohC, RbohD, and RbohE, thereby maintaining reactive oxygen species (ROS) homeostasis. In addition, HRW negatively regulated ABA biosynthesis by inhibiting the transcript levels of ABA1, ABA2 and ABA3, while promoting the transcription of CYP707A1, CYP707A2 and CYP707A3. It also dampened the transcript abundance of ABA signaling components including PYL5, ABI1, and ABF3, thus blocking ABA signal transduction and alleviating its senescence-promoting effect. Collectively, this study confirms that HRW mitigates leaf senescence induced under dark and ABA conditions in NHCC via multiple synergistic pathways.