Mechanism of leaf coloration in Acer henryi Pax based on non-targeted metabolomics

This study investigated the physiological and metabolic mechanisms associated with autumn foliar coloration in Acer henryi Pax. Leaves representing successive autumn color stages were collected and analyzed for leaf structure, color parameters, pigment content, physiological indicators (soluble sugars, soluble proteins, mineral elements), and global metabolite profiles. During the transition from green to red and subsequently to yellow leaves, chlorophyll content significantly decreased by 95.45%, whereas anthocyanin content reached a maximum at the red-leaf stage (T5, 35.02 U/g). Carotenoid content and the carotenoid/chlorophyll ratio increased progressively. Leaf thickness, total nitrogen, and total phosphorus declined during coloration, whereas soluble sugar and soluble protein contents peaked at the red-leaf stage (T5) and showed significant positive correlations with anthocyanin accumulation (P<0.05). Non-targeted metabolomics identified 35 significantly altered metabolites, with flavonoids such as catechin, delphinidin, and quercetin representing key compounds associated with leaf color development. Quercetin was also positively correlated with anthocyanin glycosides (P<0.05). KEGG enrichment analysis further identified flavonoid biosynthesis as the principal metabolic pathway underlying autumn coloration.