Ontogenetic and seasonal variation in leaf traits regulates flavonoid accumulation and antioxidant capacity in Ormosia henryi prain

Understanding how plants regulate bioactive compound accumulation across ontogenetic stages and seasons is essential for optimizing functional biomass production. Ormosia henryi Prain, a woody legume with high leaf flavonoid content, represents a promising candidate for natural antioxidant resource development. However, optimal strategies for maximizing flavonoid yield across developmental stages and seasons remain unclear. In this study, we quantified variation in leaf structural traits, nutrient stoichiometry, and secondary metabolites across ontogenetic stages and seasonal conditions in O. henryi . Plant trait networks (PTN) and partial least squares structural equation modeling (PLS-SEM) were used to explore trait coordination and its relationships with flavonoid accumulation. Results showed a coordinated shift from acquisitive to conservative strategies during ontogeny, accompanied by progressive nutrient limitation and increased carbon accumulation. Nutrient stoichiometry shifted from nitrogen limitation in early stages to phosphorus limitation in later stages, while potassium limitation persisted throughout development. Compared with spring, autumn was associated with higher carbon concentration, nutrient resorption, and greater secondary metabolite accumulation. Flavonoid accumulation exhibited a unimodal ontogenetic pattern, peaking at intermediate developmental stages (age class 20), with higher levels observed in autumn. These patterns indicate a clear stage–season window for maximizing flavonoid yield and antioxidant capacity. Among the identified compounds, quercetin and diosmetin were strongly associated with antioxidant activities (DPPH, ABTS, and FRAP), whereas leaf pH was weakly but significantly associated with flavonoid accumulation. Overall, intermediate ontogenetic stages under autumn conditions represent the most favorable harvest window for producing flavonoid-rich antioxidant biomass. These results provide new insights into trait–metabolite coordination and offer a practical basis for the sustainable utilization of O. henryi as a functional biomass resource.