Harvest stage-dependent metabolic and anatomical traits underlying vase life variation in cut hydrangea cultivars

Harvest stage influences postharvest longevity in cut hydrangea, but the traits associated with cultivar-dependent variation remain insufficiently understood. This study evaluated vase life, total soluble and reducing sugar contents, secondary metabolites, and sepal anatomy in eight Hydrangea macrophylla cultivars at fresh and antique stages. Vase life was significantly longer at the antique stage in six cultivars, particularly ‘Royal King’, ‘Royal Parade’, ‘Royal Princess’, and ‘Royal Surprise’, whereas ‘Royal Benefit’ and ‘Royal Anastasia’ showed no significant differences between stages. Total soluble and reducing sugar contents, as well as secondary metabolite profiles, varied among cultivars and harvest stages, with chlorogenic acid and kaempferol 3-O-sophoroside contributing to biochemical variation. Antique-stage sepals generally exhibited lower stomatal density, larger epidermal cells, and thicker epidermal and mesophyll tissues. Longer vase life was associated with lower abaxial stomatal density and stomatal index, as well as greater epidermal and mesophyll thickness, whereas total soluble and reducing sugar contents were not significantly correlated with vase life. Principal component analysis (PCA) differentiated cultivar–stage combinations based on integrated biochemical and anatomical profiles. Phenolic compounds, including afzelin, chlorogenic acid, and neochlorogenic acid, together with anthocyanins, reducing sugar content, stomatal traits, and tissue thickness, contributed to multivariate differentiation. These findings indicate that postharvest longevity is associated with a combination of developmental, anatomical, and biochemical traits rather than carbohydrate content alone, providing insights relevant to cultivar selection and harvest-stage management.