Regulatory effects of micronutrient fertilizers on endogenous hormones and pollen quality in camellia oleifera abel (Theaceae)

• Foliar micronutrients increasing ABA/JA/GA4 in flowers and SA/ BL in leaves. • Ca/Mg affected tZR/H2-JA/GA3/BL/MT, and Zn/Cu/B/Mn/Ni/Fe associated with ABA/IAA/IP. • Optimal dilutions (300 × and 600 ×) boost pollen quality and fruit set. In this study, foliar micronutrient spraying was applied during the bud stage in a mature Camellia oleifera Abel (C. oleifera ) forest. The results showed that during the flowering period, the contents of Ca, Zn, Cu, B, and Ni exhibited significant differences among petals, stamens, and receptacles, whereas Mg, Mn, and Fe did not show significant variation. Redundancy analysis revealed that Ca and Mg were primarily positively correlated with H2-JA, GA3, MT, tZR, and BL, with a cumulative contribution rate of 52.61 %, while Zn, Cu, B, Mn, Ni, and Fe were mainly positively associated with ABA, SL, IP, IAA, and IPA, accounting for 47.41 % of the variance. Meanwhile, foliar micronutrient application effectively regulated endogenous hormone levels, particularly increasing ABA, JA, GA4, tZR, IPA, Me-JA, IP, K, and IBA in flowers. In addtion, foliar micronutrient application significantly enhanced pollen viability and germination in C. oleifera , with 300-fold and 600-fold dilutions identified as the optimal concentrations for balanced nutrient absorption. These findings demonstrate that appropriate foliar application of micronutrients substantially enhances pollen quality, offering a practical strategy to improve fruit set in C. oleifera .