The Influence of Exogenous Hormones 6-BA and GA₃ on the Flowering Period of <italic>Chionanthus retusus</italic> ‘Chunxue’

To investigate the effects of exogenous hormones 6-BA and GA3 on the physiological and biochemical processes of Chionanthus retusus Lindley & Paxton, as well as their impact on flowering period, the experiment utilized the early-flowering cultivar C. retusus ‘Chunxue’ as the test material. Exogenous hormones 6-BA and GA3 were applied using a foliar spray method, with five concentration gradients set at 100, 200, 300, 400, and 500 mg/L, using equal amounts of water spray as the control group (CK). Sampling was conducted during the flowering period to measure soluble sugar, soluble protein, antioxidant enzymes (SOD, POD, CAT), and endogenous hormones (IAA, GA3, ABA, ZR). The results indicated that treatments with both 6-BA and GA3 significantly reduced the content of soluble sugars during the flowering period. An increase in the concentration of 6-BA corresponded with a decrease in soluble protein content in the leaves, while low concentrations of GA3 promoted protein accumulation prior flowering, and high concentrations inhibited it. Both hormones were effective in delaying the decline of antioxidant enzyme activity, with low concentrations of 6-BA and GA3 enhancing the activities of CAT and POD. Applying appropriate concentrations of 6-BA and GA3 was beneficial in extending the flowering period; notably, a concentration of 400 mg/L of 6-BA advanced the flowering period while extending it by a total of 6 d, and concentrations of 200 mg/L and 300 mg/L GA3 extended the period by 7 d and 9 d, respectively. This study provides a theoretical and technical basis for the selection and cultivation of superior cultivars of C.retusus and for the regulation of flowering time.