Abstract: [Objective] This experiment aimed to explore the effect of exogenous hormones on ornamental and physiological characteristics of Bougainvillea spectabilis, by analyzing the correlation between the flowering process and physiological and biochemical characteristics of the plants subjected to foliar-spraying ethephon (ETH) and paclobutrazol (PP₃₃₃), in order to provide theoretical basis and practical guidance for more effective flowering regulation and improvement of flowering of B. spectabilis in practical production.[Method] The plants were sprayed on leaves with 25, 50, 75, 100, and 125 mg·L^-1 ETH, and 100, 300, 500, 700, and 900 mg·L^-1 PP₃₃₃, and spraying water served as control. The first treatment was started on August 23, 2016, repeatedly spraying every 10 days, three times in total. The changes of ornamental characteristics during plant growth and development were observed and recorded, and at the same time, the contents of endogenous hormones, carbohydrates and soluble protein were measured.[Result] In the early stages of flower bud differentiation, the lower concentration of IAA, GA₃ and higher ABA and ZR levels were favorable for the flower bud differentiation; The higher levels of IAA, relatively stable GA₃, and lower ABA and ZR contents were beneficial to the development of various parts of flower in the late stage of flower differentiation. The total nitrogen content was lower, and the higher concentrations of total soluble sugar and soluble protein content could promote the flowering of plants in the early stage of morphological differentiation. The 75 mg·L^-1 ETH significantly increased the ratios of ABA/IAA, ABA/GA₃, ZR/IAA, and ZR/GA₃, reduced the content of total nitrogen, and promoted the ratio of C/N in the early stage of differentiation. At the same time, the number of flower branches and flowers increased, so that the plant flowering initiation time was 5 days earlier, the whole blooming time was 7 days longer than the control; The ratios of ABA/IAA, ABA/GA₃, ZR/IAA, and ZR/GA₃ and total nitrogen levels were inhibited by 100 mg·L^-1 PP₃₃₃ treatment, and the plant flowering time was delayed for 1 day, the final flowering period was unchanged.[Conclusion] The 75 mg·L^-1 ETH treatment can obviously promote the number of flower branches, flowers, the initial flowering period and the total flowering time, which could be used to promote the growth and flowering of Rhododendron grandiflorum, while PP₃₃₃ treatment could inhibit the growth and flowering of B.spectabilis to some extent.

Key words: Bougainvillea spectabilis, ornamental traits, endogenous hormone, carbohydrates, soluble protein