Flower bud differentiation and leaf endogenous hormone changes of Camellia perpetua

Camellia perpetua is the only rare and endangered plant in the genus Camellia that blooms almost all year round. In order to explore the flower bud differentiation process and the changes of endogenous hormones in leaves at different flower development periods and annual growth cycles, the process of C. perpetua flower bud differentiation was observed by paraffin sections. The contents of abscisic acid (ABA), indole-3-acetic acid (IAA), gibberellin (GA3) and zeatin nucleoside (ZR) in leaves in different flower development periods and in leaves with flower bud and leaves without flower bud in annual growth cycle were determined by enzyme-linked immunosorbent assay (ELISA). The results were as follows: (1) The flower bud differentiation sequence of C. perpetua was from the outside to the inside, and it was divided into six periods, which lasted 35 d in total, from the bud differentiation to flowering about two months. (2) The contents of ABA and GA3 and the ratios of GA3/ABA and (IAA + GA3) /ZR were higher in flower bud morphological differentiation period, while the contents of IAA and ZR and the ratios of IAA/ABA and ZR/ABA were lower. (3) The contents of ABA, IAA and ZR in the leaves with flower bud were higher than those in the leaves without flower bud. The IAA/ZR and (IAA + GA3) /ZR ratios were lower than those of the leaves without flower bud. In conclusion, the flower bud differentiation to flowering time of C. perpetua is shorter. High levels of ABA and GA3 and low levels of IAA and ZR are beneficial to flower bud differentiation; higher levels of ABA, IAA and ZR are beneficial to flower bud development. The study provides the reference for clarifying the continuous flowering mechanism of this species.