Study on the physiological and biochemical characteristics of Brunfelsia acuminata petals during flowering

To explain the floral chromogenic mechanism of Brunfelsia acuminata Benth., 3-year-old B. acuminata petals during different flowering stages, including unfold-petal stage (UPS), initial-flowering stage (IFS), full-flowering stage (FFS), transitional-flowering stage (TFS), and flowering-wilting stage (FWS), were used and the floral color index, flavonoid content (FC), anthocyanin content (AC), carotenoid content (CC), pH index, relative enzyme activity and their correlations were measured. Results showed the flowering color change was not obvious during the UPS-IFS and TFS-FWS, the L value (bright parameter) increased gradually, whereas the A value (red/green parameter), B value (blue/yellow parameter), and C value (chroma) reduced sharply. The flavonoid content was lowest during the TFS, and there were no significant differences among the other stages. The carotenoid content trend was increasing-decreasing-stable, and the content during the FFS was the highest. The anthocyanin content decreased continuously from the UPS. The SOD activity from the UPS to FFS changed non-significantly but increased during the TFS and rapidly dropped to the lowest level during the FWS. The POD activity increased continuously and was highest during the FWS. The CAT activity changed non-significantly, and only increased in the late flowering stage. The correlations among the floral color index, anthocyanin content, POD activity, CAT activity, and pH value were significant, but were not significant among SOD activity, carotenoid content, flavonoid content, and other indexes. Anthocyanin was the decisive metabolite of B. acuminata flower color, and the activities of POD and CAT were the main antioxidant enzymes, which were involved in the adjustment of the anthocyanin degradation rate.