The Variations of C/N/P Stoichiometry, Endogenous Hormones, and Non-Structural Carbohydrate Contents in Micheliamaudiae 'Rubicunda' Flower at Five Development Stages

Michelia maudiae 'Rubicunda' (M. maudiae 'Rubicunda') is one of the most popular ornamental plants. However, relatively little is known regarding its floral development. Here, the variations of the mineral, endogenous hormone, and non-structural carbohydrate (NSC) contents in the petals and gynoecium and androecium (GA) at five developmental stages during M. maudiae 'Rubicunda' flower development were analyzed. The results suggested that the carbon (C), nitrogen (N), and phosphorus (P) endogenous hormones, NSC contents, and C/N/P stoichiometric ratios exhibit large variations during flower development. There were significant differences in N and P contents in the GA and petals among the five growth stages, while C contents did not change significantly. In the five flower development stages, the average N and P contents in the GA were higher than those in the petals. The maximum C/N and N/P ratios in the GA and petals were foundat the senescent flower stage (stage5) and green bud stage (stage1), respectively. The C/P ratio in petals reached its maximum value at the mature bud stage (stage 2), and the C/P ratio in the GA reached its maximum value at the senescent flower stage (stage 5). The C/N/P stoichiometric ratios in the petals were more sensitive to development stages than those in the GA. There were highly significant correlations between the NSC and C/N/P stoichiometric ratios in the GAand petals. Moreover, acetic acid (IAA), abscisic acid (ABA), gibberellic acid 3 (GA3), and cytokinin (CTK) contents in the petals exhibited significant changes in response to development stages. Principal component analysis (PCA) revealed significant correlations and clear differences in the test indexes between the development stage and organs, and the variation was explained by PC-1 (55.6%), PC-2 (23.3%), and the cumulative contribution percentage of the total biplot (78.9%). These studies can lay the foundation for elucidating the requirements and dynamic balance among C, N, P, NSC, and hormone contents during the flower development of M. maudiae' Rubicunda'.