Endogenous phytohormone profiles in male and female floral buds of the persimmons (Diospyros kaki Thunb.) during development

Despite great interest from both the basic science community and from economic stakeholders, research on sex differentiation in persimmons (Diospyros kaki Thunb.) remains limited. Our previous study found that the developmental processes of both male and female floral buds were divided morphologically into 11 stages, of which stage 2 (on June 17) and stage 8 (on April 17 of the following year) were the two crucial morphological stages for sex differentiation. In this study, we used high-performance liquid chromatography-electrospray ionisation tandem mass spectrometry to measure the amounts of indole-3-acetic acid (IAA), gibberellin 3 (GA3), zeatin (ZT), abscisic acid (ABA), and jasmonic acid (JA) in both male and female floral buds at stages 1, 1.5, 2, 6, 7, 8, 10, and 11 to uncover the regulatory effects of endogenous phytohormones on sex differentiation. The results showed that low levels of IAA, ABA, as well as the ratio of ABA to IAA, and high levels of GA3 in male floral buds in the middle of June were related to the formation of three-flower cymes. Moreover, high levels of GA3 in male floral buds at stage 8 may accelerate the arrest of pistil primordia and the development of stamen primordia in the middle of the following April. In addition, high levels of the ratio of ABA to ZT from stages 6–11 might promote the differentiation of male floral buds. However, high levels of IAA from stages 7–10 as well as ZT and ABA from stages 6–10 in female floral buds may stimulate the abortion of stamen primordia and promote the development of pistil primordia, leading to female unisexual flowers. These results are relevant for future research on the regulation of controlled sex differentiation and pollination with exogenous phytohormones.