Lina Zhao

Understanding the mechanisms that regulate the timing of flower opening remains limited. Here, we use the heterodichogamous species Ziziphus jujuba, which contains Early and Late morphs, as a model to investigate these mechanisms. We examined the effects of different light/dark regimes on flower opening, alongside analyses of hormones during floral development, combined with exogenous hormone treatments and transcriptome profiling. Our results show that flower opening in both morphs was synchronized regardless of diel, inverted, or continuous light conditions, indicating circadian control. IAA and ABA accumulated during and after opening, respectively. Exogenous auxin treatment promoted earlier flower opening, whereas inhibition of auxin signaling reduced flower opening. Transcriptome analysis revealed the circadian clock and hormone-related pathways underlying these processes, further supporting the interaction between endogenous rhythms and hormonal signalling in regulating the timing of flower opening. Together, these findings demonstrate that the timing of flower opening in Z. jujuba is regulated by circadian rhythms and hormonal signaling. This study provides a framework for better understanding the regulatory mechanisms controlling the timing of flower opening in heterodichogamous and potentially other species.