Changes in Endogenous Hormone Contents during Seed Germination of Anemone rivularis var. flore-minore

Abstract The regulation of endogenous hormones in seed germination and dormancy has been discussed widely in Arabidopsis and crops species, but wild species are rarely examined. In this study, seeds of Anemone rivularis var. flore-minore, a common species in the alpine meadows, were used to test the relationships between endogenous hormone levels and seed germination. The contents of abscisic acid (ABA), gibberellic acid (GA), trans-zeatin (ZT) and indole-3-acetic acid (IAA) in dry, imbibed, and germinated seeds that incubated in either light (12 h/12 h light/dark) or dark (24 h dark) periods were detected by reversed phase high-performance liquid chromatography (RP-HPLC) with ultraviolet detection. When seeds cultivated in the light were compared to those in the dark, A. rivularis seeds germinated more efficiently and had significantly higher values of ZT content and ZT/ABA ratio in light. Meanwhile, the values of ZT/GA, ZT/IAA, and GA/ABA showed increasing trends while ABA content decreased. The effects of light on hormone contents were great in the early stages of seed imbibition and were significantly weakened during late imbibition. The half imbibition time point (the ninth day) revealed to be a turning point of variation within endogenous hormone contents of A. rivularis, especially with ABA content. The half imbibition time point also resulted in the lowest value ZT/ABA, GA/ABA and IAA/ABA. After that point, ZT remained high, IAA levels remained low, and GA and ABA decreased from their respective peaks. As the imbibition process moved forward, IAA content decreased and the common trend of GA and ABA increasing then decreasing was also observed. Transitioning to later imbibition time points of seed gemination (the 17th d), whether light was considered or not, the values of GA, IAA, and ABA contents remained at a lower hormone level, except for ZT. At the same time, ZT/ABA, GA/IAA and ZT/IAA showed the highest values during germination. When assessing pair-wise hormone correlations, the imbibition time strengthened the GA-IAA positive correlation but weakened the GA-ABA positive correlation found when imbibition time was not controlled. Furthermore, by controlling for the light conditions, the ZT-IAA and ZT-ABA correlations were strengthened. These results suggest that both light condition and seed imbibition time play roles during seed germination of A. rivularis by regulating hormone levels and their interactions to some extent.