Exogenous GA3 Promotes Germination by Reducing Endogenous Inhibitors in Sainfoin (Onobrychis viciifolia) Seeds

Endogenous inhibitors can inhibit seed germination, and GA₃ can promote seed germination. Whether GA₃ can affect the changes in endogenous inhibitors has not been clarified. In order to study the effect of GA₃ on the endogenous inhibitors in sainfoin (<i>Onobrychis viciifolia</i>) seeds, the systematic separation method and gas chromatography-mass pectrometry (GC-MS) method were used to determine the endogenous inhibitors using cabbage (<i>Brassica rapa</i> var. glabra Regel) as a bioassay model to validate the inhibitory activity in sainfoin seeds, and then the optimal concentration of GA₃ was determined to promote seed germination. The results showed that endogenous inhibitors existed in the pod coat, seed coat, and seed embryo of sainfoin seeds, with the methanol and ethyl acetate phases showing the highest degree of inhibition. The organic compounds were mainly organic acids, phenols, lipids, and alkanes. The levels of changes in germination indicators, storage substances, and antioxidant enzymes determined that 600 mg/L GA₃ was the optimum concentration to promote germination of sainfoin seed. It was also found that 600 mg/L GA₃ reduced the relative content of endogenous inhibitors and changed the content of endogenous hormones. In summary, the presence of endogenous inhibitors may be one of the reasons for the low germination rate of sainfoin seeds, with 3-methoxycatechol and 4-nitrosodiphenylamine playing a major role. GA₃ can reduce the relative content and types of endogenous inhibitors to promote the germination of sainfoin seeds. Our experimental results provide the basis for subsequent exploration of the mechanism of specific endogenous inhibitors and the identification of deeper molecular mechanisms.