The mechanism underlying seed germination promotion by plant growth-promoting rhizobacteria (PGPR) remains unclear. This study investigated the effects of Bacillus subtilis QM3 (a PGPR) and gibberellic acid (GA₃) on germination indexes, seedling growth, and amylase activity in wheat seeds (Triticum aestivum L.) (caryopses) at different germination times. The results showed that B. subtilis QM3 exhibited a significantly greater increase in most measured indicators compared to GA₃ (p < 0.05), and the coordinated effect of bacteria QM3 and GA₃ was superior. GA₃ showed no promotion of radicle length (LR) from day 3 to day 7. Conversely, the addition of uniconazole (U), a gibberellin synthesis inhibitor, significantly reduced all indexes except for fresh weight (FW) and root-shoot ratio (RSR). However, both B. subtilis QM3 and GA₃ significantly alleviated the inhibition (p < 0.05), especially in the germination rate and amylase activity. The gibberellin (GA) content and expression of two key biosynthetic enzyme genes were also characterized. Further investigations revealed that the GA content in the B. subtilis QM3 group was significantly higher than in the control group at 12 h, 24 h, and 48 h during seed germination (p < 0.05). Moreover, B. subtilis QM3 significantly increased TaGA3ox-B2 expression (p < 0.05), with 1.44 times that of the control group, while there was no significant effect on TaGA20ox-D2 expression. Furthermore, amylase activity was positively correlated with the germination rate (GR) and GA content was positively correlated with amylase activity according to Pearson’s correlation analysis, with R² values of 0.8102 and 0.8365, respectively. Our results demonstrate that one of the mechanisms by which B. subtilis QM3 promotes wheat seed germination may be the induction of GA biosynthesis.

植物根际促生长细菌（PGPR）促进种子发芽的机制仍不清楚。本研究探讨了枯草芽孢杆菌QM3（a PGPR）和赤霉酸（GA ₃ ）对不同发芽时间小麦种子（ Triticum aestivum L.）（颖果）发芽指数、幼苗生长和淀粉酶活性的影响。结果表明，枯草芽孢杆菌QM3与GA ₃相比，大多数测定指标均表现出显着更大的增加（p < 0.05），并且细菌QM3和GA ₃ 的协同效果更优越。 GA ₃从第 3 天到第 7 天没有显示出胚根长度（LR）的增加。相反，添加赤霉素合成抑制剂烯效唑（U）显着降低了除鲜重（FW）和根冠比之外的所有指标（ RSR）。然而，枯草芽孢杆菌QM3 和 GA ₃均显着减轻了抑制作用（p  < 0.05），特别是在发芽率和淀粉酶活性方面。还对赤霉素 (GA) 含量和两个关键生物合成酶基因的表达进行了表征。进一步研究发现，在种子萌发过程中12 h、24 h、48 h时，枯草芽孢杆菌QM3组的GA含量显着高于对照组（p  < 0.05）。此外，枯草芽孢杆菌QM3显着增加TaGA3ox-B2表达（p <0.05），是对照组的1.44倍，而对TaGA20ox-D2表达 没有显着影响。此外，根据Pearson相关分析，淀粉酶活性与发芽率（GR）呈正相关，GA含量与淀粉酶活性呈正相关，R ²值分别为0.8102和0.8365。我们的结果表明，枯草芽孢杆菌QM3 促进小麦种子萌发的机制之一可能是诱导 GA 生物合成。