Stage-specific regulation of soybean stem growth by exogenous gibberellin (GA₃)

Gibberellin (GAs) plays a key role in soybean stem elongation, with its effects being highly dependent on the developmental stage. In this study, exogenous GA₃ was applied to soybean stems at the V1 and V4 growth stages to investigate changes in cell wall components and their associated gene expression. The results demonstrated that GA₃ promoted plant height and internode elongation while reducing the contents of lignin, cellulose, and hemicellulose, with more pronounced effects observed at the V1 stage. Transcriptome analysis revealed that GA₃ treatment at V1 induced a greater number of differentially expressed genes (DEGs), which were significantly enriched in pathways including diterpenoid biosynthesis, plant hormone signal transduction, phenylpropanoid biosynthesis, and cutin, suberine, and wax biosynthesis. Key genes, such as PAL and CCoAOMT, were markedly upregulated. In summary, the response of soybean stems to GA₃ exhibits clear stage specificity, with a strong growth-promoting effect at the V1 stage and a weaker response at the V4 stage. This study elucidates the stage-specific regulatory network of soybean stems in response to GA₃ and provides a theoretical basis for improving plant architecture and lodging resistance in crops.