Physiology and Transcriptome Analysis of Exogenous GA₃ Effects on the Seed Germination of Phyllostachys edulis

Phyllostachys edulis is a vital bamboo resource in China, known for its economic benefits and ecological functions. However, under natural conditions, its seed germination rate is very low. Exogenous gibberellin (GA) directly supplements endogenous GA levels, while paclobutrazol (PAC) is an inhibitor of GA biosynthesis that can prevent seed germination. Preliminary experiment indicated that a treatment of 50 mg/L GA₃ markedly enhanced the germination rate of P. edulis seeds, whereas 50 μmol/L PAC had an opposite function. To study the exogenous GA₃ effects on the seed germination of P. edulis, seeds were soaked in ddH₂O (CK), Gibberellic acid 3 (GA₃), and PAC solutions for 24 h, respectively. Then, we analyzed and compared the physiology, biochemistry, and transcriptome at different germination stages. The results demonstrated that exogenous GA₃ treatment significantly reduced the contents of starch and soluble protein while increasing the levels of soluble sugar by inducing the activities of β-amylase and protease, respectively. In addition, the activities of superoxide dismutase (SOD), polyphenol (PPO), and ascorbate peroxidase (APX) were enhanced to eliminate ROS during seed germination under exogenous GA₃ treatment compared to CK and PAC treatments. Moreover, the endogenous levels of GA₃ and JA were found to be higher in exogenous GA₃-treated seeds than those in CK and PAC-treated seeds. Furthermore, RNA-seq results revealed that the expressions of 10 related genes are consistent with the observed physiological changes. In summary, exogenous GA₃ effectively accelerated the seed germination of P. edulis by influencing storage reserves, antioxidant enzymes activity, and endogenous hormone through the coordinated transcriptional regulation of related genes. These findings provide novel insights into the regulation mechanisms of exogenous GA₃ on the seed germination of P. edulis.