Exogenous GA and IAA enhance germination of Cnidium monnieri via regulation of plant signalling-energy metabolism.

Abstract

The seed dormancy of Cnidium monnieri (L.) Cusson results in a low germination percentage. Gibberellins (GA) and Indole-3-acetic acid (IAA) are crucial phytohormones involved in breaking seed dormancy. However, the mechanism by which GA and IAA break dormancy in C. monnieri seeds remains unclear. We experimentally examined the effects of GA and IAA treatments on the seed germination of C. monnieri by verifying the associated changes in the levels of three phytohormones, key substances in the glycolytic pathway and the expressions of related genes. Our results showed that the treatments of GA (100 mg/L) and IAA (150 mg/L) significantly enhanced germination percentage. Following GA and IAA treatments, endogenous GA and IAA levels significantly increased with upregulation of their upstream and downstream genes (GA3ox, ARF, ALDH), whereas ABA levels significantly decreased and ABA signalling pathway genes (NCED, SnRK₂) were downregulated. Besides, GA and IAA treatments significantly promoted the glycolytic pathway, as demonstrated by the increased activities of key glycolytic enzymes (PFK and GAPDH), elevated levels of metabolic end-products (pyruvate and ATP) and upregulated expressions of encoding genes (PK, PFK). Our results demonstrate that GA and IAA treatments significantly promote GA and IAA signalling pathways while inhibiting the ABA signalling pathway, concurrently stimulating the glycolytic pathway to enhance carbohydrate catabolism and supply energy for increased germination. These findings elucidate that GA and IAA coordinate 'hormone signalling-energy metabolism' regulation in dormancy release of C. monnieri, establishing a critical technical framework for large-scale propagation and rapid activation of C. monnieri with ecological control function in field application.