Ethylene sensitivity assay for medicinal and fiber-type Cannabis seedlings reveals a triple-response-like phenotype

As evidence mounts for ethylenes important role in sex determination, understanding ethylene signaling in Cannabis sativa L. (cannabis) has become increasingly vital. This study investigated the response of hemp-type and drug-type Cannabis sativa seedlings to ethylene, revealing a unique paired response phenotype under dark conditions and ethephon treatment, suggesting a more specialized variation of the triple response distinct from that observed in other species. Employing a novel ethephon-based assay, this research bypassed the complexities of using gaseous ethylene, providing a more accessible method for examining ethylene responses. The results showed C. sativa seedlings exhibit marked sensitivity to ethephon at concentrations (125 mg/L, 250 mg/L, and 500 mg/L) lower than those previously reported to influence mature plants, indicating a broad ethylene responsiveness across various genetic backgrounds. Furthermore, the reversal of ethylene-induced phenotypic changes by silver thiosulfate (STS) at all concentrations tested (1, 2, and 3 mM) suggests the conservation of ethylene signaling pathways in C. sativa. Importantly these phenotypic responses were observed in both drug and hemp type cannabis. However, the absence of an exaggerated apical hook in treated seedlings potentially points to a unique regulatory mechanism in response to ethylene in achene-bearing plants. These findings, highlighted by the successful induction of ethylene-sensitive phenotypes, underscore the conserved nature of ethylene signaling in C. sativa. The results highlight the need for further investigations into the regulatory mechanisms of ethylene in cannabis, especially concerning sexual development, opening new pathways for optimized breeding and cultivation practices aimed at enhancing plant growth and reproductive strategies.