Chemical modulation of ethylene responses alters floral organ identity, glandular trichome density, and cannabinoid accumulation in Cannabis sativa L. inflorescences

Cannabinoid accumulation in Cannabis sativa inflorescences is closely associated with floral organ identity and glandular trichome development, but the effects of chemically altered ethylene signaling on these traits remain unclear. We examined a dioecious Korean landrace to determine how silver thiosulfate (STS)-induced masculinization and ethephon-induced feminization affect floral development and cannabinoid accumulation. Floral morphology, surface structure, and anatomy were characterized using scanning electron microscopy and semi-thin sections, while cannabinoid synthase transcript levels, ethylene-signaling and floral-identity gene expression, and cannabinoid contents were evaluated using quantitative real-time PCR and high-performance liquid chromatography. STS-treated female inflorescences retained female-like inflorescence architecture but developed male-like floral structures with markedly lower glandular trichome density than untreated female flowers. These developmental changes coincided with reduced tetrahydrocannabinolic acid synthase and cannabidiolic acid synthase transcript abundance and an approximately 10% reduction in Δ⁹-tetrahydrocannabinolic acid content. By contrast, ethephon induced female-like flowers on male plants, accompanied by increased glandular trichome density and cannabinoid accumulation relative to male flowers. Total cannabinoid contents in leaves and leaf-derived calli did not differ substantially between male and female plants under the tested conditions. Male and female inflorescences also exhibited distinct developmental expression patterns of genes associated with ethylene signaling and floral identity, and STS treatment altered these patterns in female inflorescences. Collectively, these findings suggest that chemically induced changes in floral organ identity are associated with changes in cannabinoid accumulation together with altered tissue composition and glandular trichome abundance. This developmental framework may support sex-expression management and breeding strategies aimed at improving seed production and cannabinoid-yield consistency in industrial cannabis cultivation.