The impact of phytohormones on the number and quality of flowers in Crocus sativus

Abstract

Background: Phytohormones play pivotal roles in regulating floral development and secondary metabolite synthesis in saffron (Crocus sativus L.). Results: This study investigated the effects of gibberellin (GA), abscisic acid (ABA), cytokinin (CK), and strigolactone (SL) on floral differentiation, stigma quality, crocin yield, and endogenous hormonal dynamics. GA significantly accelerated floral bud differentiation and apical bud elongation during reproductive transition, increasing flower number by 23.5% compared to the control. While CK also enhanced flowering (17.6% increase), ABA and SL showed milder effects. Intriguingly, ABA treatment markedly elevated crocin content, boosting crocin 1 and 2 levels by 49.5% and 99.2%, respectively, and total crocin yield per corm by 1.7-fold-the highest among all treatments. Endogenous hormone levels were dynamically regulated, with GA and ABA treatments upregulating endogenous ABA. However, qRT–PCR analysis revealed downregulated expression of ABA biosynthesis genes (ZEP and NCED) under GA and ABA treatments. Conclusions: These findings highlight GA as the most effective hormone for increasing flower number and ABA as the optimal choice for enhancing crocin content. This study provides actionable insights for hormone-mediated agronomic strategies to simultaneously improve saffron’s ornamental and medicinal value.