Integrated light spectrum and growth regulators improved the growth of saffron daughter corms by regulating carbohydrate metabolism in a novel two-stage cropping system.

BACKGROUND: Saffron, a valuable spice and industrial crop used in food, pharma, and cosmetics, is propagated only vegetatively via corms due to triploid male sterility. Corms are the primary storage organs and determine both the yield and quality of daughter corms. However, the optimal growing conditions for producing large, heavy daughter corms remain unclear. MATERIALS AND METHODS: Here, we examined the effects of light spectra and plant growth regulators on photosynthetic pigments, starch accumulation, and daughter corm production in a two-stage system, with reproductive growth occurring indoors followed by outdoor maturation. The plants were grown under four light spectra: white, red, blue, and a combination of half red and half blue. Two plant growth regulators, gibberellic acid and gamma-aminobutyric acid, were applied during the reproductive stage of the plant. After flowering, the mother corms were directly transplanted to the field for the development of daughter corms. RESULTS: The combination of red and blue light with gamma-aminobutyric acid produced the heaviest daughter corms, reaching 8.7 g dry weight, and the highest starch accumulation in the corms reached 383 milligrams per gram fresh weight. Red and blue light combined with gibberellic acid increased the leaf starch concentration to 926 milligrams per gram of fresh weight. A higher pigment content and larger leaf area support greater photosynthetic performance, preserve carbohydrate reserves in mother corms, and ultimately favor the production of heavier daughter corms. CONCLUSIONS: These results provide practical insights for optimizing saffron propagation in controlled-environment and field systems, directly contributing to industrial-scale production and value chain efficiency. Future research should test dynamic light spectra and optimized regulatory strategies to refine corm development and strengthen commercial and industrial saffron production.