Alteration of Flower Yield and Phytochemical Compounds of Saffron (Crocus sativus L.) by Application of Different Light Qualities and Growth Regulators

Saffron is the world's most coveted spicy plant that has medicinal value. Currently, due to diverse types of difficulties in growing this plant outdoor, the tendency to produce it indoor has been increased. Optimized indoor conditions for growing saffron plants is not fully determined so far. This study was conducted to investigate the interactive effects of two plant growth regulators (PGRs), including gibberellic acid (GA(3)) and gamma-aminobutyric acid (GABA) and four light recipes, including white, monochromatic blue, monochromatic red, and a combination of 50% red and 50% blue on the flower yield and phytochemical components (such as crocin, picrocrocin and safranal) in stigmas of indoor-grown saffron. The results showed that exogenous GABA application and combined red and blue LED lights enhanced the performance of saffron flowers in terms of the number of flowers (up to 1.97 per corm) as well as the fresh and dry weight of flowers and stigmas. In saffron, the concentration of three major secondary metabolites is of great importance since it determines its commercial, pharmaceutical quality. GABA induced saffron's chemical ingredients toward the phytochemicals safranal (up to 5.03%) and picrocrocin (up to 15.8%), while GA(3) induced them toward the carotenoid pigment crocin (up to 25.1%). In conclusion, the application of GABA with a combination of red and blue lights enhanced the production of high-quality stigmas and positively affected the yield of flowers in saffron plants.