Abstract

Light quality and intensity significantly affect the growth and development of horticultural crops. In carrot (Daucus carota L.), a species characterized by its high carotenoid content and edible storage root, we investigated how different light spectra impact underground organ development, carbohydrate accumulation, and carotenoid biosynthesis. Plants were grown under three lighting regimes: fluorescent light (F, enriched in green light), LEDNS12 (enriched in blue and red light), and LED-AP67 (rich in red and far-red light, with the highest intensity). Both LED conditions promoted earlier secondary root thickening, resulting in wider and heavier storage roots than those grown under fluorescent light, which correlate with the up regulation in the expression of DcPHYA, DcPHYB, DcPAR1 and DcARC6, that could be associated with secondary root development. This enhanced growth was also associated with increased sucrose and starch accumulation, suggesting improved carbon assimilation. While no significant changes in carotenoid content were detected, the expression of the key carotenoid biosynthetic genes DcPSY1 and DcPSY2 was upregulated under LED light. These results demonstrate that LED lighting can promote favourable agronomic traits in carrot storage roots, such as biomass and sugar accumulation, without compromising carotenoid stability. This study highlights the potential of LED technologies to optimize carrot production in controlled environments.