Abstract
Light plays a crucial role in several physiological processes in plants, ranging from photosynthesis to the biosynthesis of secondary metabolites such as carotenoids. The emergence of Light-Emitting Diode (LED) technology, has granted researchers unprecedented control over light quality and intensity, enabling detailed research into its effects on plant growth, development, flowering, and secondary metabolite accumulation, such as carotenoids. Carotenoids, vital pigments in plant physiology, serve for pollinator attraction, photoprotective molecules, and precursors for vitamin A biosynthesis. Carrots (Daucus carota) known for their high carotenoid levels provide an excellent model for studying the impact of light on carotenoid biosynthesis and taproot development. In a comprehensive study exploring the effects of different light conditions on carrot storage root development and carotenoid content, we employed three lighting regimes: fluorescent light (F) with a high green light content, LED light with a spectrum enriched in blue and red wavelengths (NS12), and LED light with a higher content in Red and Far-Red light and with the highest light intensity (AP67). Our findings revealed that NS12 and AP67 induce an early development of secondary root growth due to carrot storage roots exhibiting wider and heavier storage roots compared to those grown under F light. Together, these findings correlate with an enhancement in carbon fixation, as evidenced by the improved levels of sucrose and starch under LED lighting. Despite these differences, there were no observable variations in carotenoid content. However, there was an induction of DcPSY1 and DcPSY2 expression in 8 weeks old storage roots of plants grown under LED lights. Taken together, the quality and intensity of aboveground light in which the carrot is grown significantly affects the development of the storage root but not on carotenoid content. These findings underscore the profound influence of light quality on underground organs and highlight the potential of LED technology to optimize crop production by promoting favourable traits in storage organs.