Impact of red-to-blue LED light ratios on the yield and phytochemistry of leafy green amaranths

Leafy green amaranth ( Amaranthus tricolor) is a crop of global importance due to its vigorous growth in resource-limited environments and rich nutritional content. Increased human migration to urban centers across the United States brings demands for culturally appropriate food items that meet the culinary preferences of incoming international communities. Leafy green amaranth is commonly eaten across South and East Asia, Sub-Saharan Africa, Latin America, and the Caribbean, and is therefore an important candidate for marketing to diverse urban populations interested in culturally relevant produce. Our study assessed the impact of different light spectra delivered to three accessions of baby amaranth greens grown in a hydroponic system installed in a growth chamber. The delivered light spectra had red:blue (R:B) ratios including 1:1.6, 1:1.1, 1.5:1, and 1.9:1. Plant yield traits assessed included shoot height, shoot fresh mass, number of leaves, and leaf area of 6-week-old baby greens, as well as nutritional traits including carotenoids, chlorophylls, betalain pigments, phenolic acids, and flavonoids. Our study found small differences in yield caused by the different R:B ratios, but significant differences in nutritional content. Results can be used to maximize the nutritional content of amaranth, without compromising leafy green yield.