Iron biofortification of broccoli microgreens under different radiation spectrum and composition of nutrient solution

In this study, broccoli microgreens 'Green' were grown indoors (T 21/17 degrees C; RH 55%) for ten days under red 660 nm and blue 447 nm light-emitting diodes (LEDs) at 9:1 and 1:3 ratios (PPFD 200 mu mol m(-2) s(-1)) and in nutrient solution containing 2, 5, and 15 ppm of Fe. The highest content of Fe was found in broccoli treated with 1:3x15 ppm. Interestingly, broccoli treated with 9:1x15 ppm, and 1:3x5 ppm accumulated the same amount of Fe. Also, the highest translocation factor was calculated from leaves and roots of broccoli treated with 1:3x15 ppm. The bioaccumulation factor decreased with increasing concentration of Fe in nutrient solution regardless of the radiation spectrum. Broccoli microgreens formed significantly larger leaves under 9:1x2 ppm, and longer hypocotyls under 9:1x15 ppm. The chlorophyll, flavonol, and nitrogen balance, and plant senescence reflectance indexes were the highest of plants under 1:3x15 ppm, 9:1x2 ppm, 9:1x15 ppm, 1:3x5 ppm, respectively. To sum up, the light can be used as a tool to increase the content of Fe in broccoli microgreens, but the uptake depends on the compositions of radiation spectrum and nutrient solution.