Blue and red LEDs application in horticultural lighting for mineral absorption of okra leaves at the late growth stage

Fruit vegetables, including okra (Abelmoschus esculentus L.), are considered healthy due to their high content of fiber, folate, carotenoids, phenolic and antioxidant compounds, minerals, and vitamins A, C, and K. Light is a key abiotic factor in the regulation of plant physiology and development, influencing a multitude of processes via specialized photoreceptors. By reproducing or adjusting natural light conditions—largely due to technological advances in light-emitting diodes (LEDs)—horticultural lighting can precisely modulate plant development in a controlled environment, thus opening new perspectives in precision agriculture. As macronutrients and micronutrients are essential and beneficial for both plant and human health, the objective of this study is to evaluate the mineral concentration of okra plant leaves subjected to three types of LED lighting: blue (445 nm), red (660 nm), and the alternation of blue and red every 3 days. To do this, okra leaf samples grown under these three light treatments underwent physical treatment, and their mineral contents were determined by X-ray fluorescence spectroscopy. To discriminate between these different light treatments, the data obtained were statistically evaluated using ANOVA and PERMANOVA methods. Sulfur (S) and manganese (Mn) concentrations were significantly higher under blue light compared with the other treatments. The alternating blue/red regime produced the lowest strontium (Sr), S, and Mn levels, which did not differ significantly from those observed under red light. Red light induced the highest phosphorus (P) concentration. These results open the way to foliar quality engineering strategies based on dimmable LED lighting systems.