Effect of light spectrum on growth, development, and mineral contents of okra (Abelmoschus esculentus L.)

Influence of the light spectrum on growth, development, and nutrients contents of okra was studied by growing okra (Abelmoschus esculentus L.) under three different LED-based irradiations defined by their peak wavelength at 455.45 +/- 1.80 nm (B-455), 522.27 +/- 1.46 nm (G(522)), and 635.03 +/- 1.33 nm (R-635), respectively in the blue, green, and red regions of the visible spectrum. The photosynthetic photon flux density (PPFD) of 200 mu mol m(-2) s(-1) was provided by the LEDs for 18 h daily. Leaves macronutrients and micronutrients concentration and plant biometric parameters were measured 60 days after sowing; the evolution of biometric parameters was also monitored during the growing period. Results related to biometric parameters have shown that highest leaf area, plant height, and fresh and dry weight were achieved under B-455 light; both R-635 and G(522) lights produce the highest quantity of leaves; and largest stem diameters were observed under B-455 and G(522) lights. Regarding mineral contents, highest calcium, phosphorus, and manganese concentrations were obtained under R-635 light; highest sodium content was observed under G(522) light; and the highest nitrogen content was obtained under both B-455 and G(522) lights. However, there were no significant differences observed for potassium, magnesium, and zinc concentrations among the three light treatments. These results revealed that selective spectrum in artificial lighting design can be strategically used to optimize the plant growth, development, and mineral contents uptake under controlled environments.