Effects of Light Emitting Diode High Intensity on Growth of Lettuce (Lactuca sativa L.) and Broccoli (Brassica oleracea L.) Seedlings

Abstract

Aims: To evaluate the effects of high intensity LED light with different wavelengths (red, blue, green and magenta filter) in physiology and absorption spectrum of lettuce (Lactuca sativa L.) and broccoli (Brassica oleracea L.) seedlings, with exposure times of 12 hours, in order to improve the growth of vegetables. Study Design: Four treatments of light (red, blue, green, magenta filter) and one control (white light). The experimental design was completely randomized, with two replications of 14 seedlings per experimental unit. Place and Duration of Study: The experiment was conducted at IPN - ESIME Zacatenco University, Mexico DF, between October 2013 and November 2013. Methodology: Seedlings were grown with alternating cycles of light (12hours) and darkness (12 hours). The period of growth of lettuce and broccoli was 29 and 15 days respectively. Physiological variables (fresh and dry weight, average length of hypocotyl, leaf number) and absorption spectrum of these vegetable seedlings were evaluated. Results: Seedlings of broccoli with green light and lettuce with red light exposed to high intensity LED light, showed statistically significant differences in average length of hypocotyl with increments of 33% and 42% compared to control respectively. The highest fresh and dry weight in broccoli seedlings was obtained in red light treatment with increases of 15% and 10% respectively, while in lettuce seedlings was 50 and 41% but with blue light compared to its control. Conclusion: The physiological responses produced by exposure to different wavelengths of high intensity LED light in broccoli and lettuce seedlings, varied according to the wavelength used, where the red LED light treatment had the best results in seedlings of broccoli, and lettuce seedlings was the blue LED light. Suggesting that the use of high intensity LED light is a viable option to improve plant growth in controlled environments.