COLORED LED REDUCES ENERGY USE, AFFECTING LETTUCE SEED GERMINATION, GROWTH, AND ANTIOXIDANT ACTIVITY POSITIVELY

As vegetables have been growing and space has gathered on the market, there is increasing demand for alternative light sources. This research aimed to analyze the possible changes in lettuce (Lactuca sativa) seed germination and initial seedling growth under different light spectra. Seeds were germinated in a chamber at 20°C under a 12-hour photoperiod. The light treatment in the first phase consisted of white and colored light-emitting diode (LED) lights (red-V + blue-A) in proportions of 100% V, 80% V + 20% A, 50% V + 50% A, and 80% A + 20% V. The first phase of the experiment consisted of a completely randomized design in a 2x4 factorial scheme (two light conditions and four seed lots) with four replications. The first count, germination, germination speed index (GSI), root length, shoot length, total seedling length, and shoot-to-root ratio were evaluated via image analysis. For the second phase of the experiment, the quantification of antioxidative enzyme activity (SOD, CAT, and APX) was performed to assess whether the light treatments (white LED light, colored LED light, and fluorescent light) caused photooxidative damage in the seedlings. Compared with white LED light, colored LED light improved plant germination and growth by promoting faster radicle protrusion, a greater GSI, a longer total seedling length, and a longer primary root length. The quantification of SOD, CAT, and APX activity indicated that the quality of light used in this work did not cause photooxidative stress in lettuce plants.