Impact of varying light spectra on the biochemical and physiological parameters of lettuce (Lactuca sativa L.)

Abstract

The search for plants that can increasingly adapt to diverse environmental conditions has intensified in recent years. In order to understand the biochemical and physiological responses of lettuce (Lactuca sativa L.) to light, plants of this species were grown under monochromatic LEDs emitting blue, warm white, blue + red, and red light, as well as under a comparative condition of natural light. The experiment was conducted in a randomized block design, with five lighting treatments, four cultivationcycles as blocks, and six plants per experimental unit. The production of total soluble sugars, chlorophyll a, chlorophyll b, total chlorophylls, carotenoids, photosystem II quantum efficiency, and the SPAD index was analyzed. Among the biochemical analyses conducted, sugar production was reduced only in plants exposed to warm white LEDs. Regarding chlorophyll a, total chlorophylls, and carotenoids, monochromatic blue and blue + red LEDs stood out, whereas chlorophyll b production did not differamong treatments under the environmental conditions of this experiment. Based on physiological analyses, photosystem II quantum efficiency was higher in plants irradiated with blue and natural light, while the SPAD index was highest under blue + red, blue, and natural light. Blue and blue + red spectra promoted superior photosynthetic performance and pigment accumulation, indicating that these wavelengths are more suitable for optimizing physiological quality of lettuce grown under controlled environments.