Anything New under the Sun? An Update on Modulation of Bioactive Compounds by Different Wavelengths in Agricultural Plants

Abstract

Plants continuously rely on light as an energy source and as the driver of many processes in their lifetimes. The ability to perceive different light radiations involves several photoreceptors, which in turn activate complex signalling cascades that ultimately lead to a rearrangement in plant metabolism as an adaptation strategy towards specific light conditions. This review, after a brief summary of the structure and mode of action of the different photoreceptors, introduces the main classes of secondary metabolites and specifically focuses on the influence played by the different wavelengths on the content of these compounds in agricultural plants, because of their recognised roles as nutraceuticals.

Supplemental UV-B Exposure Influences the Biomass and the Content of Bioactive Compounds in Linum usitatissimum L. Sprouts and Microgreens

“…No previous studies have reported the influence of UV-B exposure on such health-promoting compounds specifically in flaxseed sprouts or microgreens. However, many manuscripts have investigated UV-B-induced effects in several crops, mostly agreeing on the general positive impact of UV-B irradiation on the total phenolic content [16]. In accordance with our results, a pre-harvest UV-B supplementation increased the total phenolic and flavonoid concentration in basil [70,71] and lettuce [72].…”

“…Conversely, flavonoids were more concentrated in microgreens than in sprouts, which might be due to the older developmental stage and consequently the longer light exposure prior to harvesting. Indeed, it is well known that flavonoid biosynthesis and accumulation are strongly influenced by light exposure, both in terms of quality and quantity [16,44,45]. The influence of light in phenolic biosynthesis and accumulation is well visible when comparing our results with those obtained by Puccinelli et al [28].…”

“…To avoid the potential damage to macromolecules and the photosynthetic apparatus caused by highly energetic UV-B radiation and UV-B-induced reactive oxygen species (ROS), plants have evolved a dedicated intracellular pathway [9,10], leading to the biosynthesis and accumulation of protective metabolites, such as phenolic compounds [11][12][13]. UV-B exposure was also found to impact other classes of phytochemicals, e.g., carotenoids, alkaloids, glucosinolates, and several vitamins [14][15][16][17][18][19]. UV-B irradiation, as an eco-friendly tool to enhance the nutraceutical quality of crops when applied in pre-and post-harvest, has gained great interest among researchers [20,21].…”

Can Light Spectrum Composition Increase Growth and Nutritional Quality of Linum usitatissimum L. Sprouts and Microgreens?

“…Recent studies have highlighted the possibility of regulating seedling growth and increasing the content of pivotal nutritional compounds and secondary metabolites through appropriate regulation of the light spectrum used during germination. Many recent studies underlined the diversity of response of several crops towards different light conditions, in terms of both quality (wavelength) and dose (intensity and duration of exposure) [20,21]. Particularly, recent studies on microgreens and sprouts have shown the strong influence of red-and blue-light supplementation on carotenoids, chlorophylls, and phenolics accumulation in several plants of food interest, e.g., soybean, mustard, beet, pak choi, and parsley [22][23][24].…”

UV and Visible Spectrum LED Lighting as Abiotic Elicitors of Bioactive Compounds in Sprouts, Microgreens, and Baby Leaves—A Comprehensive Review including Their Mode of Action

“…Therefore, physical elicitation produced by the light perceived can be controlled to trigger the activation of the plant secondary metabolism as a defence mechanism against light incidence through the use of LEDs, also stimulated by photoreceptors and genes that are activated against abiotic stresses [7].…”