Abstract
Plant antioxidants are important compounds involved in plant defense, signaling, growth, and development. The quantity and quality of such compounds is genetically driven; nonetheless, light is one of the factors that strongly influence their synthesis and accumulation in plant tissues. Indeed, light quality affects the fitness of the plant, modulating its antioxidative profile, a key element to counteract the biotic and abiotic stresses. With this regard, light-emitting diodes (LEDs) are emerging as a powerful technology which allows the selection of specific wavelengths and intensities, and therefore the targeted accumulation of plant antioxidant compounds. Despite the unique advantages of such technology, LED application in the horticultural field is still at its early days and several aspects still need to be investigated. This review focused on the most recent outcomes of LED application to modulate the antioxidant compounds of plants, with particular regard to vitamin C, phenols, chlorophyll, carotenoids, and glucosinolates. Additionally, future challenges and opportunities in the use of LED technology in the growth and postharvest storage of fruits and vegetables were also addressed to give a comprehensive overview of the future applications and trends of research.
Highlights
Plant antioxidants include a wide variety of compounds, which are responsible for essential plant functions, including signaling, defense, oxidative damage prevention, and free-radical scavenging [1]
Despite the majority of the studies being only focused on the measurement of the total phenol content (TPC), total flavonoid content (TFC), or of specific phenolic compounds, few of them reported that these increments after white light (WL), blue light (BL), and RL treatments were due to the increased activity of the key enzymes of the shikimate and phenylpropanoid pathways, such as phenylalanine ammonia lyase (PAL) [101,102], chalcone synthase (CHS), chalcone isomerase (CHI), or in flavonoid and anthocyanin synthesis pathways, such as flavonol synthase (FLS), leucoanthocyanidin dioxygenase (LDOX), dihydroflavonol
Most of the results showed that BL promotes the accumulation of phytochemical constituents, including polyphenol in bananas (Musa acuminate) [100], Vit C in citrus juices (Citrus unshiu and Citrus sinensis) [72], Chinese cabbage (Brassica campestris) [75], and strawberry (Fragaria ananassa) [75], and anthocyanin in sweet cherries (Prunus avium) [84] and in Chinese bayberry fruit (Myrica rubra) [185]
Summary
Plant antioxidants include a wide variety of compounds, which are responsible for essential plant functions, including signaling, defense, oxidative damage prevention, and free-radical scavenging [1]. According to the receptor type, they can be sensitive to both low and high irradiance levels, as well as to specific light wavelengths [18] Due to such implications, artificial light supplementation has been widely applied in horticulture on economically relevant crops to compensate for short photoperiods, to support photosynthesis, to control plant flowering and pests, and to improve plant nutritional quality [19]. LEDs show unique spectra outputs in terms of wavelengths, along with an equivalent luminous efficacy, lower operational cost, lack of radiant heat, and longer lifespan Due to these unique advantages, LEDs are used in controlled environments, e.g., growth chambers, greenhouses, and vertical farming, as well as in the postharvest storage of many vegetables to support plant growth and to stimulate the synthesis of bioactive compounds [21]. An overview of the most recent findings in the horticultural field is provided, and the challenges and perspectives of LEDs application at all levels of the supply chain are critically discussed
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