Light-Quality Manipulation to Control Plant Growth and Photomorphogenesis in Greenhouse Horticulture: The State of the Art and the Opportunities of Modern LED Systems

Abstract

Light quantity (intensity and photoperiod) and quality (spectral composition) affect plant growth and physiology and interact with other environmental parameters and cultivation factors in determining the plant behaviour. More than providing the energy for photosynthesis, light also dictates specific signals which regulate plant development, shaping and metabolism, in the complex phenomenon of photomorphogenesis, driven by light colours. These are perceived even at very low intensity by five classes of specific photoreceptors, which have been characterized in their biochemical features and physiological roles. Knowledge about plant photomorphogenesis increased dramatically during the last years, also thanks the diffusion of light-emitting diodes (LEDs), which offer several advantages compared to the conventional light sources, such as the possibility to tailor the light spectrum and to regulate the light intensity, depending on the specific requirements of the different crops and development stages. This knowledge could be profitably applied in greenhouse horticulture to improve production schedules and crop yield and quality. This article presents a brief overview on the effects of light spectrum of artificial lighting on plant growth and photomorphogenesis in vegetable and ornamental crops, and on the state of the art of the research on LEDs in greenhouse horticulture. Particularly, we analysed these effects by approaching, when possible, each single-light waveband, as most of the review works available in the literature considers the influence of combined spectra.

Light Spectral Composition Influences Structural and Eco-Physiological Traits of Solanum lycopersicum L. cv. ‘Microtom’ in Response to High-LET Ionizing Radiation

“…Generally, the red (R) and blue (B) wavelengths are the most effective for photosynthesis and drive morphogenesis since the early developmental stages [ 4 ]. The B wavelength perceived through cryptochromes controls many processes such as stem elongation, phototropism, chloroplast movement within cells, stomatal opening, and elicits the biosynthesis of secondary metabolites such as flavonoids [ 5 , 6 ]. The R light contributes to photosynthetic apparatus development and influences morphogenesis.…”

Quality Evaluation of Indoor-Grown Microgreens Cultivated on Three Different Substrates

“…The growing medium plays a very important role in determining the microgreens' yield and quality [23], and the sustainability of the production process. Associated with this, in the last few years, an increased number of scientific papers reported the beneficial effects of LED light, in controlled environment agriculture, on plant growth and quality traits, including the accumulation of molecules of interest, such as carotenoids, phenolics, and glucosinolates [7,8,[30][31][32][33]. In the present work, different growing media usable for indoor microgreens cultivation were evaluated: vermiculite (inorganic material), coconut fiber (a natural, organic fiber), and jute (organic by-product and discarded material from several industrial processes).…”

Continuous Lighting Promotes Plant Growth, Light Conversion Efficiency, and Nutritional Quality of Eruca vesicaria (L.) Cav. in Controlled Environment With Minor Effects Due to Light Quality

“…Light is an essential environmental factor affecting plant growth, development, and phytochemical biosynthesis over short and long periods of growth as a result of the functionality exerted by radiation intensity and spectral composition. Plants exhibit high plasticity to variations in light characteristics either when using radiation as a source of energy for photosynthetic processes, or when it represents a signal to regulate photo-morphogenetic responses via a complex system of wavelength-specific photoreceptors (Paik and Huq, 2019;Paradiso and Proietti, 2021). The optimal light setting, in terms of light quantity and quality is a key element of controlled environment agriculture (CEA) where all factors are controlled to optimize productivity and resource use efficiency (Graamans et al, 2018).…”

“…However, the selection of optimal lighting conditions for the growth of different plant species is far from resolved. Extensive scientific literature highlights varying responses of plants to different light settings even when same light conditions are applied to different species (Paradiso and Proietti, 2021). Most of the studies conducted so far emphasize the role of red and blue wavelengths, when applied either individually or in a synergistic combination, due to the high absorption by photosynthetic pigments (Samuoliene et al, 2012;Wang et al, 2018).…”