Unraveling the Role of Red:Blue LED Lights on Resource Use Efficiency and Nutritional Properties of Indoor Grown Sweet Basil

Abstract

Indoor plant cultivation can result in significantly improved resource use efficiency (surface, water, and nutrients) as compared to traditional growing systems, but illumination costs are still high. LEDs (light emitting diodes) are gaining attention for indoor cultivation because of their ability to provide light of different spectra. In the light spectrum, red and blue regions are often considered the major plants’ energy sources for photosynthetic CO2 assimilation. This study aims at identifying the role played by red:blue (R:B) ratio on the resource use efficiency of indoor basil cultivation, linking the physiological response to light to changes in yield and nutritional properties. Basil plants were cultivated in growth chambers under five LED light regimens characterized by different R:B ratios ranging from 0.5 to 4 (respectively, RB0.5, RB1, RB2, RB3, and RB4), using fluorescent lamps as control (CK1). A photosynthetic photon flux density of 215 μmol m−2 s−1 was provided for 16 h per day. The greatest biomass production was associated with LED lighting as compared with fluorescent lamp. Despite a reduction in both stomatal conductance and PSII quantum efficiency, adoption of RB3 resulted in higher yield and chlorophyll content, leading to improved use efficiency for water and energy. Antioxidant activity followed a spectral-response function, with optimum associated with RB3. A low RB ratio (0.5) reduced the relative content of several volatiles, as compared to CK1 and RB ≥ 2. Moreover, mineral leaf concentration (g g−1 DW) and total content in plant (g plant−1) were influences by light quality, resulting in greater N, P, K, Ca, Mg, and Fe accumulation in plants cultivated with RB3. Contrarily, nutrient use efficiency was increased in RB ≤ 1. From this study it can be concluded that a RB ratio of 3 provides optimal growing conditions for indoor cultivation of basil, fostering improved performances in terms of growth, physiological and metabolic functions, and resources use efficiency.

Photosynthesis, Morphology, Yield, and Phytochemical Accumulation in Basil Plants Influenced by Substituting Green Light for Partial Red and/or Blue Light

“…Consistently, Zhang and Folta (2012) reported that as green light intensity increased, the amount of anthocyanin in arabidopsis decreased to half the level present in plants grown under combined R&B light. Also, Pennisi et al (2019) reported that substituting green light for red light significantly decreased antioxidant capacity and flavonoid concentration in basil plants. It was postulated that the decreased phytochemical concentration under green light treatments is caused by the coactions of decreased red and/or blue light proportions and an increasing reversal of blue light-induced effects by green light.…”

The Growth and Development of Sweet Basil (Ocimum basilicum) and Bush Basil (Ocimum minimum) Grown under Three Light Regimes in a Controlled Environment

“…A recent study sought to un-pick the influences of Red and Blue light on growth and photosynthetic efficiency in sweet basil and found that quantum efficiency in PSII was lower under Red/Blue LED light arrays when the Red portion of the light array was greater than double the Blue (2:1). This was reversed when light ratios were more equal (1:1) [57]. It is the presence of the Photosystem II Primary Donor protein P680 in PSII which absorbs maximum light energy at 680 nm (Red) and Photosystem I Primary Donor P700 in PSI which absorbs maximum light energy at 700 nm (Red) and these might be responsible for the effects on the stomatal conductance Gs [58][59][60].…”

Impacts of LED spectral quality on leafy vegetables: Productivity closely linked to photosynthetic performance or associated with leaf traits?

“…In the indoor plant cultivation of sweet basil (Ocimum basilicum cv. Superbo, Sais seeds, Cesena, Italy), Pennisi et al (2019) also reported that the greatest biomass production was achieved with the correct combination of RB-LED lightings, which resulted in highest Chl content, water and energy use efficiency [54] . The fact that red light supplemented with blue light which increased productivity is linked to enhanced photosynthetic performance has also been reported in many other plant species.…”

“…In addition to red light, many studies have manipulated the proportion of blue light necessary for normal plant growth [13,15,16,39,48] . Supplementing appropriate amount of blue light to red light results in dramatic effects on the morphology and anatomy structure [13,18,23,[48][49][50] , chloroplast structure [31,48,51,52] and photosynthetic performance [18,36,39,[53][54] .…”