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

Abstract

Light-emitting diode lamps can allow for the optimization of lighting conditions in artificial growing environments, with respect to light quality, quantity, and photoperiod extension, to precisely manage resources and crop performance. Eruca vesicaria (L.) Cav. was hydroponically cultured under three light treatments to investigate the effect on yield and nutritional properties of rocket plants. A treatment of (W-12h) having a12/12 h light/dark at 600 μmol m−2 s−1 provided by LEDs W:FR:R:B = 12:2:71:15 was compared with two treatments of continuous lighting (CL), 24 h light at 300 μmol m−2 s−1 provided by cool white LEDs (W-CL), and by LED R:B = 73:27 (RB-CL). CL enhanced the growth of the rocket plants: total fresh biomass, leaf fresh weight, and shoot/root ratio increased in W-CL, and leaf dry weight, leaf dry matter %, root fresh and dry weight, and specific leaf dry weight (SLDW) increased in RB-CL. Total carbon content was higher in RB-CL, whereas total nitrogen and proteins content increased in W-12h. Both W-CL and RB-CL increased carbohydrate content in the rocket leaves, while W-CL alone increased the sugar content in the roots. Fibers, pigments, antioxidant compounds, and malic acid were increased by CL regardless of the light spectrum applied. Nitrate was significantly reduced in the rocket leaves grown both in W-CL and RB-CL. Thus, the application of CL with low light intensity can increase the yield and quality value of rocket, highlighting that careful scheduling of light spectrum, intensity, and photoperiod can improve the performance of the crop.

Continuous LED Lighting Enhances Yield and Nutritional Value of Four Genotypes of Brassicaceae Microgreens

“…The effects of light on photosynthetic pigment content varies depending on photoperiod [18,20,30,31], the light spectrum applied during plant growth [13,16,32], and plant species [20]. In this study chlorophyll content of broccoli and radish was not significantly influenced by photoperiod (or DLI) or light quality (Table 2).…”

“…This is important as Chl content is closely associated with human perception of the green pigmentation of leaves [33]. Total Chl content was also negatively affected when CL provided by RB LEDs was applied to rocket leaves [18]. In all LED-CL plants, we observed a reduction in LHCII, and an elevation of the Chl a/b ratio (Figure 2) and the Car/Chl ratio (Figure 3).…”

“…Samuoliene et al [28] also reported similar increases in DW of tatsoi and red pak choi microgreens, as DLI increased. As for the sensitivity of studied plant species to CL, the only available report informs that the efficiency of rocket indoor cultivation was ameliorated by CL without detrimental effects on the yield and quality of edible leaves [18]. A major goal of commercial microgreen producers is to provide growth conditions that maximize as microgreens are sold on a FW basis [29].…”

“…As artificial lighting for growing plants is expensive, the solutions should be aimed to increase the efficiency of energy conversion into yield and quality [18]. One possible way to increase light efficiency in PFAL is extending the duration of lighting period.…”

“…Theoretically, the use of CL provides constant energy for carbon assimilation, meaning larger biomass accumulation and yield [19]. Furthermore, the implementation of a supplemental CL strategy can have a positive economic implication as well [18] if no photo-injury occurs. However, the use of CL on plant cultivation presents a challenge, because plant responses are contradictory and are far from being fully understood.…”