Ameliorated Morpho-Physiological Response of Stevia Under the Influence of Variable LEDs Inside Plant Factory System

The most prevalent light source for different plant species being cultivated under ex situ conditions is fluorescent lighting. Nevertheless, other light sources, such as light-emitting diodes (LEDs) in different colors, have shown to be more effective for such controlled conditions. In the present research, we have assessed the impact of variable light qualities on stevia (Stevia rebaudiana Bert.) seed germination and plant growth inside regulated environmental conditions. For this intent, red (RD), white (WH), blue (BL), and the different combinations of RD and BL LEDs were arranged in the plant factory system (PFS). Interestingly, it was found that the fresh weight (FW) and dry weight (DW) of leaves per plant (10.8 and 1.9 g) and FW and DW of roots per plant (2.7 and 0.4 g) measured to be maximum under RD:BL (1:1) exposure. The plants grown in PFS illuminated with RD:BL (8:2) LEDs showed maximum photosynthesis rate (8 μmol CO₂/m²/s), chlorophyll a content (1.1 µg/ml), and stomata length and width in comparison to other LED exposures. Stomatal conductance and transpiration rate recorded maximum at 200 μmol/mol of CO₂ concentration in plants raised under RD:BL (1:1) with 275 and 2.3 mmol H₂O/m²/s, respectively. RuBisCO activity was recorded to be maximum under WH LED (0.17 µg/g). It was observed that a combination of RD and BL LEDs is more suitable for improved biomass, photosynthesis rate, chlorophyll contents, and stomatal conductance in the PFS than that of other individual light sources. The application of such biomass enhancement approach described in the present work might be advantageous for ameliorated steviol glycosides accumulation in stevia.