Effects of Light Conditions on the Leaf Growth and Steviol Glycoside Yields of Hydroponically Cultivated Stevia Across Growth Stages

Abstract

Extracts of Stevia rebaudiana are rich in sweet-tasting steviol glycosides (SG), which are widely valued as natural sweeteners. This study investigated the effects of different light conditions on stevia growth and SG production across growth stages using a controlled hydroponic system. Four light conditions were introduced at a low photosynthetic photon flux density of 50 mu mol<middle dot>m-2<middle dot>s-1. Stevia growth was divided into four stages, and leaf weight and SG yield were analyzed. Red light resulted in the highest leaf fresh weights at 23.53 g<middle dot>plant-1, whereas green light resulted in the lowest at 17.15 g<middle dot>plant-1, marking a difference of 37.2%. However, green light performed the highest total SG content (LSG) at 190.68 mg<middle dot>g-1 and total SG yield (YSG) at 39.24 g<middle dot>m-2, compared to the lowest LSG under red light at 108.68 mg<middle dot>g-1 and YSG at 24.76 g<middle dot>m-2, derived differences of 75.45% and 58.48%, respectively. These results suggest a trade-off between vegetative growth and SG synthesis. Red light is optimal for early-stage biomass accumulation, while green light and blue light treatments during the last two stages, respectively, may enhance overall SG production. Consequently, the results offered insights into commercial stevia cultivation and the production of SG.