Effects of light intensity and photoperiod on improving steviol glycosides content in Stevia rebaudiana (Bertoni) Bertoni while conserving light energy consumption
2017
Yoneda, Yuki | Shimizu, Hiroshi | Nakashima, Hiroshi | Miyasaka, Juro | Ohdoi, Katsuaki
Stevia rebaudiana (Bertoni) Bertoni accumulates steviol glycosides (SGs) which are natural sweeteners. Leaf extracts have been widely used as a food additive because the strong sweetness intensity of SGs that is 300 times sweeter than sucrose. S. rebaudiana is a short-day (SD) perennial plant, and some studies claim that long-day (LD) treatment affects SGs accumulation. However, the optimal and detailed light regime required to increase total SGs content remains controversial. We analyzed the effect of various light intensities and day lengths to determine optimal light treatment for SGs accumulation with minimal energy consumption in growth chambers. Night-interruption (NI) treatments in conjunction with 8h photoperiod increased leaf biomass to amounts observed under LD conditions, and resulted in higher SGs content than that observed under 12h photoperiod while minimizing energy consumption. In addition, end-of-day far-red (EOD-FR) treatment for 15min at 50μmolm−2s−1 was associated with transcription upregulation of the SGs-related gene UGT85C2, higher SGs content, and similar leaf biomass compared to that observed under 16h photoperiod. These light treatments offer great potential for energy-efficient increases in S. rebaudiana total SGs content when plants are grown in a greenhouse or in the field with supplemental lights.
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