Stevia rebaudiana (Bert.) Bertoni cultivated under different photoperiod conditions: Improving physiological and biochemical traits for industrial applications

Abstract

Stevia rebaudiana is an important industrial crop due to the accumulation of high amounts of steviol glycosides (SG - natural sweeteners) in its leaves. S. rebaudiana cultivation has faced some pushbacks since this species is highly responsive to environmental factors, such as light availability. Sixty days after sowing, plants were transferred to different photoperiod conditions (12/12 h, 15/9 h, and 16/8 h of light/dark). Leaf extracts of plants growing at the 16/8 h photoperiod showed greater accumulation of antioxidant-like metabolites as compared to the other two photoperiods, which might be explained by the total phenolic content of the extracts. Additionally, plants growing at the 16/8 h photoperiod showed increased SOD activity as compared to plants growing at the 15/9 h photoperiod, which in turn showed higher SOD activity than plants growing at the 12/12 h photoperiod. It seems that SOD isoforms act synergically with phenolic compounds to prevent possible damages caused by reactive oxygen species that are produced in plants growing at long-day photoperiods. Sixteen metabolites were identified by Nuclear Magnetic Resonance in the leaf and stem extracts. Alanine, formate, choline, kaempferol-3-O-β-d-glucopyranoside-7-O-α-l-rhamnopyranoside, and gallic acid seems to contribute to maintain stevia homeostasis under unfavorable conditions. Furthermore, the accumulation of SGs and other bioactive compounds in S. rebaudiana in response to different photoperiods provides important leads for the improvement of its large-scale cultivation, as well as for the extraction and purification of phytochemicals with industrial interest.