The effect cold stress on physiology of Stevia rebaudiana Bertoni under in vitro culture condition

The Stevia rebaudiana is a plant native to Paraguay s semi-humid area and has a medicinal stevil glycosides sweetening compound. Cold stress is one of the most factors limiting the growth and production of plants worldwide, including Stevia. In this study, changes in the activity of antioxidant enzymes, growth parameters such as dry weight, fresh weight, pigments content (chlorophyll a, b, total and carotenoids), total amino acid, proline, hydrogen peroxide (H2O2), flavonoids, anthocyanins, phenolic compounds, carbohydrates, total antioxidant, as well as the rate of peroxidation of lipids in leaf and stem tissues of Stevia under cold stress conditions (5 and 10 œ C). Cold stress can significantly reduce the vegetative growth of the Stevia plant so that the reduction in the steady fresh weight of plants under cold stress was observed. In addition, the amount of H2O2 in leaf and stem of the Stevia plant increased in response to cold stress, which confirms the increase of reactive oxygen kinds (ROS) in the Stevia plant under cold stress. H2O2 accumulation in the stoichi straw and stalks under cold stress was detected by peroxidation of the lipid membranes, so a significant increase in malondialdehyde (MDA) in Stevia plants under cold stress was observed. Stevia plants used different mechanisms to reduce the destructive effects of cold stress. Among these mechanisms, it is possible to increase the activity of antioxidant enzymes. Under cold stress, the activity of the enzymes Catalase (CAT), Ascorbate peroxidase (APX), Guaiacol peroxidase (GPX), Polyphenol oxidase (PPO), Superoxide dismutase (SOD), and Phenylalanine ammonia lipase (PAL), Tyrosine alanine ammonia lyase (TAL) showed a significant increase compared to the control. In addition, total amino acids, proline, anthocyanins, phenol compounds, flavonoids and total antioxidant showed a significant increase compared to the control, as well as temperature low content of photosynthetic pigments (chlorophyll a, b, total and carotenoids) and dry weight decreased the fresh weight of Stevia. Reductions in parameters such as fresh weight, dry weight indicates the sensitivity of this plant to cold stress. Thus, according to the results of this study, it can be concluded that the Stevia plant is susceptible to cold, while also increasing some parameters such as proline, antioxidant enzymes indicating it is the plant that tries to tolerant its tension.

Keywords:

Cold stress , Enzyme , Antioxidants , Stevia rebaudiana×