Effect of low temperatures on the total protein, proline and the activity of some antioxidant enzymes of Stevia rebaudiana Bertoni

Nowadays, natural sweeteners, especially for people with diabetes have attracted great attention. Stevia rebaudiana,Asteraceae, have Glycoside terpens including Stevioside, Dudoside and Rebaudioside which are 300 times sweeter than sucrose is very important, economically and scientifically. To investigate the impact of low temperatures on the total protein, proline and the activities of some enzymatic antioxidants of stevia, a completely random factorial design experiment with three levels of temperatures 25 (control), 15 and 5°C in three replications was conducted. According to the results, stevia leaves showed no significant differences in total protein, proline content and the activity of the examined antioxidant enzymes including SOD, APX, POD, PPO, under low temperatures of 15 and 5°C. Therefore, it can be concluded that the temperatures of 15 and 5°C cannot create stress for Stevia plants, and so probably this plant is physiologically tolerant at this cold levels. Also, apparently the treated plants were not significantly different compared to controls.