Interactive effects of stress tolerance-inducing compounds on physio-biochemical activities and antioxidant systems of Stevia rebaudiana under salt stress

Stevia rebaudiana is a plant used as a sweetener or in medical applications. This study aimed to investigate the effects of salicylic acid (SA), spermidine (SPD), and methyl jasmonate (MeJA) in specific concentrations with or without salt stress on the plant content. The result shows that the maximum fresh and dry weight was obtained when SA was combined with SPD under salt stress. At the same time, the effect of salt stress alone shows an increase in FRW. The effect of SA alone produced a higher root dry weight of Stevia rebaudiana. Also, we concluded that SPD with salt stress showed a better leave number, followed by SA with salt stress. We concluded that the SPD plus salt stress showed better shoot length and leaf number, followed by the SA plus salt stress. It was also concluded that CAT activity is noticeably stimulated in plants under salt stress by Spd. According to the results, the SOD antioxidant enzyme activity increased when SA was combined with salt stress, followed by MeJA under salt stress. The results showed that salicylic acid application significantly influenced and enhanced total phenolic content. Spd increased chlorophyll a content, whereas MeJA increased chlorophyll b content of plants under salt stress. While combined application of MeJA plus Spd to plants under salt stress show increasing stevioside content, application of SA increased the amount of rebaudiana A.