Optimizing Growth through Systematic Evaluation of Salinity, Putrescine, and Sodium Nitroprusside Levels in Stevia rebaudiana

Stevia rebaudiana, a natural sweetener source, has gained significant attention in recent years due to its potential as a sugar substitute with minimal caloric impact. To maximize its cultivation and production efficiency, it is imperative to optimize its growth conditions. In the present study, we performed a pot experiment in the polyhouse of the Department of Horticulture at the Institute of Agricultural Sciences, Banaras Hindu University, Varanasi and investigated the effects of salinity stress (NaCl), exogenous application of putrescine (Put), a polyamine, and sodium nitroprusside (SNP), a donor of nitic oxide, as foliar spray on different morpho-physiological traits such as plant height, number of leaves per plant and SPAD or chlorophyll content in Stevia over different time intervals under in vivo conditions. Our findings revealed that mild salinity stress (15 and 30 mM NaCl) caused a lesser reduction in plant growth characteristics. However, excessive salinity (120 mM NaCl) had adverse effects on plant health, particularly at 15 days. We observed that higher concentrations of Put (1 mM and 2 mM) positively influenced all the studied growth indices as compared to control and NaCl treated plants. This indicates the potential for Put to be used as a growth regulator in Stevia cultivation. Similarly, 150 µM and 200 µM SNP treatments produced best results in Stevia plants by significantly enhancing plant height, leaf number and SPAD at 3, 6, 9, 12 and 15 days. Therefore, SNP can be used as a potential growth promoting agent in Stevia plants. These findings have significant implications for sustainable Stevia cultivation, ensuring a stable supply of natural, low-calorie sweeteners for the food and beverage industry.