Impact of zinc oxide nanoparticles and iron on Stevia rebaudiana Bertoni growth, nutrient uptake, and bioactive compounds under in vitro conditions

Abstract

Abstract The experiment investigated the effects of different levels of zinc oxide nanoparticles (ZnONPs) (0, 10, 20, and 30 mg/L) and iron sulfate (13.9, 27.8, and 55.6 mg/L) on morphological and physiological responses of Stevia rebaudiana Bertoni plant under in vitro conditions. Results indicated that the combined application of ZnONPs at 10 mg and iron at 27.8 mg led to the highest increase in shoot number, height, and biomass, showing a respective rise of 17.37%, 39.66%, and 45.02% compared to control cultures. The highest pigment content and tissue antioxidant activity (83.48%) was observed with the combined presence of 10 mg/L ZnONPs and 27.8 mg/L iron. As ZnONP concentration increased in the culture medium, the combined effect on lipid peroxidation rate became more pronounced. The impact of ZnONPs on phenolic compound production varied depending on the specific substance. The iron content of shoots increased significantly by 41.11% under the influence of 27.8 mg/L iron and 10 mg/L ZnONP compared to control cultures. Interaction effects of treatments at various levels resulted in increased zinc content in shoots, peaking at 27.8 mg/L iron when ZnONP reached 20 mg/L, representing a 56.28% increment over control levels before slightly decreasing. The most increases in stevioside and rebaudioside were observed with the combination of 10 mg/L ZnONP and 27.8 mg/L iron, showing enhancements of 75.04% and 63.08%, respectively. These findings suggest that ZnONPs could stimulate the growth and enhance the bioactive components of stevia plants, making them a viable option as elicitors in in vitro batch cultures.