Seed Nanopriming Using Silica Nanoparticles: Effects in Seed Germination and Physiological Properties of Stevia Rebaudiana Bertoni

Abstract Stevia is one of the most dominant medicinal and industrial plants. However, poor seed emergence is the main impediment to obtain a high yield in stevia. Seed priming techniques represent very important strategies to ensure seed productivity. Therefore, this study was carried out to evaluate the effects of different concentrations of Si nutrient sources including bulk silicon dioxide (bSiO 2 ), and two different silica nanoparticles including nSiO 2 (I) and nSiO 2 (II) at concentrations of 1, 5, 10, 25, 50, and 100 ppm in improving emergence, seedling growth, antioxidant enzymes activity, and biochemical attributes. Hence, the effect of seed nanopriming was investigated on germination parameters in stevia using two experiments carried out in a completely randomized design with three replicates. All nanoprimed stevia seedlings had significantly improved germination percentage, root and shoot dry weight, and seedling vigor compared to controls. As well, sucrose concentration, catalase (CAT), and peroxidase (POX) activity were increased by seed nanopriming especially when seeds were primed by nSiO 2 (I) at concentration of 10 ppm, respectively. However, there was a reduction in germination parameters in high concentrations of NPs. On the other hand, bSiO 2 showed less effect on increasing germination, seedling growth, antioxidant activities, and biochemical attributes of stevia compared to nanopriming with nSiO 2 (I), and nSiO 2 (II). Thus, this study proved that seed priming with nSiO 2 (I) at 10 ppm were more effective in improving germination percentage and rate, root and shoot dry weight, biochemical attributes, and enzymes activities (α-amylase, CAT, and POX). The highest concentration of nanopriming led to oxidative damage with increasing H 2 O 2 concentration. It was suggested that seed priming with nSiO 2 (I) at optimal concentrations improved the seed germination by improving the antioxidant system and starch metabolism, which protects plants from oxidative damage.