Form of Silica Improves Yield, Fruit Quality and Antioxidant Defense System of Tomato Plants under Salt Stress

Tomato crop is valuable worldwide thanks to its commercial and nutritional value, which plays a very important role in the human diet. However, in arid areas, tomato crops can be found with high salt content. Salinity is a major problem for agriculture, as it decreases productivity, lowers economic yields, and induces soil erosion. The application of silicon has been observed to increase tolerance to abiotic stress and specifically to salt stress. Therefore, the aim of this study is to evaluate the application of K 2 SiO 3 and SiO 2 nanoparticles (SiO 2 NPs) on the growth, antioxidant content, and tolerance to saline stress of tomato plants. Plant growth, fruit quality parameters (pH, titratable acidity, total soluble solids, firmness), antioxidant capacity (ABTS, DPPH), enzymatic (SOD, PAL, APX, CAT, GPX) and non-enzymatic (flavonoids, phenols, vitamin C, β-carotene, lycopene) antioxidant compounds, chlorophylls, proteins, and H 2 O 2 were evaluated. The application of SiO 2 NPs at 500 mg L −1 had positive effects on the plants that were not subjected to stress, increasing the average fruit weight, fruit yield, and chlorophyll, phenol, glutathione, and GPX activity. Meanwhile, in plants under salt stress, it helped to maintain the concentration of chlorophylls, GSH, PAL activity, and vitamin C. The application of SiO 2 NPs is more effective than K 2 SiO 3 at inducing positive responses in tomato plants subjected to stress by NaCl.