This work aimed to investigate the interaction between salt stress and the application of silicon dioxide-nanoparticles. In this study, gerbera plants grown in soilless culture were supplied with nutrient solutions with different NaCl concentrations (0, 5, 10, 20 and 30 mM) in combination with SiO2-NPs spray (0, 25 and 50 mg · L−1). Exposure of gerbera to salinity increased sodium concentration but decreased potassium and calcium concentrations in leaf as well as stem length/diameter, fresh/dry weight, leaf/flower number, flower diameter and leaf area. It also increased the activities of antioxidant enzymes and electrolyte leakage. Results indicated that SiO2-NPs could improve growth, biochemical and physiological traits. It increased stem thickness but slightly affected stem length. Flower diameter was not affected by salinity rates up to 10 mM of NaCl. However, a significant difference was observed between controls and plants treated with 30 mM of NaCl. Salinity increased the electrolyte leakage (32.5%), malondialdehyde (83.8%), hydrogen peroxide (113.5%), and the antioxidant enzyme activities such as ascorbate peroxidase (3.4-fold) and guaiacol peroxidase (6-fold) where SiO2-NPs activated them more, except for superoxide dismutase. Under salinity (30 mM), the increase in SiO2-NPs (especially at 25 mg · L−1) led to the increase in the uptake of Ca2+ (25.3%) as well as K+ (27.1%) and decreased absorption of Na+ (6.3%). SiO2-NPs has potential in improving salinity tolerance in gerbera. It seems that the sensitivity threshold of gerbera to the salinity was 10 mM and the use of SiO2-NPs is also effective in non-saline conditions.

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