Changes on antioxidant system in cadmium-stressed tomato (Lycopersicum solanum L.) plants treated with nanosilica and 24-Epibrassinolide

In this experimental study, a completely randomized design carried out on tomato plants with two levels of cadmium chloride, (0 and 100 μM), two levels of 24-epiBrassinolide (0 and 0.75 μM) and two levels of silica nanoparticles (0 and 50 mg/l). Cadmium stress significantly decreased growth parameters, chlorophyll content as well as increased content of phenolic compounds, malondialdehyde, hydrogen peroxide and increased cadmium accumulation in tomato leaves. Results showed that pretreatment of silica nanoparticles resulted in improved growth characteristics and increased polyphenol oxidase activity in the leaf under stress. Decrease in content of phenolic compounds, malondialdehyde and hydrogen peroxide was observed after cadmium accumulation in this treatment. Pretreatment of 24-epiBrassinolide also decreased the content of phenolic compounds, malondialdehyde, hydrogen peroxide, as well as increased shoot fresh weight, root length to stem length ratio, polyphenol oxidase and catalase activity, and decreased cadmium accumulation in the leaf under stress. Interaction effects of pretreatment of silica and 24-epiBrassinolide nanoparticles had significant effect on malondialdehyde and hydrogen peroxide content as well as increase in root dry weight, polyphenol oxidase activity and decrease in cadmium accumulation in leaves. Silica nanoparticles and 24-epiBrassinolide nanoparticles were found to improve growth and attenuation of cadmium stress by improving the biochemical properties and antioxidant system of tomato plants.