TiO2 nanoparticles effects on morphology and physiology of Artemisia absinthium L. under salinity stress

Abstract

Providing strategies for coping and managing NaCl salinity stress is the goal of many researches. Titanium dioxide nanoparticles (TiO2 NPs) are widely used as photo-catalytic agents due to their strong oxidative properties, optical stability, lack of toxicity, cheapness and availability. Here, the effects of various concentrations of NaCl salinity and titanium dioxide nanoparticles on certain growth factors of the shoot and root, the protein content, activities of catalase, guaiacol peroxidase, superoxide dismutase and polyphenol oxidase enzymes in Artemisia absinthium L were studied. SDS–PAGE was used to analyze the protein expression of A. absinthium at different levels of NaCl salinity stress and TiO2 nanoparticles treatment. All the experiments were performed as a factorial in a completely randomized design in three replications. Data were analyzed using SPSS software. We found that the increase in the concentration of TiO2 NPs up to 20 mg L−1 leads to the enhancement in the length and dry/fresh weights of roots, while there is a reverse pattern for all the traits with the concentration of 30 mg L−1 of nanoparticles. Moreover, the results showed a significant enhancement in the antioxidant activity of catalase, peroxidase, superoxide dismutase, polyphenol oxidase and guaiacol peroxidase enzymes and also protein content in some salinity-stressed plants and those were treated with various concentrations of titanium dioxide nanoparticles in comparison with the control group. According to protein molecular weight in NCBI and SDS–PAGE, some isoenzymes were found for each of the evaluated antioxidant enzymes, and their expression highly differed among the evaluated samples. The increase in isoenzymes’ band intensity was related to the increase in their protein expression, isoenzymes accumulation in the cells or both of them. In some cases, enzymes’ activities were increased, but there was no change in the related band intensity in the SDS–PAGE. It seems that the increase in enzymes activities could be due to the effect of nanoparticles on the enzyme’s active site. Therefore, the increase in antioxidant enzymes activities was related to increase in gene expression, enzyme activity or both processes. In this study, the highest concentrations of the nanoparticles (30 mg L−1) had the negative effects on the NaCl salinity-treated samples and in several cases decreased growth of the shoot and root, proteins content and enzymes activities.