Attenuation of lead genotoxicity in Glycine max by adsorbent nanosized titanium dioxide using phenotypic, cytogenetic and DNA status bioassays
Genotoxicity caused by heavy metals can negatively affect vital processes of crop plants, though remedial measures can be used to reduce such damage. We examined the possible stimulatory and phytotoxicity impacts of three nanosized titanium dioxide (nTiO2) doses on soybean (Glycine max) and how adsorption of lead (Pb) onto the surface of nTiO2 may attenuate the toxic action of Pb on soybean by comparing the toxicity of three Pb doses before and after the adsorption process. The exposure time was 48 h. Phenotypic parameters (seedling growth, phytotoxicity, tolerance and vigor indices), cytogenetic tests of pollen grain performance, and DNA status (using flow cytometry, comet assays and analysis of RAPDs) were used as bioassays to assess the effect of the treatments. The optimal nTiO2 dose was 10 mg.L-1 because it i) stimulated and accelerated seedling development parameters, fertility and germination of pollen grains, ii) increased nuclear DNA content and decreased the extent of DNA damage, and iii) generated the maximum number of amplified DNA bands as an indicator for appearances of new DNA bands (genes) more than the control. Doses of nTiO2 higher and lower than the optimal dose resulted in a gradual decline in these parameters, especially the higher dose. The three doses of Pb induced notable inhibitory and genotoxic impacts on all biomarkers used, in a dose-dependent manner. We conclude that the powdered state of optimal dose (10 mg) had a good ability to adsorb Pb onto its surface and consequently mitigated its toxicity. This was evident through the significant amelioration of parameters of each biomarker after application of the three Pb adsorbate solutions on soybean seeds. Therefore, we suggest that stimulatory and adsorbent nTiO2 dose may be used in the future to protect against heavy metal toxicity in economically important plants.