Wheat chronic exposure to TiO 2 -nanoparticles: Cyto- and genotoxic approach.

This study investigates the phytotoxicity of chronic exposure (up to 20 d) of different TiO2 nanoparticles (TiO2 -NP) concentrations (5, 50, 150 mg L-1 ) in Triticum aestivum. Germination was not affected by TiO2 -NP exposure and seedling shoot length (3 d) was enhanced. Contrarily, plants' shoot growth (20 d) was impaired. Effects on membrane permeability and total antioxidant capacity in TiO2 -NP chronic exposure were organ dependent: increased in leaves and decreased in roots. Roots also showed lower levels of lipid peroxidation. Flow cytometry revealed no changes in ploidy levels as well as in the cell cycle dynamics for both organs. However, TiO2 -NP induced clastogenic effects in roots with increases in micronucleated cells in root tips in a dose dependent manner. Also, increases of DNA single/double strand breaks were found in leaves, and effects were similar to all doses. Ti uptake and translocation to leaves were confirmed by ICP-MS, which was dependent on NP concentration. Overall, these data indicate that TiO2 -NP phytotoxicity is more severe after longer exposure periods, higher doses and more severe for shoots than roots. The observed effects are a result of both direct and indirect (oxidative stress and/or water imbalances) action of TiO2 -NP. Additionally, results highlight the negative impact that TiO2 -NP may have on crop growth and production and to the risk of trophic transfer.