Accumulation, translocation and impact of TiO2 nanoparticles in wheat (Triticum aestivum spp.): Influence of diameter and crystal phase

• Published in: The Science of the total environment 2012-08, Vol.431, p.197-208
• Main Authors: Larue, Camille, Laurette, Julien, Herlin-Boime, Nathalie, Khodja, Hicham, Fayard, Barbara, Flank, Anne-Marie, Brisset, François, Carriere, Marie
• Format: Article
• Language: English
• Subjects: Animal, plant and microbial ecology; Applied ecology; Biological and medical sciences; Crystals; Ecotoxicity; Ecotoxicology - methods; Ecotoxicology, biological effects of pollution; Environmental Pollutants - pharmacokinetics; Environmental Sciences; Fundamental and applied biological sciences. Psychology; General aspects; Germination; Microscopy, Electron, Transmission; Nanoparticles; Particle Size; Plant; Plant Leaves - metabolism; Plant Roots - metabolism; Plant Shoots - metabolism; Plants (organisms); Roots; Rutile; Spectrometry, X-Ray Emission - methods; Thresholds; Tissue Distribution; Titanium - pharmacokinetics; Titanium dioxide; Titanium dioxide nanoparticle; Triticum - growth & development; Triticum - metabolism; Triticum aestivum; Wheat; X-ray absorption spectroscopy; X-ray fluorescence microscopy
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2012.04.073

Intensive production of TiO2 nanoparticles (TiO2-NPs) would lead to their release in the environment. Their ecotoxicological impact is still poorly documented, while their use in commercial goods is constantly increasing. In this study we compare root accumulation and root-to-shoot translocation in wheat of anatase and rutile TiO2-NPs with diameters ranging from 14nm to 655nm, prepared in water. NP distribution in plant tissues was mapped by synchrotron-radiation micro-X-ray fluorescence, observed by transmission electron microscopy and quantified in the different compartments of plant roots by micro-particle-induced X-ray emission. Our results provide evidence that the smallest TiO2-NPs accumulate in roots and distribute through whole plant tissues without dissolution or crystal phase modification. We suggest a threshold diameter, 140nm, above which NPs are no longer accumulated in wheat roots, as well as a threshold diameter, 36nm, above which NPs are accumulated in wheat root parenchyma but do not reach the stele and consequently do not translocate to the shoot. This accumulation does not impact wheat seed germination, biomass and transpiration. It does not induce any modification of photosynthesis nor induce oxidative stress. However exposure of wheat plantlets to the smallest NPs during the first stages of development causes an increase of root elongation. Collectively, these data suggest that only the smallest TiO2-NPs may be accumulated in wheat plants, although in limited amounts and that their impact is moderate. ► TiO2-NP diameter, but not crystallinity, influences their transfer in plant tissues. ► Wheat roots accumulate TiO2-NPs with diameter up to 36nm but not 140nm TiO2-NPs. ► TiO2-NPs with diameter lower than 36 nm are translocated from wheat root to shoot. ► A 100 mg/L TiO2-NP wheat root exposure leads to Ti root content up to 110μg/gd.wt. ► Exposure of wheat to the smallest TiO2-NP induces increased root elongation.