The cytotoxic targets of anatase or rutile + anatase nanoparticles depend on the plant species

The potential toxicity of nanoparticles (NPs) is under debate. Information about TiO₂ NPs phytotoxicity is still limited partly due to the different TiO₂ NP forms that may be found in the environment. The present work investigated the impact of different TiO₂ NPs forms (rutile and anatase) on germination, growth, cell cycle profile, ploidy level, and micronucleus formation in Lactuca sativa (lettuce) and Ocimum basilicum (basil). Seeds were exposed to anatase (ana) or rutile + anatase (rut+ana) at concentrations 5 - 150 mg dm^-3 for 5 d and after that different parameters were analyzed. Rut+ana showed high potential to impair germination and growth. On the other hand, ana alone showed a positive influence on seedling growth. Despite that, ana induced severe alterations in cell cycle dynamics. Regarding species, basil was more sensitive to TiO₂ NPs cytostatic effects (delay/arrest in G₀/G₁ phase), whereas in lettuce, TiO₂ NPs were more genotoxic (micronucleus formation increase). Finally, we propose that, besides germination and plant growth, cell cycle dynamics and micronucleus formation can be sensitive biomarkers of these NPs.