Low levels of TiO 2 -nanoparticles interact antagonistically with Al and Pb alleviating their toxicity.

The contamination and bioavailability of deleterious metals in arable soils significantly limits crop development and yield. Aiming at mitigating Pb- and Al-induced phytotoxicity, this work explores the use of P25 titanium dioxide nanoparticles (nTiO ₂ ) in soil amendments. For that, Lactuca sativa L. plants were germinated and grown in the presence of 10 ppm Pb or 50 ppm Al, combined or not with 5 ppm nTiO ₂ . Growth parameters, as well as endpoints of the redox state [cell relative membrane permeability (RMP), thiobarbituric acid reactive substances content, total phenolic content and photosynthesis (sugars and pigments levels, chlorophyll a fluorescence and gas exchange), were evaluated. Concerning Al, nTiO ₂ treatment alleviated the impairments induced in germination rate, seedling length, water content, RMP, stomatal conductance (g _s ), intercellular CO ₂ (C _i ), and net CO ₂ assimilation rate (P _N ). It increased anthocyanins contents and effective efficiency of photosystem II (Φ _PSII ). In Pb-exposed plants, nTiO ₂ amendment mitigated the effects in RMP, P _N , g _s , and C _i . It also increased the pigment contents and the transpiration rate (E) comparatively to the control without nTiO ₂ . These results clearly highlight the high potential of low doses of nTiO ₂ in alleviating metal phytotoxicity, particularly the one of Pb. Additionally, further research should explore the use of these nanoparticles in agricultural soil amendments.
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