RESUMO
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 (nTiO2) 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 nTiO2. 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, nTiO2 treatment alleviated the impairments induced in germination rate, seedling length, water content, RMP, stomatal conductance (gs), intercellular CO2 (Ci), and net CO2 assimilation rate (PN). It increased anthocyanins contents and effective efficiency of photosystem II (ΦPSII). In Pb-exposed plants, nTiO2 amendment mitigated the effects in RMP, PN, gs, and Ci. It also increased the pigment contents and the transpiration rate (E) comparatively to the control without nTiO2. These results clearly highlight the high potential of low doses of nTiO2 in alleviating metal phytotoxicity, particularly the one of Pb. Additionally, further research should explore the use of these nanoparticles in agricultural soil amendments.
