Titanium dioxide nanocrystals (TiO2 NCs), through their photocatalytic activity, are able to generate charge carriers and induce the formation of various reactive oxygen species (ROS) in the presence of O2 and H2O. In general, much work still needs to be done to unravel the delicate balance between beneficial and detrimental effects of TiO2 NPs on eukaryotic cells. These are affected also on land and though some potential benefit might exist when it comes to agricultural plants, TiO2 can also lead to cellular damage and should be considered when it comes to transfer along the food chain towards human consumers. Adversities are also reported from other aquatic organisms, including primary producers. In aquatic environments, much has been done in understanding the impact of TiO2 on bivalves, in which an effect on hemocytes, among others, is reported. On the other hand, the capability of TiO2 NPs to induce cell death has found application in photodynamic therapy of cancers. TiO2 NPs exhibited toxicity in multiple organs in animals, generating potential health risks also in humans, such as developing tumors or progress of preexisting cancer processes. TiO2 NPs are considered toxic due to their production of reactive oxygen species (ROS), which can, among others, lead to cellular damage, inflammatory responses, and differences in gene expression. Nanoparticulate TiO2 (TiO2 NPs) is a widely used material, whose potential toxicity towards eukaryotic cells has been addressed by multiple studies. The positive effect of the Ag-TiO 2 NPs treatment could be associated to the generation of reactive oxygen species, antimicrobial activity, increased biochemical attributes, enzymatic activity or improvements in water absorption. The inoculation with NPs of 8.3 nm size and lowest concentration was related to the highest average ROE value, 24.6 ± 0.2%, while the control group was 20.2 ± 0.2%. The statistical trend indicated that the application of the Ag-TiO 2 NPs suspension of lowest concentration and smallest particle size could be a promoting agent of the growth and development of these plants. The analysis of variance showed that the dependent variable (plant growth) could be affected by the evaluated factors (concentration and size) with significant differences. Samples of TiO 2 powder with particle size between 9 and 43 nm were used to quantify the germination rate, which served to determine a narrower size range between 7 and 26 nm in the experiments with Ag-TiO 2 NPs the presence of Ag in TiO 2 powder samples was confirmed by energy-dispersive X-ray spectroscopy. The photosynthetic activity of the spinach plants was estimated through the quantification of the Ratio of Oxygen Evolution (ROE) by the photoacoustic technique.

These NPs were obtained by means of the sol-gel method and heat treatment the resulting powder material was characterized using X-ray diffraction and scanning electron microscopy and the influence of these NPs on plants was measured by estimating the germination rate, monitoring morphological parameters and evaluating phytotoxicity. This is an important crop for human consumption with high nutritional value due to their low calorie and fat content, providing various vitamins and minerals, especially iron. In this work, the effect of the inoculation of silver-incorporated titanium dioxide nanoparticles (Ag-TiO 2 NPs) in spinach seeds was evaluated on certain growth, physiology and phytotoxicity parameters of the plants.

Spinach seedlings