Titanium dioxide nanoparticles (TiO2-NPs) effect on germination and morphological parameters in alfalfa, tomato, and pepper

Titanium dioxide nanoparticles are used in different processes, derived from this their presence in wastewater is common, concentrating in residual sludge. These residues are used as agricultural soil improvers, being a source of crop exposure. In this study, the effect of TiO2-NPs (450, 900, and 1800 mg L-1) on the germination of alfalfa, tomato, and pepper seeds was evaluated. The germination parameters were not different (p > 0.05) except for, the seed vigor index in alfalfa and pepper, and the mean germination time in tomato. The germination index was below 80% in 450 mg L-1 in tomato, which showed moderate phytotoxicity. Morphological modifications with differences (p < 0.05) were found in the three crops, mainly in the root. In tomatoes, the length of the main root, root hairs, and the width of the root tip were reduced but increased the width of the main root, piliferous zone, and the length of root hairs were. For alfalfa, root length and number of secondary roots augment. However, the stem, root tip width, and root villi were reduced. Finally, for pepper, the length, and width of the root and the piliferous zone were modified. Additionally, a concerning trend has been observed in the length of root hairs. TiO2-NPs affected germination and morphology in alfalfa, tomato and pepper seeds differently. Tomato was most negatively affected, with reduced root length and width. Alfalfa showed mixed effects, with positive impacts on some parameters but negatives on others. Pepper seeds responded positively overall, with improved germination and root length, despite some impacts on root morphology.