TiO2 nanopowder has been prepared with aqueous chemical synthesis for use in agriculture. A commercial nanopowder was taken for comparison. A comprehensive study of the phase composition, morphology, and structure of both nanopowders was carried out using methods of X-ray phase analysis, Raman spectroscopy, scanning electron microscopy, ultra-small-angle and small-angle neutron scattering, and low-temperature nitrogen adsorption. A comparison of the photocatalytic activity of these powders was carried out. Aqueous suspensions of these powders were used for the pre-sowing treatment of white cabbage seeds. A positive effect of suspensions of both titanium dioxide powders at a concentration of 0.3 g/l on the germination and biometric characteristics of plant seedlings of cabbage seedlings was revealed. As a tendency, we can note the more beneficial effect of the synthesized powder, which has a high specific surface area and porosity, is weakly crystallized in the anatase phase, and has a three-level fractal structure. No direct effect of photocatalytic activity on the germination and growth characteristics of plant seedlings was found.