Nanopowders of titania (TiO_2) features a unique combination of UV-stimulated photocatalytic activity and biocompatibility making ones promising for various biochemical applications, including agrotechnology in respect to the promo-tion of plants germination and growth as well as their protection from different stressors and pathogens. However, the considered target properties strongly depend on such factors as phase composition (i.e. ratio between anatase and rutile poly-morph modifications), particle size (especially in the case of nanoparticles possessing an overall enhanced reactivity and size-depending specific properties) and surface characteristics, particularly presence and content of different centers responsible for acid–base interactions with the environment, incl. aqueous medium. This chapter presents a review of recent researches on the analysis of relationships among these properties of TiO_2 nanoparticles differing in the preparation conditions in order to determine the optimum structural and surface features of titanium dioxide providing the highest photocatalytic activity and certain agricultural applications, incl. the effect of pre-sowing treatment with aqueous suspensions of TiO_2 nanoparticles on the seed germination and plant seedling growth, as well as phytoprotection activity against specific fungal pathogens.