Titanium dioxide (TiO₂) nanoparticles (NPs) are the most widely released nanomaterials in the environment and are considered an emerging contaminant. Although the phytotoxicity mechanism of TiO₂ NPs on plants involves the elevated generation of reactive oxygen species (ROS), it is still not well established in soybean. Herein, we evaluated the effects of 250–1000 mg L⁻¹ TiO₂ NPs on seed germination, growth, content of ROS, lipid peroxidation, and activity of antioxidant enzymes in roots of soybean plants. Our data revealed that up to 1000 mg L⁻¹ TiO₂ NPs did not affect soybean seed germination. Transmission electron microscopy images and determinations of zeta potential and hydrodynamic diameter of a suspension of TiO₂ NPs demonstrated that they form aggregates, favoring their adsorption to the root surface with consequent physical damage. The main deleterious effects noted on roots were reduced cell viability, reduced root hair number, striated aspect of root apexes, and reduced fresh and dry weights of roots. In disagreement with other studies, plant exposure to TiO₂ NPs reduced the level of total ROS and lipid peroxidation, probably due to increased superoxide dismutase (SOD) activity. Altogether, our data suggest that the toxicity mechanism of TiO₂ NPs on soybean roots involves physical damage resulting from their adsorption to the root surface, but not the generation of ROS.

二氧化钛（TiO ₂）纳米颗粒（NPs）是环境中释放最广泛的纳米材料，被认为是新兴污染物。尽管TiO ₂ NPs对植物的植物毒性机制涉及活性氧（ROS）生成量的增加，但在大豆中尚不十分清楚。在本文中，我们评估了250–1000 mg L ^-1 TiO ₂ NPs对大豆植物根中种子萌发，生长，ROS含量，脂质过氧化和抗氧化酶活性的影响。我们的数据表明，高达1000 mg L ^-1 TiO ₂NPs不影响大豆种子发芽。透射电子显微镜图像和TiO ₂ NP悬浮液的Zeta电位和流体力学直径的测定表明，它们形成聚集体，有利于其吸附到根表面，从而造成物理损坏。对根部的主要有害作用是降低细胞活力，减少根毛数，根尖的横纹和减少根的鲜重和干重。与其他研究不同的是，植物接触TiO ₂ NPs降低了总ROS和脂质过氧化的水平，这可能是由于增加了超氧化物歧化酶（SOD）活性所致。总之，我们的数据表明TiO ₂的毒性机理 大豆根部的NP涉及由于其吸附到根部表面而引起的物理损害，但不涉及ROS的产生。