Aluminum oxide (Al₂O₃) nanoparticles (NPs) are among the nanoparticles most used industrially, but their impacts on living organisms are widely unknown. We evaluated the effects of 50–1000 mg L^-1 Al₂O₃ NPs on the growth, metabolism of lignin and its monomeric composition in soybean plants. Al₂O₃ NPs did not affect the length of roots and stems. However, at the microscopic level, Al₂O₃ NPs altered the root surface inducing the formation of cracks near to root apexes and damage to the root cap. The results suggest that Al₂O₃ NPs were internalized and accumulated into the cytosol and cell wall of roots, probably interacting with organelles such as mitochondria. At the metabolic level, Al₂O₃ NPs increased soluble and cell wall-bound peroxidase activities in roots and stems but reduced phenylalanine ammonia-lyase activity in stems. Increased lignin contents were also detected in roots and stems. The Al₂O₃ NPs increased the p-hydroxyphenyl monomer levels in stems but reduced them in roots. The total phenolic content increased in roots and stems; cell wall-esterified p-coumaric and ferulic acids increased in roots, while the content of p-coumaric acid decreased in stems. In roots, the content of ionic aluminum (Al⁺³) was extremely low, corresponding to 0.0000252% of the aluminum applied in the nanoparticulate form. This finding suggests that all adverse effects observed were due to the Al₂O₃ NPs only. Altogether, these findings suggest that the structure and properties of the soybean cell wall were altered by the Al₂O₃ NPs, probably to reduce its uptake and phytotoxicity.

氧化铝 (Al ₂ O ₃ ) 纳米颗粒 (NP) 是工业上最常用的纳米颗粒之一，但它们对生物体的影响却鲜为人知。我们评估了50–1000 mg L ^-1 Al ₂ O ₃ NPs对大豆植物生长、木质素代谢及其单体组成的影响。 Al ₂ O ₃ NPs不影响根和茎的长度。然而，在微观水平上，Al ₂ O ₃ NPs改变了根部表面，导致根尖附近形成裂纹并损坏根冠。结果表明，Al ₂ O ₃ NPs被内化并积累到根部的细胞质和细胞壁中，可能与线粒体等细胞器相互作用。在代谢水平上，Al ₂ O ₃ NPs增加了根和茎中可溶性和细胞壁结合的过氧化物酶活性，但降低了茎中苯丙氨酸解氨酶活性。在根和茎中也检测到木质素含量增加。 Al ₂ O ₃ NPs增加了茎中的对羟基苯基单体水平，但降低了根中的对羟基苯基单体水平。根、茎中总酚含量增加；根中细胞壁酯化的对香豆酸和阿魏酸含量增加，而茎中对香豆酸含量减少。在根中，铝离子 (Al ⁺³ ) 的含量极低，相当于以纳米颗粒形式施用的铝的 0.0000252%。这一发现表明观察到的所有不利影响均仅归因于 Al ₂ O ₃ NP。 总而言之，这些发现表明，Al ₂ O ₃ NPs改变了大豆细胞壁的结构和特性，可能是为了减少其吸收和植物毒性。