Citric acid and glycine reduce the uptake and accumulation of Fe2O3 nanoparticles and oxytetracycline in rice seedlings upon individual and combined exposure

Abstract

Uptake of nanoparticles and antibiotics by plants is root exudates-dependent, however, the underlying influence processes and mechanisms from different root exudates are rarely investigated. A hydroponic experiment was conducted to investigate the accumulation of Fe₂O₃ nanoparticle (NP) and oxytetracycline (OTC) in rice seedlings, in the absence or presence of citric acid or glycine, acting as components of root exudates. Irrespective of individual or combined exposure of Fe₂O₃ NP and OTC, citric acid and glycine both reduced surface-Fe, surface-OTC, root-OTC, shoot-OTC accumulations with dose-effect relationship. Two exudates increased |ζ| values of NP, which weakened the interactive attraction between NP and root surface and then decreased surface-Fe accumulation. Citric acid and glycine binding with OTC in solution decreased surface-OTC accumulation, and further decreased root-OTC and shoot-OTC accumulations. Combined exposure of two pollutants alleviated the reduction effect of citric acid and glycine on surface-Fe/surface-OTC/root-OTC accumulations due to their high accumulations in combined exposure compared to individual exposure. Although citric acid and glycine promoted TF_root-shoot and TF_surface-root of two pollutants, respectively, they always decreased total rice-Fe and rice-OTC accumulations. Therefore, the presence of root exudates decreased the bioaccumulation of Fe₂O₃ NP and OTC in rice upon their individual and combined exposure through changing their environmental behaviors in rhizosphere.

Keywords: Accumulation; Citric acid; Fe(2)O(3) NP; Glycine; Oxytetracycline (OTC); Rice (Oryza sativa L.).