Internalization and Phytotoxic Effects of CuO Nanoparticles in <i>Arabidopsis thaliana</i> as Revealed by Fatty Acid Profiles

Abstract

Internalization and phytotoxic effects of CuO nanoparticles ( n CuO) in plants were studied at the cellular level. Arabidopsis thaliana was hydroponically challenged by n CuO (100 mg/L), as compared to Cu 2+ ions (1.2 mg/L), to account for n CuO dissolution for 96 h and 28 days to monitor Cu accumulation in the plant as well as the fatty acid (FA) profiles of the plant cell membrane. Under the same growing conditions, the n CuO exposure resulted in more Cu accumulation than did the Cu 2+ exposure. Multiple microscopic techniques confirmed the internalization and sequestration of n CuO in root cell vacuoles, where transformation of Cu(II) to Cu(I)Cl occurred. Short and long exposures (96 h versus 28 days) to both n CuO and Cu 2+ elevated FA saturation degrees in plant cells through oxidative stress, as verified by in situ detection of superoxide radicals, with conversions mostly from C18:3, C16:3, and C18:2 to C16:0. Only the long exposure to n CuO significantly brought about an additional elevation of FA saturation degree in root cells. These results demonstrated that the acute effects of plant exposure to n CuO were mainly produced from the stress of Cu 2+ ions released from n CuO dissolution, while the chronic effects in roots were significantly developed by the n CuO particle stress. The findings in this work are novel and may offer significant implications in better understanding nanoparticle-induced phytotoxicity and potential risks in ecosystems.