羥四環素對浮萍抗氧化能力之研究

羥四環素 (OTC) 是自然水域中存在最普遍的抗生素之一，考量到OTC毒性對水域中生物的危害，需要設法減少OTC在水域中的濃度，對此可利用浮萍透過植生復育技術完成此目的，因此本試驗的目的即是確認浮萍對於OTC毒性的生理反應，希望可供未來關於浮萍清除OTC之研究基礎所用。試驗選擇6種濃度 (0, 0.05, 0.1, 0.5, 1以及2 ppm) 連續處理5天，另外使用生長半抑制濃度進行時間序列之處理 (0, 12, 24, 48, 72以及120小時)，觀察浮萍 (Lemna aequinoctialis) 對於OTC慢性以及急性毒性的生理反應。在慢性毒性的試驗結果中，2 ppm的OTC明顯抑制浮萍的生長，葉綠素b以及總葉綠素的含量在所有試驗組中均顯著下降。活性氧物質 (Reactive oxygen species, ROS) 以及丙二醛 (Malondialdehyde, MDA) 含量在所有試驗組中均未產生顯著的變化。在抗氧化系統方面，除了抗壞血酸過氧化酶 (APX) 在0.1 ppm的試驗組中活性有顯著的上升以外，其餘三種抗氧化酵素的活性均沒有產生顯著的變化，而抗氧化物質抗壞血酸 (ASC) 在0.1 ppm的試驗組中有顯著的增加。在急毒性生理反應方面，浮萍的生長半抑制濃度為150 ppm，在處理48小時後，浮萍的MDA含量會明顯增加，72小時後H2O2含量顯著增加，96小時後葉綠素a以及總葉綠素含量顯著下降。抗氧化酵素方面，過氧化氫酶 (CAT) 活性在48小時升至最高，隨後開始下降，超氧化物歧化酶 (SOD) 以及穀胱甘肽還原酶 (GR) 有相似的表現，在處理前期活性都有下降的趨勢。抗氧化物質抗壞血酸 (ASC) 在72、96以及120小時具有最高的含量。試驗結果表明，OTC的毒性雖然會抑制浮萍的生長，但浮萍能夠靠著調節抗氧化系統，特別是ASC含量來減緩氧化損傷，以確保自身的存活。

關鍵字

羥四環素；抗氧化系統；浮萍；氧化逆境

並列摘要

Oxytetracycline (OTC) is one of the most common antibiotics in natural waters. Considering the harm of OTC toxicity to organisms in the waters, it is necessary to reduce the concentration of OTC in the waters. This can be done by using duckweed through phytoremediation technology. Therefore, the purpose of this experiment is to confirm the physiological response of duckweed to OTC toxicity, hoping to be based for future research on duckweed removal of OTC. Experiment selected six concentrations (0, 0.05, 0.1, 0.5, 1 and 2 ppm) for continuous treatment for 5 days, and using the growth half-inhibitory concentration (IC50) treatment for 0, 12, 24, 48, 96 and 120 h, in order to observe the physiological response of duckweed (Lemna aequinoctialis) to OTC chronic and acute toxicity. In response to chronic toxicity, 2 ppm of OTC significantly inhibited the growth of duckweed, and the content of chlorophyll b and total chlorophyll decreased significantly in all experimental groups. The contents of ROS and MDA did not change significantly in all experimental groups. In antioxidant system, except for ascorbate peroxidase (APX), which showed a significant increase in the experimental group at 0.1 ppm, there were no significant changes in the activities of the other antioxidant enzymes, while the ascorbate (ASC) increased significantly in the experimental group at 0.1 ppm. In acute toxicity physiological response, the IC50 of 150 ppm for duckweed growth. After 48 hours of treatment the content of MDA was significantly increased, whereas H2O2 content was significantly increased at 72 hours, while the content of chlorophyll a and total chlorophyll decrease significantly at 96 hours. In antioxidant system, catalase (CAT) activity increased to the highest at 48 hours, and then to decrease, whereas superoxide dismutase (SOD) and glutathione reductase (GR) showed similar behaviors, which a activity decreasing trend in the early treatment, while ASC had the highest levels at 72, 96 and 120 hours. The experimental results show that the toxicity of OTC can inhibit the growth of duckweed, and duckweed can palliation oxidative damage by regulating the antioxidant system, especially the ASC content, to ensure own survival.