马拉硫磷及其水解产物对圆瘤浮萍的生长抑制及氧化损伤作用

为了探讨马拉硫磷和主要水解产物对圆瘤浮萍的生长抑制作用及可能的氧化损伤机制,采用静态培养法,研究不同浓度的马拉硫磷及其水解产物二甲基二硫代磷酸酯(DMDTP)、二甲基硫代磷酸酯(DMTP)、二甲基磷酸酯(DMP)对圆瘤浮萍生长、叶绿素含量、叶绿体活性、超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性及丙二醛(MDA)含量的影响。结果表明,暴露7 d后,浓度为100 mg a.i.·L-1处理下的浮萍叶状体生长量与空白对照组无显著性差异;DMDTP、DMTP和DMP对圆瘤浮萍叶状体生长量的半数抑制浓度(7 d-IC50)分别为52.9、45.5和98.0 mg a.i.·L-1。随着试验液中DMDTP、DMTP和DMP浓度的升高,圆瘤浮萍叶绿素含量均明显降低,叶绿体活性则分别表现为诱导-抑制、抑制和抑制效应。在DMDTP、DMTP和DMP胁迫下,脂质过氧化产物丙二醛(MDA)含量明显增加;圆瘤浮萍体内的抗氧化酶系统均受到影响。总体表现为随着DMDTP浓度的增加,SOD活性先降低后升高;DMTP和DMP胁迫下,SOD活性呈现先降后升再降的趋势;POD和CAT活性则随3种水解产物浓度的增加呈现先升后降趋势;这表明抗氧化酶系统对外部胁迫的应答很复杂。马拉硫磷对圆瘤浮萍的毒性较小,其水解产物DMDTP、DMTP和DMP均对圆瘤浮萍的生长产生一定的毒性作用。在实际生产中,应多加关注马拉硫磷水解产物对环境生物的风险评估。

Inhibitory Effect of Malathion and Its Hydrolysates on the Growth of Duckweed (Lemna gibba L.) and Its Relationship with Oxidative Stress

In the present study, we aimed to explore toxic effects of malathion, dimethyl dithiophosphate (DMDTP), dimethyl thiophosphate (DMTP) and dimethyl phosphate (DMP) on Lemna gibba L. Toxic effects of malathion, DMDTP, DMTP and DMP on the growth, relative chlorophyll content and chloroplast activity of Lemna gibba L. were assessed using static methods. At a concentration of 100 mg a.i.^-1, there was no significant difference between malathion and the blank control, while the 7-day IC₅₀ of DMDTP,DMTP and DMP was 52.9, 45.5 and 98.0 mg a.i. L^-1, respectively. Moreover, DMDTP, DMTP and DMP exhibited inhibitory effects on the chlorophyll content in a concentration-dependent manner, while these three compounds exerted induction-inhibition, inhibition and inhibition effects on the chloroplast activity, respectively. Under the stress of DMDTP, DMTP and DMP, the removal system of reactive oxygen species in Lemna gibba L. was affected, and the largest influence was observed in DMP treatment. With the products of lipid peroxide malondialdehyde (MDA) content increasing significantly, SOD activity was first decreased and then increased under the stress of DMDTP, while it was first decreased, then increased and finally decreased again under the stress of DMTP and DMP, suggesting that the cells were damaged. The POD activity and CAT activity showed similar trend, which were first increased and then decreased, indicating that Lemna gibba L.were irreparably damaged under high stress, and the response of antioxidant enzyme system to external stress was complicated. Our data revealed that malathion had less toxicity to Lemna gibba L., while its hydrolysates (DMDTP, DMTP and DMP) exhibited certain toxic effects on the growth of Lemna gibba. Taken together, more attention should be paid to hydrolysates of malathionin environmental risk assessment.