Degradation of acetochlor by four microbial communities

Four microbial communities capable of degrading acetochlor, designated A, D, E, and J, were obtained from acetochlor-contaminated soil and sludge. Acetochlor at an initial concentration of 55mg/L was completely degraded by the four mixed cultures after 4 days. At 80 mg/L acetochlor, more than 99% degradation was observed with D, 84% with A and E, and 88% with J after 9 days. There are primary eight strains of bacteria in community A, three in community D, E, and J, respectively. No single isolate was able to degrade acetochlor efficiently. The acetochlor biodegradation products were identified by gas chromatography-mass spectrometry. The probable degradative pathways of acetochlor involved dechlorination, hydroxylation, deethoxymethylation, cyclization, carboxylation, and decarboxylation. Propachlor, alachlor, and metolachlor, which are also the main components of the chloroacetanilide herbicide, could be degraded by the four mixed cultures to some degree. Given the high degradation rates observed here, the four mixed cultures obtained may be useful in the degradation processes of acetochlor.     

Haplo-diploid gene expression and pollen selection for tolerance to acetochlor in maize

The objectives of this research were to determine if genes controlling the reaction to the herbicide acetochlor in maize (Zea mays L.) are active during both the haploid and the diploid phases of the life cycle and if pollen selection can be utilized for improving sporophytic resistance. Pollen of eight inbred lines, previously characterized through sporophytic analysis for the level of tolerance to acetochlor, showed a differential reaction to the herbicide forin vitro tube length; moreover, such pollen reactions proved to be significantly correlated (r =0.786^*,df=6) with those of the sporophytes producing the pollen. Pollen analysis of two inbred lines (i.e. Mo17, tolerant, and B79, susceptible) and their single cross showed that thein vitro pollen-tube length reaction of the hybrid was intermediate between those of two parents. An experiment on pollen selection was then performed by growing tassels of Mo17xB79 in the presence of the herbicide. Pollen obtained from treated tassels showed a greater tolerance to acetochlor, assessed asin vitro tube length reaction, than pollen obtained from control tassels. Moreover, the backcross [B79 (Mo17xB79)] sporophytic population obtained using pollen from the treated tassels was more tolerant (as indicated by the fresh weight of plants grown in the presence of the herbicide) than was the control backcross population. The two populations did not differ when grown without the herbicide. These findings indicate that genes controlling the reaction to acetochlor in maize have haplodiploid expression; consequently, pollen selection can be applied for improving plant tolerance.     

柳树叶浸提液对蛋白核小球藻的化感作用

通过对蛋白核小球藻进行细胞密度的测定,分析了不同浓度的柳树(Salix babylonica)叶浸提液对蛋白核小球藻(Chlorella pyrenoidosa)生长和细胞形态的影响。结果表明：柳树叶浸提液对蛋白核小球藻具有化感作用,不同浓度的浸提液化感作用强度不同;作用96 h的半效应浓度(EC₅₀,_{96 h}值)为11.82 g·L^-1,较低浓度(10和20 g·L^-1)浸提液对蛋白核小球藻表现出先抑制后促进的作用特性,而较高浓度（30 g·L^-1）浸提液则始终表现出抑制效果;10、20和30 g·L^-1浸提液对蛋白核小球藻的最大抑制率分别为37.5%、39.3%和56.5%;柳树叶浸提液作用下,部分蛋白核小球藻细胞平均颗粒体积增大,颜色变透明,膨胀后溶解;低浓度浸提液处理组少数细胞聚集在一起,高浓度浸提液处理组细胞大量聚集,形成多细胞群体,多数沉于瓶底,沉降性能增强。     

乙草胺对东北黑土铅形态及生物有效性的影响

通过清洁黑土和污染黑土的形态分级分析和黑土铅对乙草胺的响应实验,对东北黑土铅形态及其乙草胺使用的生物有效性响应进行了研究．结果表明,清洁和污染黑土中的铅均主要以有机质-硫化物结合态铅和残渣态铅这2种生物有效性低的形态为主,而水溶态铅和可交换态铅这2种具生物学活性的铅含量则相对较低．与清洁黑土相比,污染黑土中具生物学活性的铅含量所占总铅含量的比例有所上升．随着农业活动中施入高剂量的乙草胺这一除草剂,黑土中具生物学活性的水溶态和可交换态铅的含量则大幅上升．据分析,其原因是铅在与乙草胺交互作用过程中来自有机质．硫化物结合态铅释放对有效态铅的贡献．     

土壤中乙草胺的微生物降解及其对防除稗草持效性的影响

采用气相色谱法和生物测定法,研究了土壤中乙草胺的微生物降解及其对防除稗草持效性的影响.结果表明,在同样的湿度和温度条件下,当添加到土壤中的乙草胺浓度为125、25和5.0 mg·kg^-1时,相同浓度的乙草胺在非灭菌土壤中的半衰期显著短于灭菌土壤,说明土壤微生物对乙草胺有明显的降解作用.三大主要菌群分离培养物降解实验与上述结果一致.生物测定结果表明,乙草胺在非灭菌土壤中防除稗草的持效期显著短于灭菌土壤,微生物的存在缩短了乙草胺在土壤中的滞留时间,从而降低了乙草胺防除稗草的持效性.     

Tissue-specific expression of rice CYP72A21 induced by auxins and herbicides

Cytochrome monooxygenase P450s (CYPs) comprise one of the largest enzyme families in plants. Some P450s are involved in xenobiotic metabolism: they confer herbicide tolerance and are induced by chemical treatments. We isolated a novel P450 cDNA, CYP72A21 (accession number, AB237166), from rice (Oryza sativa L. cv. Nipponbare) seedlings treated with a mixture of 2,4-dichlorophenoxyacetic acid (2,4-D), chlorotoluron, phenobarbital, salicylic acid, and naphthalic anhydride (each 100 μM). We also isolated the gene’s promoter region. Endogenous CYP72A21 expression in rice seedlings treated with 2,4-D, herbicides esprocarb, or trifluralin was increased in the aerial part of seedlings. An expression plasmid, pI21pg, containing the GUS gene under the control of the CYP72A21 promoter was introduced into rice plants. GUS was expressed constitutively in roots, but this expression was suppressed by 2,4-D treatment. 2,4-D and other auxins induced GUS expression effectively in the stem and leaves. Histological observation revealed that GUS was expressed mainly in the base of the stem. Treatment with the herbicides acetochlor, esprocarb, and propyzamide induced GUS expression in the aerial parts of the seedlings. The CYP72A21 promoter was highly responsive to treatments with various chemicals, and thus might be useful for producing transgenic plants for biomonitoring of environmental chemicals.     

一株乙草胺降解菌的分离及其降解特性研究

【目的】分离获得一株能有效降解乙草胺的菌株,并研究其降解乙草胺的影响因素,为乙草胺生物修复提供微生物资源。【方法】通过富集培养和分离培养,从样品中筛选能以乙草胺为唯一碳氮源的菌株。通过划线培养获得单菌落,并采用革兰氏染色法和16S r RNA基因测序进行菌株的初步鉴定和系统分类。通过单因素试验研究初始乙草胺浓度、外加碳氮源对其降解乙草胺的影响,并基于正交设计进行优化。【结果】分离获得的一株菌为革兰氏阴性菌,初步确定为Pseudomonas sp.,能有效利用乙草胺进行生长。单因素试验证明在乙草胺初始浓度为10 mg/L时降解率最高;外加碳氮源能提高乙草胺降解率,其中葡萄糖和蛋白胨分别最为有效。正交设计表明在最优条件下,其对乙草胺降解率可以达到80.2%。【结论】菌株A-1能有效利用乙草胺进行生长,其降解乙草胺受多种因素影响。本研究将为利用进行该菌株进行乙草胺污染修复提供菌种资源。     

甲胺磷和铜对黑土中乙草胺的蚯蚓生态解毒过程的影响

采用微宇宙培养法,通过蚯蚓对比试验,研究了甲胺磷和Cu分别与乙草胺共存条件下黑土中乙草胺降解过程的动态变化,探讨利用蚯蚓强化乙草胺解毒过程的可行性.结果表明,无论是否加入蚯蚓,在乙草胺单一污染的土壤中乙草胺的降解符合一级反应动力学规律;蚯蚓活动促进了乙草胺的降解解毒过程;土壤中甲胺磷或Cu分别与乙草胺共存时,对乙草胺的降解有抑制效应;甲胺磷与乙草胺复合及Cu与较高浓度乙草胺复合时,改变了乙草胺随时间的降解变化规律; 而Cu与较低浓度乙草胺复合时,对其降解解毒过程无明显影响.     

乙草胺和甲胺磷对农田黑土可培养真菌数量及种群结构的影响

应用传统及PCR-DGGE方法(denaturing gradient gel electrophoresis),分别对不同浓度乙草胺、甲胺磷胁迫下黑土中可培养真菌CFU(colony forming units)、种群丰富度(richness)及种群结构动态变化规律进行了研究.结果表明,在实验室微域条件下,乙草胺对黑土可培养真菌CFU的影响随处理浓度的增加而抑制作用增强,表现出由低浓度(50 mg·kg^-1)时的刺激生长到高浓度(250 mg·kg^-1)时的长期抑制效应;250 mg·kg^-1甲胺磷在8周处理过程中对土壤可培养真菌生长具有显著的刺激效应,使可培养真菌CFU比对照增加10倍,但50和150 mg·kg^-1甲胺磷处理对土壤可培养真菌CFU无显著影响.种群丰富度系数分析结果表明,高、中浓度乙草胺处理可使土壤可培养真菌种群丰富度不可逆地降低.土壤真菌rDNA特异PCR-DGGE聚类分析结果表明,不同浓度乙草胺、甲胺磷处理均不同程度地对土壤可培养真菌的种群组成和结构造成影响,其中甲胺磷尤为显著.     

甲胺磷、乙草胺和铜单一与复合污染对蚯蚓的毒性效应研究

以赤子爱胜蚓(Eisenia foetida)为例,通过滤纸急性毒性试验法研究了东北黑土区普遍存在的3种农用化学品甲胺磷、乙草胺和Cu对蚯蚓的单一与复合毒性效应．单一实验结果表明,三者对蚯蚓均有毒性,它们的毒性顺序为乙草胺＞甲胺磷＞Cu,半致死浓度分别为：0．307、0．708和118．70mg.kg^-1;同时通过观察可知,乙草胺与Cu以皮肤渗入蚯蚓体的毒性效应较甲胺磷明显．复合毒性实验结果表明,低浓度Cu与高浓度Cu对甲胺磷的毒性均有增强作用;低浓度Cu对乙草胺的毒性有削弱作用,但高浓度Cu对乙草胺的毒性有增强作用．可见,三者对土壤生态系统生态安全性和土壤健康质量存在潜在危害,同时这几种污染物的共存进一步加大了潜在危害性,且复合毒性效应与各组浓度组合密切相关．