Bioavailability of bound residue derived from ^(14)C-labeled chlorsulfuron in soil and its mechanism of phytotoxicity

The bioavailability of bound residue(BR) derived from 14 C-labeled chlorsulfuron in soil and effect of the main components of the BR on growth of rape(brassica napus) and rice(Oryza sativa L.) were investigated. The results showed that the BR with the concentration of 0 28 and 0 56 nmol/g air-dried soil, which was calculated by special radioactivity of 14 C-labeled chlorsulfuron parent compound, resulted in significant depression effect on growth of rape seedling. It was assured that the main components(2-amino-4-methoxyl-6-methyl-1,3,5-triazine, 2-amino-4-hydroxyl-6-methyl-1,3,5-triazine, and 2-chloro-benzenesul-f onamide) of the BR did not inhibit the growth of rape and rice. LC-MS analysis demonstrated that the parent compound previously bound to the soil matrix could be again released and transformed into methanol-extractable residue during the course of rape growth. It was concluded that the molecular leading to the phytotoxicity to rape and rice in the BR is still the parent compound.

Identification of the bound residue composition derived from ^(14)C-labeled chlorsulfuron in soil by using LC-MS and isotope tracing method

A new method for extracting the bound residue(BR) derived from 14 C-labeled chlorsulfuron in soils was developed, and the technique of combining LC-MS with isotope tracing method was subsequently applied to identify the composition of the 14 C-BR in a loamy Fluvent derived from marine deposit. The results showed that the 14 C-[2-amino-4-methoxyl-6-methyl-1,3,5]-triazine, 14 C-[2-amino-4-hydroxyl-6-methyl-1,3,5]-triazine and 14 C-chlorsulfuron parent compound constituted the main composition of the 14 C-BR derived from 14 C-labeled chlorsulfuron in the soil. The radioactive ratio of three compounds accounted for 39.8%, 35.4% and 17.9% of total recovered radioactivity, respectively. However, a small amount(3.6% of total recovered radioactivity) of the complex of 14 C-[2-amino-4-hydroxyl-6-methyl-1,3,5]-triazine might have existed in the 14 C-BR in association with an unknown soil substrate. 2-chlorobenzenesulfonamide was also detected to be one of the components of the BR. The results could well explain the mechanism of phytotoxicity caused by the BR derived from chlorsulfuron in soil. In addition, the mechanism of BR formation in soil was also discussed in details.

Influence of chlorsulfuron herbicide on size of microbial biomass in the soil

A laboratory incubation experiment was conducted to study the effect of chlorsulfuron herbicide on the size of the microbial in loamy sand soil. The herbicide was applied, at four levels that were control, field rate 0\^01 (FR), 0\^1 (10FR) and 1 (100FR) μg/g. Determinations of microbial biomass C content and microbial biomass N content were carried out 1, 3, 5, 7, 10, 15, 25 and 45 days after herbicide application. In comparison to untreated soil, the microbial biomass carbon and biomass nitrogen decreased significantly in soil treated with herbicide in levels 10FR and 100FR within the first 10 days incubation. A more considerable increase in the microbial biomass C∶N ratio was observed in the herbicide treated soil than the non treated control. This effect was transitory and only at the higher rates of chlorsulfuron was significant.

Dynamic response of chlorsulfuron herbicide to nitrogen mineralization and the ratio of microbial biomass nitrogen to nitrogen mineralization in the soil

A laboratory incubation experiment was conducted to elucidate the effect of chlorsulfuron herbicide on nitrogen mineralization and the ratio of microbial biomass nitrogen to nitrogen mineralization (N mic /N min ratio) in loamy sand soil.The herbicide was applied at four levels that were control, field rate 0\^01 (FR), 10 times of field rate 0\^1(10FR),and 100 times of field rate 1\^0 (100FR) μg/g soil. Determinations of N\|mineralization and microbial biomass\|N content were carried out 1,3,5,7,10,15,25 and 45 days after herbicide application. In comparison to untreated soil, the N\|mineralization decreased significantly in soil treated with herbicide at levels 10FR and 100FR within the first 5 days incubation. A more considerable reduction in the N mic /N min ratio was observed in the herbicide treated soil than the non\|treated control.Among the different treatment of chlorsulfuron, 100FR displayed the greatest biocidal effect followed by 10FR and FR,showing their relative toxicity in the order of 100FR>100FR>FR.The results indicated that the side effect of this herbicide on N\|mineralization is probably of little ecological significance.

Evaluation on the Joint Action Between Chlorsulfuron and Haloxyfop-R by Bioassay

The joint action between chlorsulfuron and haloxyfop R was evaluated by bioassay with wheat and corn,respectivly.The dose response curve derived from wheat bioassay showed that the inhibition of haloxyfop R to wheat root growth wasn't affected by the increasing rate of chlorsulfuron.It indicated that chlorsulfuron had no antagonism to haloxyfop R.Meanwhile,the variation analysis of corn bioassay indicated that these two herbicides had joint action on inhibition to corn primary root growth.The joint action was evaluated as additive action by using Isobole Method.So chlorsulfuron and haloxyfop R could be used as tank mixture.

Electrochemical Degradation of Chlorsulfuron Herbicide from Water Solution Using Ti/IrO₂-Pt Anode

Chlorsulfuron (ChS) which is a nonbiodegradable herbicide was effectively removed using an electrochemical method at the Ti/IrO2-Pt anode. The influences of current density, initial ChS concentration, initial solution pH and different NaCl dosages on electrochemical degradation of ChS were investigated. HOCl formed during electrolysis and quickly generated .OH radicals would likely play an important role in the electrochemical degradation of ChS with the presence of NaCl. At current density of 20 mA?cm–2, ChS concentration decreased from 1 mg.L–1 to 0 mg.L–1 after 10 min electrolysis with 0.2 g?L–1 NaCl dosage. It was found that the ChS removal rate increased with increasing current density and the ChS degradation was similar at different initial pH values, which means that Ti/IrO2-Pt anode can be used in a wide pH range. The electrochemical performance of Ti/IrO2-Pt anode for degradation of ChS will not decrease after serviced for a long time. These results reveal that an electrochemical approach would be a novel treatment method for effective and rapid degradation of ChS herbicide from aqueous solution.

Determination of Herbicide Chlorsulfuron Residual Kinbetic and Accumulated Residues in Soil by Gas Chromatography

In this paper, residual kinetic and accumulated residues of chlorsulfuron in soil was studied by Gas chromatograhy. The result identify, chlorsulfuron was applied to winter wheat at rates of 15 g aiha -1 ; 30 g ai·ha -1 , degradation on of Half-life in soil were 43.2 days; 36.9 days, respectively, and one year later, the residues in soil were 0.34 ng·g -1 ; 0.43 ng·g -1 , respectively. Chlorsulfuron was applied continuously several years, the residues in soil was accumulated.

Distribution of ^(14)C-chlorsulfuron bound residues in soil organic matter

The reason why chlorsulfuron(2-chloro-N-[4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino]carbonyl]benzenesulfonamide)bound residues can still make an in-jury to rotational crops is still kept unknown. The experiment was conducted under laboratory conditions to determine the dynamics of extractable and non-extractable (bound) residues of chlorsulfuron in soil, and the distribution of chlorsulfuron bound residues in organic matter fractions. The results showed that extractable 14C-residues decreased t0 25.12% of applied chlorsulfuron over an incubation period of 150 days;this in turn, the formation of bound residues increased to 47.07% of the applied. The proportions of 14C-bound residues in soil organic matter fractions increase in order of: humic acid (HA)<humin<fulvic acid(FA), most of bound residues ekisted in FA fraction, however, the amount of bound residues in humin fraction increase with incubation time. The fact that most of bound residues existed in water-soluble FA fraction is tentatively regarded as one of major reasons why 14C-chlorsulfuron bound residues can still make an injury to rotational crops.

The release of ^(14)C-chlorsulfuron bound residue by autoclaving method and its identification

When individual microorganisms were used to release bound pesticide residues, it was ussually not take into full account whether the autoclavingmethod could lead to the release of bound residues. The soil containing bound 14Cchlorsulfuron residues was treated with an autoclave in this study. The results revealthat the bound 14C-chlorsulfuron residue can be released from the soil when treatedwith the autoclave and the release rate can be remarkably enhanced by adding water into the soil when subjected to such treatment. A TLC analysis showed that thereleased 14C-residue was one of the degraded products of 14C-chlorsulfuron. Afterderivatization and analysis using the GC-MS, the released 14C-residue was tentativelyidentified aS 2-amino-4-hydroXyl-6-methyl-1,3,

Research on controllable alkaline soil degradation of 5-substituted chlorsulfuron

Sulfonylurea（SU） has become one class of the most important herbicides worldwide due to their ultralow application rate and mammalian toxicity. Recently application licenses of 3 classical SU herbicides chlorsulfuron, metsulfuron-methyl and ethametsulfuron were suspended due to their undesirable long persistence which is incompatible with the particular rotation planting system in China. Our previous study has discovered that electron-donating groups, especially dimethylamino and diethylamino substituents, on the 5 th position of the benzene ring in chlorsulfuron, greatly accelerated its degradation rate in an acidic soil（p H 5.41）. Owing to the natural slower degradation of SUs in alkaline soil,dimethylamino and diethylamino substituted chlorsulfuron Ia and Ib were further studied in an alkaline soil（p H 8.46） with chlorsulfuron as a control. The experimental data indicated that the half-life of degradation（DT50） of Ia was 3.36 days while Ib was 6.25 days which amounted to 30 and 15 folds faster than chlorsulfuron（DT5084.53 days）, respectively. The research confirmed that our newly-designed structures Ia and Ib can hasten their degradation rate in alkaline soil as well as in acidic soil. This structural modification of the classical SU provided an opportunity to control the degradation rate to reduce their impact on relevant environment and ecology.

Molecular Drug Resistance Prediction for Acetohydroxyacid Synthase Mutants Against Chlorsulfuron Using MB-QSAR

Chlorsulfuron is the first commercialized sulfonylurea herbicide, which targets acetohydroxyacid synthase （AHAS）. Mutations in AHAS have caused serious herbicide resistance to chlorsulfuron. Quantitative description of the herbicide resistance in molecular level will benefit the understanding of the resistance mechanism and aid the design of resistance-evading herbicide. We have recently established a MB-QSAR （Mutation-dependent Biomac- romolecular Quantitative Structure-Activity Relationship） method to conduct the 3D-QSAR study in biomacro- molecules. Herein, based on the herbicide resistance data measured for a series of AHAS mutants against chlorsul- furon, we constructed MB-QSAR models to quantitatively predict the herbicide resistance and interpret the struc- ture resistance relationships for AHAS mutants against chlorsulfuron. Quite well correlations between the experi- mental and the predicted pKi values were achieved for MB-QSAR/CoMFA （q^2=0.705, r^2=0.918, r^2pred=0.635） and MB-QSAR/CoMSIA （q^2=0.558, r^2=0.940, r^2pred=0.527） models, and interpretation of the MB-QSAR models gave chemical intuitive information to guide the resistance-evading herbicide design.

石防风原生质体遗传转化及抗除草剂植株的再生

以石防风（Ｐｅｕｃｅｄａｎｕｍｔｅｒｅｂｉｎｔｈａｃｅｕｍ（Ｆｉｓｃｈ．）Ｆｉｓｃｈ．ｅｘＴｕｒｃｚ．）叶柄愈伤组织为材料建立以致密细胞团为主的悬浮培养物，用酶解法获得原生质体。用ＰＥＧ法将拟南芥菜（Ａｒａｂｉｄｏｐｓｉｓｔｈａｌｉａｎａ（Ｌ．）Ｈｅｙｎｈ．）抗除草剂基因导入原生质体后进行液体浅层培养。转化细胞经除草剂ｃｈｌｏｒｓｕｌｆｕｒｏｎ筛选，通过胚状体途径产生抗性小植株。转化处理１０６个原生质体，以加入４０～５０μｇ／ｍＬ质粒ＤＮＡ，ＰＥＧ终浓度为１０％，于１ｍＬ转化介质中，２６℃黑暗下处理２０ｍｉｎ的效果最好。ｃｔＤＮＡ的加入对转化结果无明显影响。分子杂交试验表明，突变的ａｌｓ基因已整合进转化植株的基因组中。转基因植株的细胞在脱分化过程中仍具有抗ｃｈｌｏｒｓｕｌｆｕｒｏｎ的能力；移栽成活的转基因小苗仍表现出抗除草剂特性，而未转化的植株在低浓度除草剂下即逐渐死亡。表明转入的ａｌｓ基因在石防风细胞内能够稳定表达。

氯磺隆和苯磺隆对玉米乙酰乳酸合成酶抑制作用的研究

用玉米沙培主根长度法测定了玉米品种农大 3138和农大 10 8对氯磺隆和苯磺隆的相对敏感性。结果表明 ,农大 3138耐药能力比农大 10 8强 ,氯磺隆对玉米生长的影响比苯磺隆大。有关玉米离体乙酰乳酸合成酶(ALS)的研究结果表明 ,氯磺隆和苯磺隆对两种玉米离体ALS酶具有强烈的抑制作用 ,是玉米ALS酶的非竞争性抑制剂 ,氯磺隆对两种玉米ALS酶的抑制作用强于苯磺隆。低浓度的氯磺隆和苯磺隆对活体ALS酶无抑制作用 ,高浓度下才抑制活体ALS酶的活性。

麦谷宁生测方法及其对玉米的安全性研究

选用种植面积较大且抗逆性较强的玉米品种农大 10 8为指示植物 ,研究了麦谷宁的玉米沙培试验方法。结果表明 ,浸种催芽 ,播种后先盖覆沙量的一半后加药 6 0 m L,再盖沙至 2 cm厚 ,于 2 5℃黑暗培养 3d,可获得满意的结果。回归分析表明 ,麦谷宁浓度的对数与玉米主根长抑制率相对应的机率值成很好的线性关系 ,r2 均大于 0 .90。就大面积种植的 16个玉米品种对麦谷宁的敏感性测定结果表明 ,掖单 12对麦谷宁较敏感 ,农大 3138对麦谷宁耐药力最强 ,各品种对麦谷宁的 IC50 值均大于 7.38μg· kg-1。

一株绿磺隆降解菌的分离鉴定及其特性研究

从长期施用绿磺隆的土壤中采取土样 ,经驯化富集后筛选到一株能高效降解绿磺隆的细菌LHL 1菌株 ,经初步鉴定为黄单胞菌 (Xanthomonassp)。在此基础上 ,研究了该菌株对绿磺隆的降解特性。结果表明 :在绿磺隆浓度为 2 0mgL- 1的无机盐培养基中 ,3 0℃、1 5 0rmin- 1振摇 40h ,其对绿磺隆的降解率达 62 %。在所试的金属离子中 ,Pb2 +、Ag+抑制其生长 ,Ba2 +、Al3+、Zn2

绿黄隆在三种土壤中的降解

在实验室内，采用改进的玉米根长生测方法，定期测定一定温、湿度条件下绿黄隆在３种土壤中的残留动态。对降解时间和残留剂量进行回归分析，符合一级反应动力学指数方程Ｃ＝Ｃ０ｅ－ｋｔ，相关系数达极显著水平，半衰期ｔ１／２＝ｌｎ２／ｋ。实验结果表明，在２５℃、２５％温、湿度条件下，绿黄隆在太湖水稻土中降解最快，半衰期为１．６周；其次是砂姜黑土，半衰期为２．５周；高砂土中降解最慢，半衰期为１３．３周。分析认为，土壤ｐＨ值和微生物量是影响绿黄隆降解的主要因素。高温灭菌土壤测得绿黄隆在砂姜黑土的灭菌土和未灭菌土中，半衰期分别为２６．５周和２．１周；太湖水稻土的灭菌和未灭菌土中，半衰期分别为５．０周和０．９周。从而进一步证实，绿黄隆在太湖水稻土中以非酶水解和微生物活动共同降解，在碱性砂姜黑土中主要以微生物降解。探讨了绿黄隆在３种土壤中的残留动态对农业生产的重要性，建议长江流域碱性沙质土壤农区慎用或禁用绿黄隆。

农作物对磺酰脲类除草剂耐性的研究

不同作物品种对磺酰脲类除草剂的耐性有一定差异。春小麦不同品种对绿磺隆的耐性差异很小，但在不同温度条件下有一定差异。大豆品种问对立磺隆耐性不同，荆山朴、东农７７－８０４，哈３７－６４３７和７９０２的耐性最强，绿秣食豆、东农３９和龙６８０４耐性中等，合丰２５，礼炮２１６和东农３３耐性较差。玉米不同类型对玉农乐耐性不同，其耐性顺序为硬粒型＞一般型＞普甜型＞爆裂型。

氯磺隆的化学行为

氯磺隆是典型的乙酰乳酸合成酶抑制剂 ,在酸性条件下主要以中性分子形式存在 ,其水解反应是准一级的SN2 反应 ;在中性或碱性条件下 ,主要以阴离子形式存在 ,水解反应较慢 .在土壤中 ,除化学降解外 ,微生物降解也是氯磺隆另一重要环境归趋 ,而光化学降解并非氯磺隆环境归趋的主要方式 .

安全剂R-28725保护玉米免受氯磺隆药害的作用

采用生物测定法研究了安全剂R-28725保护玉米免受除草剂氯磺隆药害的作用。在氯磺隆毒土浓度为2μg/kg时,使用5mg/kg R-28725浸种处理,玉米根部受到氯磺隆抑制的谷胱甘肽(GSH)含量由空白对照的57.3%恢复至83.4%;玉米叶片中乙酰乳酸合成酶(ALS)活性增加了17.2%;玉米根部的谷胱甘肽-S-转移酶(GST)活性增加了191.8%;GST酶促反应动力学参数Vmax增大102.5%,Km减小40.0%。结果显示:R-28725能够提高氯磺隆处理后玉米中GSH的含量,增加GST和ALS活性,增强了玉米根部GST酶对底物的亲和力,缓解氯磺隆对玉米产生的药害。

日本看麦娘对氯磺隆、异丙隆和骠马的抗药性

在连续施用氯磺隆不同年限的麦田采集日本看麦娘种子.室内进行不同剂量的氯磺隆、异丙隆、骠马处理,测定日本看麦娘植株鲜重抑制率.连续施用氯磺隆5～6年后再施用异氯混剂(异丙隆与氯磺隆的混配剂)3～5年,日本看麦娘的抗性指数达325.80～613.40;麦田连续施用氯甲混剂(氯磺隆与甲磺隆的混配剂)3～4年、异氯混剂2～3年,日本看麦娘的抗性指数为15.22～42.45;对氯磺隆产生抗性的日本看麦娘种群(R1～R9)均对异丙隆、骠马敏感;连续施用骠马2～3年麦田的日本看麦娘种群对骠马未产生抗性.