扑草净对枣树生理生化影响的研究

本文主要研究了扑草净对枣树新梢生长量、叶片中叶绿素含量、丙二醛含量以及膜相对透性的影响。结果表明:扑草净短期内对枣树的生长产生了比较明显的影响,且浓度越大影响越大,但20d后各浓度对枣树的影响都几乎消失。在枣树圃地或枣树与农田间(混)作地进行化学药剂除草时,扑草净浓度在2g/kg以下均可安全使用。     

二甲戊灵、扑草净与丙炔氟草胺的配比筛选及在油莎豆田的应用效果

为探索和论证二甲戊灵、扑草净与丙炔氟草胺三者复配的合理性及三者复配制剂对油莎豆Cyperus esculentus var. sativus田杂草的防效和对油莎豆的安全性,本试验依据除草剂室内活性测定标准并借鉴除草剂防治大豆田杂草田间药效试验准则,进行了一系列试验。结果表明,二甲戊灵、扑草净与丙炔氟草胺三者联合作用对稗草Echinochloa crus-galli、苘麻Abutilon theophrasti、藜Chenopodium album 3种杂草表现为相加或增效作用,当三者混配比例为30∶30∶1时联合作用为增效,为最佳比例。此比例下的36.6%二甲戊·扑·丙炔SC对油莎豆田一年生杂草有较好的防效,试验有效剂量在1 647.0~1 921.0 g/hm2范围内,对油莎豆出苗、生长较安全;施药后40 d对一年生杂草的防效为91.3%~97.7%。由此可见,二甲戊灵、扑草净与丙炔氟草胺三者联合研制新药剂具有可行性,能扩大杀草谱和应用范围,可用于油莎豆田杂草防控,适宜用量1 647.0~1 921.0 g/hm2。     

Rapid mineralisation of the herbicide isoproturon in soil from a previously treated Danish agricultural field

Mineralisation of the phenylurea herbicide isoproturon (3-(4-isopropylphenyl)-1,1-dimethylurea) and two of its known metabolites, 3-(4-isopropylphenyl)-1-methylurea (monodesmethyl-isoproturon) and 4-isopropylaniline, was studied in Danish agricultural soils with or without previous exposure to isoproturon. A potential for rapid mineralisation of isoproturon and the two metabolites was present in soils sampled from three plots within an agricultural field previously treated regularly with the herbicide, with 34-45%, 51-58% and 33-36% of the added [phenyl-U-14C]isoproturon, [phenyl-U-14C]monodesmethyl-isoproturon and [phenyl-U-14C]4-isopropylaniline metabolised to [14C]carbon dioxide within 30 days at 20 degrees C. In contrast, such extensive mineralisation of these three compounds was not observed within this period in soils sampled from two other agricultural fields without previous treatment with isoproturon. The mineralisation patterns indicated growth-linked metabolism of the three compounds in the previously exposed soils, and doubling times for [14C]carbon dioxide production ranged from 1.6 to 3.2, 1.0 to 2.1 and 1.3 to 1.7 days for isoproturon, monodesmethyl-isoproturon and 4-isopropylaniline, respectively. The ability to mineralise [phenyl-U-14C]isoproturon to [14C]carbon dioxide was successfully sub-cultured to a fresh mineral medium which provided isoproturon as sole source of carbon and nitrogen. One of the soils sampled from an agricultural field not previously treated with isoproturon showed accelerated mineralisation of [phenyl-U-14C]4-isopropylaniline toward the end of the experiment, with a doubling time for [14C]carbon dioxide production of 7.4days. This study indicates that the occurrence of rapid mineralisation of the phenyl ring of isoproturon to carbon dioxide is related to previous exposure to the herbicide, which suggests that microbial adaptation upon repeated isoproturon use may occur within agricultural fields.     

The impact of altered herbicide residues in transgenic herbicide-resistant crops on standard setting for herbicide residues

The global area covered with transgenic (genetically modified) crops has rapidly increased since their introduction in the mid-1990s. Most of these crops have been rendered herbicide resistant, for which it can be envisaged that the modification has an impact on the profile and level of herbicide residues within these crops. In this article, the four main categories of herbicide resistance, including resistance to acetolactate-synthase inhibitors, bromoxynil, glufosinate and glyphosate, are reviewed. The topics considered are the molecular mechanism underlying the herbicide resistance, the nature and levels of the residues formed and their impact on the residue definition and maximum residue limits (MRLs) defined by the Codex Alimentarius Commission and national authorities. No general conclusions can be drawn concerning the nature and level of residues, which has to be done on a case-by-case basis. International residue definitions and MRLs are still lacking for some herbicide-crop combinations, and harmonisation is therefore recommended.     

The cyclization transformation of the sulfonylurea herbicide flupyrsulfuron in the soil of winter wheat crops

The synthesis of 1-(4,6-dimethoxypyrimidine-2-yl)-7-trifluoromethyl-1,2,3,4-tetrahydropyrido [2,3-d]pyrimidin-2,4-dione has been carried out in such a way that the dimethoxypyrimidine substituent was unambiguously in position 1 of the pyrido[2,3-d]pyrimidine ring. This regioisomer was obtained by cyclization with phosgene of 2-(4,6-dimethoxypyrimidin-2-ylamino)-6-trifluoromethylnicotinamide which had previously been ionized with sodium hydride. It was shown to be identical to the metabolite generated in the soil of winter wheat crops treated previously with the sulfonylurea herbicide flupyrsulfuronmethyl [(methyl 2-(4,6-dimethoxypyrimidin-2-ylcarbamoylsulfamoyl)-6-trifluoromethylnicotinate]. The position of the dimethoxypyrimidine substituent had not previously been assigned unambiguously to positions 1 or 3 of the pyrido[2,3-d]pyrimidine ring. The regioisomer was also identical to the cyclization compound generated chemically from flupyrsulfuron in a sterile water buffer at pH 9. The metabolism pathways of flupyrsulfuron in soil are discussed in the light these structure determinations and compared with the soil metabolism pathways frequently observed with other sulfonylurea herbicides.     

生物炭对土壤理化性质和玉米生长的影响

以玉米品种'利禾1号'为试验材料,设计6个施肥处理,分别为空白对照(CK,不施肥);常规施肥处理(T1,N:P2O5:K2O=27:12:6);在常规施肥处理基础上减氮20％并分别增施生物炭,生物炭施用量分别为2.25(T2)、4.50(T3)、6.75(T4)、9.00 t·hm-2(T5),研究生物质炭基施对宁夏扬...     

Fitness effects of the triazine resistance mutation in Amaranthus hybridus: relative fitness in maize and soyabean crops

Fitness costs of the triazine resistance mutation were estimated in experimental populations of Amaranthus hybridus L. from Maryland and Virginia (USA). Estimated costs were attributed directly to effects of the resistance mutation, through comparisons of lines bearing similar nuclear genomes, but either resistant or susceptible cytoplasm. Experimental weed plants were established from seed in the field at a wide range of A. hybridus and crop (maize or soyabean) densities, and experiments were repeated over 3 years. Resistant cytoplasm caused large reductions in several components of fitness, but substantial differences were observed among years in these fitness costs of resistance. For the fitness component of total biomass above-ground biomass production, relative fitnesses of resistant genotypes (resistant/susceptible ratios) ranged between 0.42 and 0.70. Costs of resistance were similar in weeds growing with either maize or soyabean crops. Certain costs of resistance differed between populations: impairment of seedling establishment and early growth by the resistance mutation was evident in the Virginia population, but not in the Maryland population. This functional difference between populations was associated with greater costs of resistance in the Virginia population with respect to mid-season leaf number and total above-ground biomass production; however, only the former population difference in fitness cost was statistically significant.     

Mineralisation of the herbicide linuron by Variovorax sp. strain RA8 isolated from Japanese river sediment using an ecosystem model (microcosm)

BACKGROUND: Linuron is a globally used phenylurea herbicide, and a large number of studies have been made on the microbial degradation of the herbicide. However, to date, the few bacteria able individually to mineralise linuron have been isolated only from European agricultural soils. An attempt was made to isolate linuron‐mineralising bacteria from Japanese river sediment using a uniquely designed river ecosystem model (microcosm) treated with ¹⁴C‐ring‐labelled linuron (approximately 1 mg L^?1). RESULTS: A linuron‐mineralising bacterium that inhabits river sediment was successfully isolated. The isolate belongs to the genera Variovorax and was designated as strain RA8. Strain RA8 gradually used linuron in basal salt medium (5.2 mg L^?1) with slight growth. In 15 days, approximately 25% of ¹⁴C‐linuron was mineralised to ¹⁴CO₂, with 3,4‐dichloroaniline as an intermediate. Conversely, in 100‐fold diluted R2A broth, strain RA8 rapidly mineralised ¹⁴C‐linuron (5.5 mg L^?1) and more than 70% of the applied radioactivity was released as ¹⁴CO₂ within 3 days, and a trace amount of 3,4‐dichloroaniline was detected. Additionally, the isolate also degraded monolinuron, metobromuron and chlorobromuron, but not diuron, monuron or isoproturon. CONCLUSION: Although strain RA8 can grow on linuron, some elements in the R2A broth seemed significantly to stimulate its growth and ability to degrade. The isolate strictly recognised the structural difference between N‐methoxy‐N‐methyl and N,N‐dimethyl substitution of various phenylurea herbicides. Copyright © 2010 Society of Chemical Industry     

Effects of calcium on permethrin-phosphatidylserine interactions in model membranes

The effects of permethrin on lipid packing order in liposomal membranes containing phosphatidylserine (PS) have been examined in the presence and absence of calcium. Steady-state fluorescence anisotropy and phase-modulation techniques were utilized with the fluorescent probes 1,6-diphenyl-1,3,5-hexatriene (DPH), trans-parinaric acid, and cis-parinaric acid to determine alterations in lipid packing by permethrin as a function of temperature. In general, permethrin exhibited disordering effects only in gel phase lipid. In pure PS membranes, permethrin had little effect on small unilamellar vesicles (SUVs). However, substantial reductions in lipid packing order were detected by decreases in DPH fluorescence anisotropy when these SUVs underwent isothermal fluid to gel phase transition upon exposure to Ca²⁺. Although Ca²⁺ increased the main PS phase transition temperature (T_c), a small residual phase transition was detectable by parinaric acid anisotropy and lifetimes within the temperature range corresponding to the SUV phase transition. Permethrin smoothed this residual transition, suggesting that this compound altered a process which was preventing a portion of PS from undergoing the Ca²⁺-mediated isothermal transition to the solid phase. In mixed liposomes containing dipalmitoyl phosphatidylcholine (DPPC) at a PS:DPPC ratio of 3:2, the T_c of the SUVs was increased while that of the Ca²⁺-treated vesicles was decreased. As in the pure PS system, permethrin had a greater disordering effect upon the lipid packing in the Ca²⁺-treated membranes. There was a slight disordering effect by permethrin in PS:DPPC SUVs at temperatures below the T_c, indicating the existence of DPPC enriched domains in the gel phase lipid which were sensitive to permethrin. The results demonstrate that Ca²⁺-mediated changes in membrane characteristics, such as isothermal fluid to gel phase transition, can influence membrane sensitivity to the lipid disordering effects of permethrin.     

农田耕种对土壤酶活性及土壤理化性质的影响

通过分析连续耕种5、10、15、20、30年农田土壤的4种酶活性及土壤理化性质,得出结论：随着种植年限的增加,灌溉、耕作、施肥等人类生产活动改变了酶在各土层间的活性格局。过氧化氢酶活性和蔗糖酶活性随年限的增加总体趋势增加,有机质和土壤水分变化类似,一致表现出＂N＂形的变化趋势,脲酶活性和磷酸酶活性呈现＂M＂形的相似变化...     

不同旱作节水灌溉条件对土壤理化性质及水稻产量的影响

为探索更为适合的水稻节水灌溉方式,于2017—2019年在宁夏暖泉农场开展大田试验,采用三因素对比设计,设置3种不同水稻节水灌溉方式(保墒旱直播MDDS、播后上水旱直播IDFS及覆膜滴灌旱作FMDI),研究了不同节水灌溉方式对水稻土壤理化性质及产量的影响。结果表明：FMDI分蘖期0～10 cm土层日平均地温3 a平均较IDFS和MDDS增加1.7℃(P<0.05);FMDI节水效果明显,在灌溉水平为80%田间持水量条件下,依然可以保持较高的土壤含水量(3年分别为20.1%、19.9%及20.3%);MDDS和IDFS土壤紧实度分别比FMDI平均高出1.74倍、1.77倍;FMDI处理连续3 a土壤有机质、全氮、全磷和全钾较其他2种耕作处理均有显著增加;FMDI处理有显著增产作用,其3 a经济产量和收获指数均最高,与MDDS相比,FMDI的水分利用效率3个年份增幅分别为54.0%、60.0%和56.0%。综上可知,覆膜滴灌旱作(FMDI)方式为适宜该地区水稻种植的蓄水保墒、增温稳温、培肥地力和高产高效的土壤耕作覆盖措施。     

Effects of DDT on electrical properties of lecithin-decane bilayer membranes

Lecithin-decane bilayer membranes were treated with DDT and valinomycin, either by adding the compounds to the electrolyte around the membrane or by adding them directly to the lecithin-decane. Membrane capacitance was calculated using the dc transient technique. Specific capacitance was determined from capacitance versus area regressions and was not significantly altered by DDT. Specific K⁺ conductance was decreased by DDT, but only when DDT and the K⁺ carrier, valinomycin, were administered to the electrolyte where they may have interacted hydrophobically. It is concluded that the valinomycin-induced conductance of artificial membranes is inappropriate as a model for investigating the effects of DDT on the electrical properties of excitable membranes.     

Organoclays for controlled release of the herbicide fenuron

Organoclays were assayed as matrices in which to associate herbicides, with the aim of decreasing product losses that could give rise to water contamination from agricultural activities. Fenuron was selected as model of a very mobile and highly water-soluble herbicide. Two different organoclays of high (A-HDT) and low (H-C18) reversible fenuron sorption were selected. Herbicide-organoclay complexes were prepared from the two organoclays and with two different fenuron contents (20 and 40 g AI kg-1) and two different mixing times, so as to form a series of weak and strong complexes. The release of fenuron from those complexes into water and water/soil suspensions gave values of T50 (time to release 50% of the fenuron content) ranging from 0.3 min to 2400 h. The total fenuron released in these closed systems ranged from 48 to 80% of the fenuron in the complex. The organoclay type (high or low sorptivity) had the greatest influence on fenuron release, followed by the strong or weak complex, suggesting that herbicide-organoclay interactions are the main factors controlling release. Soil column leaching experiments showed fenuron-organoclay complexes to be effective in reducing the peak herbicide concentration in the leachate to a half (6 microns) or a quarter (3 microns) of that obtained from the free technical compound (12 microns). Herbicide lost through leaching was reduced from 78% for the free technical fenuron to 50-30%, depending on the organoclay used as carrier and the strength of the complex. Bioassay with ryegrass showed that the weak fenuron/H-C18 complex (40 g AI kg-1) gave the same herbicidal activity as technical fenuron. The potential suitability of low-sorptive organoclays for conferring slow-release properties on the fenuron complex has been demonstrated.     

助剂对氯虫苯甲酰胺药液理化性质及在玉米叶片上沉积分布的影响

为选择用于植保无人机作业的喷雾助剂,利用全自动张力仪和接触角测量仪测定添加4种不同喷雾助剂后0.5%氯虫苯甲酰胺药液的表面张力及在玉米叶片上的接触角,应用大疆T20型植保无人机进行田间喷雾,分析添加4种喷雾助剂对玉米冠层不同位置雾滴密度、雾滴覆盖率和雾滴沉积量的影响。结果显示,添加迈飞和Agrospred 910喷雾助剂后,药液的表面张力分别较未添加助剂时显著降低19.6%和30.1%;不同喷雾助剂对药液在玉米叶片上接触角的影响各不相同,添加Agrospred 910助剂后液滴接触叶片60 s后接触角降至11.92°;添加4种喷雾助剂能够有效提高玉米冠层的雾滴密度、雾滴覆盖率和雾滴沉积量,其中添加Agrospred 910助剂后雾滴密度、雾滴覆盖率及雾滴沉积量分别较对照增加了36.93%、35.92%和61.90%。表明在玉米田间使用植保无人机喷雾施药时,可以优选使用Agrospred 910喷雾助剂。     

多壁碳纳米管固相萃取气相色谱-串联质谱法测定乌龙茶及土壤中10种三嗪类除草剂残留

建立了乌龙茶及土壤中10种三嗪类除草剂(西玛津、莠去津、扑灭津、特丁津、敌草净、环丙津、西草净、莠灭净、扑草净和特丁净)残留的气相色谱-串联质谱(GC-MS/MS)分析方法。样品经乙腈提取后,以多壁碳纳米管(MWCNTs)、N-丙基乙二胺(PSA)、C18、MgSO4为净化剂分散净化后,在GC-MS/MS多反应监测(MRM)模式下进行测定,空白基质匹配标准曲线外标法定量。研究了不同提取溶剂、不同吸附剂种类及用量对提取净化效率的影响。结果表明:在各自质量浓度范围内(西草净和扑草净在10~500 μg/kg,其余8种除草剂在5~500 μg/kg)具有良好线性关系,相关系数(r)均大于0.99,10种三嗪类除草剂的定量限(LOQ)为5.0~10 μg/kg。在5~100 μg/kg添加水平下,10种三嗪类除草剂在乌龙茶和土壤中的平均回收率在75%~111%之间,相对标准偏差(RSD)在3.1%~8.7%(n=6)之间。该方法操作简单、净化效果好、灵敏度高,具有良好的适用性,能够满足乌龙茶及土壤中10种三嗪类除草剂残留分析测定的要求。     

保护性耕作对黄土高原春玉米田土壤理化特性的影响

为了探索黄土高原春玉米区保护性耕作农田土壤理化特性变化,测定分析了保护性耕作处理第二年春玉米生长不同时期农田土壤容重、水分和养分变化.结果表明,保护性耕作处理在玉米生长前期0～10 cm土壤容重呈下降趋势且小于传统耕作,但后期增加幅度较大;与传统耕作相比保护性耕作能显著增加玉米生长前期表层0～60 cm和后期100～200 cm土壤含水量 ,有较好保水、蓄水作用;保护性耕作下表层0～20 cm土壤养分指标除全磷外,均表现为稳定升高趋势,且能有效提高土壤全钾和速效钾含量;土壤有机质、全氮、速效氮、速效磷含量低于传统耕作,但变异系数较小.     

Application of coupled liquid chromatography–mass spectrometry in photolysis studies of the herbicide triflusulfuron‐methyl

The photochemical fate of the herbicide triflusulfuron‐methyl in aqueous solution under UV light (λ > 290 nm) was investigated. Nine photoproducts were detected and tentatively identified by LC/MS and LC/MS/MS analysis. The main routes of degradation involve the cleavage and/or contraction of the sulfonylurea bridge with the elimination of sulfur dioxide, which increases the acidity of the reaction medium. On the basis of the results obtained a photodegradation pathway is proposed. © 2001 Society of Chemical Industry     

Adsorption of systemic fungicides and a herbicide by some components of plant tissues,in relation to some physicochemical properties of the pesticides

Lignin, an important component of plant tissues, adsorbed five systemic fungicides and one herbicide (carbendazim, triadimefon, nuarimol, triarimol, fenarimol and fluometuron) more strongly than bovine serum albumin, cellulose, ethylcellulose or sodium polygalacturonate. Significant correlations were found between the extent of the adsorption of the pesticides on the lignins extracted from three different plant species, and the log Poet (Poet is the octan-1-ol/water partition coefficient) of the compounds. The more lipophilic fungicides triarimol and fenarimol (log Poet about 2.6) were adsorbed to the greatest extent. Fluometuron, triadimefon and nuarimol (log Poet about 2.0) were moderately adsorbed, whereas carbendazim with the lowest log Poet (1.34 at pH 5.0), was adsorbed more than expected from its Poet value. The anomaly of carbendazim is discussed; it is ascribed to it's partial protonation at pH 5.0, whereas the other pesticides were non-ionised.     

Effects of the herbicide methabenzthiazuron on the physiology of wheat plants

Spring wheat (Triticum aestivum L. “Caribo”) was grown in vermiculite containing methabenzthiazuron (N-(benzothiazol-2yl)-NN′-dimethylurea) presowing. Effects of the herbicide on plant development and plant composition were analysed up to an age of 4 weeks. Inhibition of photosynthetic oxygen evolution represented the primary effect induced by the herbicidal treatment and led to a decreased concentration of soluble reducing sugars. Photosynthetic activity however recovered after 3 weeks and even increased above control values. Secondary effects following methabenzthiazuron treatment included a delayed chlorophyll breakdown, a decreased chlorophyll a/b ratio, enlarged chloroplasts, an increased concentration of soluble amino acids and of soluble protein, and an increased in vitro nitrate reductase activity. These responses are taken to indicate an increased photosynthetic and metabolic capacity in methabenzthiazuron treated wheat plants. Comparable results can be obtained with plants grown at low light intensities. It is concluded that the “physiological effects” observed in wheat plants after treatment with methabenzthiazuron are similar to a natural adaptation reaction to low light intensities. It is assumed that this adaptation reaction is caused by a low concentration of soluble reducing sugars. Experiments with plants growing at different light intensities indicated that effects due to herbicidal action were more pronounced at high light intensities. Measurements on daily fluctuations revealed a peak around noon for the sugar content and the nitrate reductase activities measured in vivo as well as in vitro. In vivo nitrate reductase activity in plants treated with 5 parts/million methabenzthiazuron was very low, presumably because of lack of sugars for the production of NADH. The protein concentration was increasing and the amino acids were decreasing during the day in herbicide treated plants, possibly indicating increased protein synthesis in the light in plants treated with methabenzthiazuron.