Spectroscopic studies on the mechanisms of adsorption of paraquat by humic acid and model compounds

Changes in the relative sizes of the carboxylic absorption bands in the infrared spectra (near 1730 and 1610 cm^?1) of adsorbents before and after treatment with paraquat (1,1′-dimethyl-4,4′-bipyridylium dichloride) showed that ion exchange is the predominant mechanism for adsorption of the bipyridyl by H⁺- ion saturated preparations of a humic acid from an organic soil, by two hydroquinone polymers and by two carboxylic ion-exchange resins. Attempts to relate the extents of saturation (with adsorbate) of the exchange sites with the optical densities of the infrared bands were unsuccessful because of deviations from Beer's Law. Ultraviolet spectroscopy failed to provide evidence for charge transfer mechanisms in paraquat-humic acid complexes in aqueous systems.     

Studies of the adsorption of paraquat on soluble humic fractions by gel filtration and ultrafiltration techniques

The adsorption of paraquat dichloride (1,1′-dimethyl-4,4′-bipyridylium dichloride) on a soluble sodium humate fraction of a Fenland soil was studied by gel filtration (on Sephadex G10 and G100) and by ultrafiltration (through an Amicon Diaflo UM-2 ultrafilter). Both methods depend upon the separation, on a molecular weight basis, of the unadsorbed molecules of herbicide from the adsorption complex (consisting of polymeric organic materials and the adsorbed paraquat). Separations were obtained on columns of Sephadex G10 (Method I) and in the ultrafiltration experiments (Method II), and isotherms were prepared from data for adsorption in water (by Method II) and in sodium chloride (by Methods I and II) solutions. Results from the two methods were comparable over the concentration range examined. The increased adsorption of paraquat by Na⁺-compared with Ca²⁺-humate is explained on the basis of the selectivity sequence of humate for exchangeable cations. Attempts to prepare isotherms from gel filtration data, for the adsorption of paraquat on two soluble model humic polymers (polyacrylic acid and a polymer prepared by the oxidative coupling of benzoquinone and ammonium chloride) were unsuccessful because binding to the gel matrix did not permit quantitative recoveries of the adsorption complexes. Paraquat was adsorbed to the same extent on each of four fractions of Na⁺-humate separated on Sephadex G100.     

几种熏蒸剂对貯粮中卡氏长螨熏蒸毒效的探讨

对貯粮为害最大的卡氏长螨用氯化苦进行熏蒸无杀卵毒效,而活动阶段(包括幼虫期、若虫期及成虫期)颇为敏感,致死中量为每升0.28毫克。仓内各种熏蒸方法试验结果,间歇熏蒸法的防治效果较好,能在一定时期内抑制螨害。在七种药剂或配方中,以二溴乙烷和溴甲烷具有更好的杀卵毒效,其致死中量分别为每升2.5毫克和3.4毫克。根据对螨卵的毒效反应,将熏蒸剂分成三种类型:(1)无反应型,如氯化苦。(2)数量反应型,如二氧乙烷。(3)特效型,如二溴乙烷和溴甲烷。     

Maize resistance to northern corn leaf blight is potentiated by nickel

Northern corn leaf blight (NCLB), caused by Exserohilum turcicum, is one of the most devastating diseases affecting maize yield worldwide. A foliar spray of nickel (Ni) to potentiate maize resistance against NCLB was investigated by examining alterations in the photosynthetic apparatus (leaf gas exchange and chlorophyll [Chl] a fluorescence parameters), production of ethylene and reactive oxygen species as well as activities of defence and antioxidant enzymes. Mycelial growth of E. turcicum was inhibited by Ni in vitro. Inoculated plants sprayed with Ni exhibited higher foliar Ni concentration, reduced NCLB symptoms, and lower concentrations of malondialdehyde and hydrogen peroxide. In inoculated leaves of plants not sprayed with Ni, concentrations of Chl a, Chl b, and carotenoids were lower and the photosynthetic apparatus was impaired at the biochemical level due to high NCLB severity. The activities of antioxidant enzymes were not affected by Ni, except an increase in glutathione reductase activity for noninoculated plants sprayed with Ni. High lipoxygenase and polyphenoloxidase activities, lower ethylene production, as well as elevated production of phenolics and lignin helped decrease NCLB severity in the leaves of Ni-sprayed plants.     

A REVIEW OF EXPERIMENTAL WORK WITH DIQUAT AND RELATED COMPOUNDS

Summary. Published literature on diquat (9,10-dihydro-8a, 10a-diazonia phenanthrene dibromide; 1,1'-ethylene-2,2'-dipyridylium dibromide) and related dipyridyl herbicides is reviewed. Their activity is probably connected with the formation of stable free radicals on reduction and both photosynthetic and respiratory processes may be associated with free radical formation in the plants. These herbicides are rapid-acting translocated desiccants and kill the aerial parts of most plants, but are safe as soon as they touch the ground, having no residual effect through the soil. Possible uses are as desiccants, in place of cultivation to clear fallows and seedbeds before sowing, in pre-emergence weedkilling, for weeding round trees and bushes and, with directed spraying, for inter-row weeding in row crops.
Revue des essais effectués avec le Diquat et des composés apparentés     

Removal of paraquat and atrazine from water by montmorillonite‐(Ce or Zr) phosphate cross‐linked compounds

The adsorption of paraquat (1,1′‐dimethyl‐4,4′‐bipyridilium dichloride) and atrazine (6‐chloro‐N ²‐ethyl‐N ⁴‐isopropyl‐1,3,5‐triazine‐2,4‐diamine) from aqueous solution onto two montmorillonite‐(Ce or Zr) phosphate cross‐linked compounds at different temperatures (288 K and 308 K) has been studied using batch experiments. The adsorption isotherms obtained for paraquat on both adsorbents may be classified as H‐type of the Giles classification, which suggests that paraquat molecules are strongly adsorbed on the samples. For the adsorption of atrazine, L‐type isotherms were obtained for both montmorillonite‐(Ce or Zr) phosphate compounds, which suggests that these compounds have a medium affinity for this herbicide. The increase in temperature from 288 K to 308 K did not have any clear effect on the adsorption process of paraquat on either adsorbent whereas atrazine adsorption decreased slightly as temperature increased, possibly due to a mainly physical process. Fourier transform infrared (FTIR) spectroscopic studies revealed that at the pH generated by the adsorbents, the cationic herbicide interacted to a greater extent with the negatively charged surface of the adsorbents than did atrazine. For both herbicides, the Ce‐montmorillonite adsorbent showed a higher adsorption capacity than the Zr‐montmorillonite adsorbent. © 2000 Society of Chemical Industry     

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.     

Approaches to relieving aeration stress in waterlogged plants

A fertile soil contains sufficient water-filled pores to replenish losses by evapotranspiration and to sustain growth. However, too many such pores can be detrimental because the exchange of gases between the soil, plant roots and the aerial environment is impaired by the water they contain (waterlogging). The consequences include an accumulation of metabolically generated gases (such as ethylene), oxygen deficiency and the production of potentially toxic substances. Knowledge of these effects, and their consequences for growth, hormone production and inorganic nutrient uptake, enhance the prospects for ameliorating flooding injury by prophylactic or restorative means. Theexamples described are (a) the use of more porousmedia for plant containers in the nutrient film technique (NFT) of glasshouse crop production; (b) fungistatic, acid neutralising and oxygen-releasing seed coatings; (c) boron and nitrogen fertilisation; (d)foliar applications of cytokinins and gibberellins; (e) the inhibition of ethylene action or stimulation of ethylene production in aquatic species.     

Induction of glutathione S-transterase by fumigants in larvae of the Khapra beetle,Trogoderma granarium (E.)

The effect of fumigants on glutathione and glutathione S-transferase in the Khapra beetle larvae (Trogoderma granarium) was studied by fumigating for 1, 3, and 5 hr with a dose causing 100% mortality at 24 hr of exposure. Glutathione and glutathione S-transferase were assayed in the cytosol at 1, 3, and 5 hr of exposure. Time-dependent depletion of glutathione was seen for all fumigants except carbon tetrachloride and phosphine. The depletion was maximum (60–70%) in the cases of methyl bromide, methyl iodide, and acrylonitrile, and least (20–30%) in the cases of ethylene dibromide and ethylene oxide. The order of glutathione depletion by various fumigants at 5 hr exposure was methyl iodide > methyl bromide = acrylonitrile > ethylene dichloride > ethylene oxide > ethylene dibromide. Glutathione S-transferase was induced by all fumigants except ethylene dibromide, methyl bromide being more potent than methyl iodide. The enzyme induction ranged from 186% by acrylonitrile to 40% by carbon tetrachloride. Mortality above 10% correlated well with the degree of GSH depletion (r = 0.729) whereas the latter did not correlate with the transferase induction.     

不同种子大小籽瓜品种叶片光合能力对源库调节的响应

为了探讨籽瓜叶片光合能力对源库调节的响应,以种子大小显著不同的3个籽瓜品种为材料,于开花坐果期通过整枝、摘叶、疏果将叶果比分别调整为10、20、30、40、50,并分别于幼果期、果实膨大期、果实成熟期测定叶片叶绿素含量及气体交换速率,收获后测定果实产量。结果表明,籽瓜功能叶叶绿素含量（SPAD值）、净光合速率（P_n）、气孔导度（G_s）和蒸腾速率（T_r）随果实生育期演进逐渐降低,胞间CO₂2浓度（C_i）逐渐增大。3个供试品种间SPAD、P_n、G_s、T_r和C_i差异显著,大种子品种H26的气体交换参数（P_n、G_s、C_i、T_i）显著低于中等种子品种H14,H14显著低于小种子品种H3,但SPAD和C_i变化规律相反。叶片SPAD、P_n、G_s、T_r均值及其果实生育期降幅均随叶果比增大而显著降低（叶果比50除外）,但叶片SPAD值和气体交换参数变化幅度无显著的品种间差异,说明一定范围内降低叶果比能提高叶片光合能力,但摘叶处理或叶果比过高均会加速叶绿素降解,诱发叶片衰老。3个品种单株果实产量随叶果比增大而提高,50（1.18 kg）>40（1.17 kg）和30（1.17 kg）>20（1.16 kg）>10（0.87 kg）,H3单株果实产量（0.88 kg）显著低于H26（1.20 kg）和H14（1.25 kg）。以上结果表明,适宜范围的源库比能够提高籽瓜叶片光合能力,延缓叶片衰老,有利于籽瓜果实高产。     

Phototransformation of Dichlorophen in Aqueous Phase

The photolysis of dichlorophen (DCP) in acidic medium yields 4-chloro-4′-hydroxy-2,2′-methylenediphenol ( I ) in the absence of oxygen and a benzoquinone-like derivative ( II ) in oxygenated solution. At pH=9, DCP is in monoanionic form, and three products, I, II and 4-chloro-2,2′-methylenediphenol ( III ) are detected after irradiation of deoxygenated solutions of DCP. Formation of III is also observed in acidic or neutral solutions containing a low percentage of isopropanol. These results can be explained by the formation of a carbene after HCl elimination and reaction of this intermediate with water, oxygen, alcohol, anionic form of I or DCP.     

铵态氮和硝态氮对香蕉枯萎病发生的比较研究

 为寻找降低香蕉枯萎病发生的防治措施,通过室内盆栽接种试验,研究了铵态氮(NH₄⁺-N)和硝态氮(NO₃^--N)对香蕉枯萎病发生及其植株叶绿素含量、气体交换参数、病原菌在植物体内的数量分布和植物钙(Ca)、镁(Mg)、铁(Fe)、钼(Mo)、可溶性糖和木质素含量的效应。结果表明:不接种病原菌的条件下,不同氮素处理对香蕉幼苗生长影响无差异;接菌情况下,与NH₄⁺-N处理相比,NO₃^--N处理显著降低植株各器官的病原菌数量、发病率和发病严重程度。病原菌侵染后,不同氮素处理下植株光合作用均显著下降:NO₃^--N处理香蕉苗保持比NH₄⁺-N处理更高的光合速率;病原菌侵染后NH₄⁺-N处理的植株Ca、Mg、Fe和Mo含量相对于侵染前没有显著差异,但NO₃^--N处理下此4种元素含量均显著升高。病原菌侵染后的植株叶片可溶性糖含量在不同氮素处理中都没有显著变化,但在根系中,NO₃^--N处理的侵染植株可溶性糖含量显著降低。与此同时,病原菌侵染后,木质素含量在NH₄⁺-N处理植株中变化不显著,但其含量在NO₃^--N处理侵染后显著上升。综上所述,NO₃^--N处理可增加植株抗病相关矿质元素的吸收,诱导香蕉苗木质素形成,使其木质化程度增加,从而维持较高的光合作用,保持较高的抗病水平。     

Diphenylether-like physiological and biochemical actions of S-23142, a novel N-phenyl imide herbicide

Several physiological and biochemical actions of a new experimental herbicide, S-23142 [N-(4-chloro-2-fluoro-5-propargyloxyphenyl)-3,4,5,6-tetrahydrophthalimide], have been investigated. S-23142 was active under the presence of light and oxygen. Photosynthetic CO₂ fixation in soybean began to decrease 4–5 hr after the foliar treatment of S-23142, being accompanied by the appearance of visible bleaching and wilting of the plants. A large amount of ethane, the products of peroxidation of unsaturated fatty acids, was produced from the cotyledon discs of cucumber (Cucumis sativus L.) treated with S-23142. Leakage of ATP was also observed. S-23142 did not inhibit photosynthetic oxygen evolution of the discs just after the application; however, the oxygen evolution rate decreased as the treated discs produced ethane. The results suggest that cell membrane and chloroplast membrane were deteriorated by the membrane lipid peroxidation. S-23142 also induced ethylene production and a high level of phenylalanine-ammonia lyase activity in cucumber cotyledon, which was regarded as the phenomena of stress response. Only the ethylene production was inhibited by aminoethoxyvinylglycine and cycloheximide, while the ethane production was not affected. All of these actions of S-23142 were essentially the same as those of acifluorfen ethyl except that the activity of S-23142 was more than 10 times higher than that of acifluorfen ethyl. These data strongly suggest that S-23142 belongs to the same group as diphenylethers in its mechanisms of action despite the difference in chemical structure.     

Collaborative study of the determination of paraquat and diquat in formulated products

Results of a collaborative study undertaken by a Sub-Committee of the Pesticides Analysis Advisory Committee (P.A.C.) of Great Britain to examine analytical methods for paraquat and diquat formulations are quoted. The methods recommended for adoption by the Collaborative International Pesticides Analytical Committee (C.I.P.A.C.), together with procedures for preparation of pure analytical standards of paraquat dichloride and diquat dibromide monohydrate, are given in Appendices I and II respectively.     

Cytochrome P-450 Inducers and Inhibitors Interfering with Ecdysone 20-Monooxygenases and Their Activities during Postembryonic Development of Neobellieria bullata Parker

The cytochrome P-450-dependent microsomal and mitochondrial ecdysone 20-monooxygenase systems convert ecdysone into 20-hydroxyecdysone. The microsomal fraction of fat bodies of zero h wandering stage fleshfly larvae (Neobellieria bullata; Diptera: Sarcophagidae) has a high ecdysone 20- monooxygenase activity. The effects of cytochrome P-450 inhibitors were investigated in vitro on microsomal ecdysone 20-monooxygenase. Metyrapone, fenarimol and certain imidazole derivatives (KK-42, KK-110, KK-135 and PIM) are strong inhibitors. The IC₅₀ value of KK-110, which is the strongest inhibitor, is 2 × 10^?7 M. A triazolyl and two cyclopropylamine derivatives have low activity. The activities of different NADPH-cytochrome c (P-450) reductase inhibitors were also assessed; diquat dibromide is a moderate inhibitor of microsomal ecdysone 20-monooxygenase, while paraquat dichloride has no activity. In-vivo experiments with cytochrome P-450 inducers and inhibitors gave the following results: (a) fenarimol, FI-121, precocene-2 caused “permanent” first-instar larvae; (b) barbital, phenobarbital and their sodium salts caused significant delay in larval development; (c) PIM, PTM, metyrapone, KK-42, KK-135, J-2710, RH 5849 and colchicine caused moulting disturbances; (d) J-2710, PIM, PTM, KK-42, KK-135, RH 5849 and colchicine caused lethal spiracle and mandible malformation; (e) KK-110, fenarimol, barbital and phenobarbital caused precocious pupariation.     

Effects of EPTC, fluorodifen and monuron on transpiration and photosynthetic oxygen output in Eupatorium odoratum plants

The influence of foliar sprays of EPTC, fluorodifen and monuron on transpiration and photosynthetic oxygen output of Eupatorium odoratum plants is demonstrated. Foliar sprays with 100 ppm EPTC or monuron led to a significant decrease in transpiration for a continuous period of 14 days. Treatment with 100 ppm fluorodifen led to a noticeable increase in transpiration during the first eight days. All three herbicides significantly reduced photosynthetic oxygen output from the Eupaiorium plants. EPTC and monuron however, gave greatest effect. Reduction in transpiration from the plants was due to stomatal closure while reduction in photosynthetic oxygen output was due to both stomatal closure and probably also inhibition of the Hill reaction.     

干旱胁迫对两种辣椒叶片气体交换和叶绿素荧光特性的影响

试验研究了干旱条件下鸡爪×吉林和正椒13号两种辣撤叶片气体交换和叶绿素荧光参数的变化.结果表明,干旱处理5 d导致叶片相对含水量(RWC)、相对电导率(REC)、净光合作用(Pn)和暗适应下PSII最大光化学效率(Fv/Fm)下降,其中对鸡爪×吉林影响大于正椒13号.干旱处理下两辣椒品种的气孔导度(Gs)下降,而水分利用效率(WUE)、非光化学猝灭系数(NPQ)和光呼吸速率/净光合速率(Pr/Pn)均明显增加,其中正椒13号上升幅度高于鸡爪×吉林,这可能是正椒13号比鸡爪×吉林更耐旱的原因.     

蔓枯病菌侵染影响抗感甜瓜品种及杂种的光合特性分析

 以抗病的甜瓜“PI157082”、“PI482398”和杂种1代“PI157082×PI482398”以及感病品种“白皮脆”为材料,研究了蔓枯病菌接种对甜瓜幼苗叶片叶绿素含量、气体交换参数和叶绿素荧光参数的影响。结果表明:蔓枯病菌接种后,不同抗性甜瓜的叶绿素含量、净光合速率、气孔导度、Fv/Fm、Fv′/Fm′和ΦPSII均有不同程度的降低,CO₂浓度均有不同程度的上升。感病品种“白皮脆”的净光合速率、Fv′/Fm′、ΦPSII早于抗病材料达到显著水平;叶绿素含量、Fv/Fm显著低于接种前的时间跨度比抗病材料长;CO₂浓度变化幅度比抗病材料大。在抗病材料中,杂种1代PI157082×PI482398的净光合速率、Fv′/Fm′显著降低的时间晚于亲本PI157082和PI482398;叶绿素含量、气孔导度、Fv/Fm一直与接种前差异不显著;CO₂浓度变化幅度比亲本PI157082和PI482398小,说明杂种1代PI157082×PI482398可能比双亲有更严密的防御机制,使幼苗叶片保持较高的光合速率,体现出一定的杂种优势。     

蔓枯病菌侵染影响抗感甜瓜品种及杂种的光合特性分析

 以抗病的甜瓜“PI157082”、“PI482398”和杂种1代“PI157082×PI482398”以及感病品种“白皮脆”为材料,研究了蔓枯病菌接种对甜瓜幼苗叶片叶绿素含量、气体交换参数和叶绿素荧光参数的影响。结果表明:蔓枯病菌接种后,不同抗性甜瓜的叶绿素含量、净光合速率、气孔导度、Fv/Fm、Fv′/Fm′和ΦPSII均有不同程度的降低,CO₂浓度均有不同程度的上升。感病品种“白皮脆”的净光合速率、Fv′/Fm′、ΦPSII早于抗病材料达到显著水平;叶绿素含量、Fv/Fm显著低于接种前的时间跨度比抗病材料长;CO₂浓度变化幅度比抗病材料大。在抗病材料中,杂种1代PI157082×PI482398的净光合速率、Fv′/Fm′显著降低的时间晚于亲本PI157082和PI482398;叶绿素含量、气孔导度、Fv/Fm一直与接种前差异不显著;CO₂浓度变化幅度比亲本PI157082和PI482398小,说明杂种1代PI157082×PI482398可能比双亲有更严密的防御机制,使幼苗叶片保持较高的光合速率,体现出一定的杂种优势。