摘要:

AbstractRemote and relatively inaccessible parts of plants such as roots and meristematic tissue can readily be reached by foliar‐applied xenobiotics if the latter are capable of entering into and moving in the phloem Development of a passivetransport model provides a description of the time course of this movement and its dependence upon the physical properties of the chemical and the condition of the plant vascular system. The model so developed is used to formulate principles for rendering otherwise non‐systemic xenobiotics phloem‐mobile. These principles can be categorized according to the nature of the chemical modifications that facilitate phloem translocation. These modifications include (a) sugar conjugation, (b) acid functionalization, and (c) formation of quaternary salts from basic parents. The potential of these modifications to facilitate the phloem translocation of wide range of pesticides is disc

ISSN:0031-613X    

DOI:10.1002/ps.2780420102

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractA linear relationship (r2= 0.99) was found between the concentration of acephate in the nutrient solution applied to gerberas (Gerbera jamesoniiH. Bollus ex Hook. f) grown in perlite and the mortality of nymphs of greenhouse whitefly,Trialeurodes vaporariorumWestwood. The LD50for this method of application was 84 mg litre−1. A single irrigation with 180 mg litre−1acephate killed all nymphs in 10 days without apparent damage to plants. At 120 mg litre−1, acephate accumulated readily in leaves, reaching a maximum concentration of 11 mg kg−1dry matter on the third day of treatment. Concentrations in leaves then fell gradually, reaching 50% of the maximum concentration seven days later. Methamidophos was first detected in leaves approximately a day later than acephate. A maximum concentration of 9 mg kg−1dry matter was recorded on day 5 after which the concentration slowly fell. The half‐life of methamidophos was estimated to be 11 days. The systemic use of acephate for the control of greenhouse whitefly and its relevance to Integrated Pest Management (IPM) programmes for pests of ornamental plants ar

ISSN:0031-613X    

DOI:10.1002/ps.2780420103

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractThe uptake of five xenobiotic chemicals (cinmethylin, cyanazine, hyformal, oxamyl and phenylurea) by isolated phloem strands and storage‐parenchyma tissues of celery (Apium graveolensL var.dulce) has been assessed with respect to time, substrate concentration, pH and efflux characteristics. Absorption by phloem tissue was by a diffusion‐like process which did not become saturated within the time investigated. In contrast, uptake by parenchyma tissue approached saturation within 6 h. Uptake of the various chemicals demonstrates different responses to the pH of the incubation solutions and the chemicals showed different retention characteristics within the phloem and parenchyma tissues. The use of physico‐chemical properties (logKowand pKa) to predict the behaviour of these xenobiotic chemicals within celery tissue is disc

ISSN:0031-613X    

DOI:10.1002/ps.2780420104

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractA series of novel 2,3‐dibromo‐5‐trifluoromethyl‐4‐pyrrolecarboxylates were prepared and their herbicidal properties evaluated. Several compounds showed strong herbicidal efficacy after post‐emergence application onto the green parts of the test plants. Speed of action as well as the activity symptoms suggest that these novel pyrrole herbicides may act like halogenated 4‐hydroxybenzonitrile derivatives or d

ISSN:0031-613X    

DOI:10.1002/ps.2780420105

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractA factorially designed set of 3‐substituted 2‐aryl‐4,5,6,7‐tetrahydroindazoles was synthesized and their herbicidal properties were evaluated using regression analysis. For optimal activity, the substituent at position 3 should be neither strongly hydrophobic nor hydrophilic and should have a small minimum radius. A study of the mechanism of action indicated that the tetrahydroindazoles are inhibitors of the enzyme protoporphyrinogen

ISSN:0031-613X    

DOI:10.1002/ps.2780420106

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractThe rate of loss of [14C]carbofuran, and the rate of formation of metabolites from it, were studied in a ‘treated’ soil, in which the insecticide was rapidly degraded. Metabolic inhibitors were added to the soil to study their effects upon these processes. The organophosphorus compounds paraoxon, chlorfenvinphos, and disulfoton, which, in their active forms, are inhibitors of ‘B’ esterases, all caused a temporary reduction of the rate of loss of carbofuran from the soil. However, within a period of 3–21 days, depending on the compound, the soil recovered its ability to break down carbofuran rapidly. The incorporation of both piperonyl butoxide (an inhibitor of oxidations catalysed by monooxygenases which contain cytochrome P450) and paraoxon into soil reduced the rate of loss to a greater extent and over a longer period than was found with paraoxon alone. Where soils were treated with paraoxon alone, or with paraoxon plus piperonyl butoxide, larger quantities of the primary oxidative metabolites 3‐keto‐carbofuran (<4.1% of applied carbofuran) and 3‐hydroxy‐carbofuran (<1.2% of applied carbofuran) were found than in control soils in which the corresponding values were<0.54% and<0.43% respectively.The results were consistent with the hypothesis that inhibition of microbial enzymes was the main reason for the stabilization of carbofuran in this soil following treatment with these compounds. The evidence suggested that esterase hydrolysis provided a major rate of breakdown, whilst oxidative metabolism provided a minor one. The higher levels of oxidative metabolites in soils treated with paraoxon and paraoxon plus piperonyl butoxide were thought to be due to the inhibition of their further metabolism. The possible use of certain of these compounds as ‘extenders’ for carbofuran in probl

ISSN:0031-613X    

DOI:10.1002/ps.2780420107

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractChlorpyrifos [O,O‐diethylO‐(3,5,6‐trichloro‐2‐pyridyl) phosphorothioate] is an organophosphorus insecticide applied to soil to control pests both in agricultural and in urban developments. Typical agricultural soil applications (0.56 to 5.6 kg ha−1) result in initial soil surface residues of 0.3 to 32 μg g−1. In contrast, termiticidal soil barrier treatments, a common urban use pattern, often result in initial soil residues of 1000 μg g−1or greater. The purpose of the present investigation was to understand better the degradation of chlorpyrifos in soil at termiticidal application rates and factors affecting its behaviour. Therefore, studies with [14C]chlorpyrifos were conducted under a variety of conditions in the laboratory. Initially, the degradation of chlorpyrifos at 1000 μg g−1initial concentration was examined in five different soils from termite‐infested regions (Arizona, Florida, Hawaii, Texas) under standard conditions (25°C, field moisture capacity, darkness). Degradation half‐lives in these soils ranged from 175 to 1576 days. The major metabolite formed in chlorpyrifos‐treated soils was 3,5,6‐trichloro‐2‐pyrid‐inol, which represented up to 61% of applied radiocarbon after 13 months of incubation. Minor quantities of [14C]carbon dioxide (<5%) and soil‐bound residues (⩽ 12%) were also present at that time. Subsequently, a factorial experiment examining chlorpyrifos degradation as affected by initial concentration (10, 100, 1000 μg g−1), soil moisture (field moisture capacity, 1.5 MPa, air dry), and temperature 15, 25, 35°C) was conducted in the two soils which had displayed the most (Texas) and least (Florida) rapid rates of degradation. Chlorpyrifos degradation was significantly retarded at the 1000 μg g−1rate as compared to the 10 μg g−1rate. Temperature also had a dramatic effect on degradation rate, which approximately doubled with each 10°C increase in temperature. Results suggest that the extended (3–24 + years) termiticidal efficacy of chlorpyrifos observed in the field may be due both to the high initial concentrations employed (termite LC50= 0.2– 2 μg g−1) and the extended persistence which results from employment of these rates. The study also highlights the importance of investigating the behaviour of a pesticide under the diversity of agr

ISSN:0031-613X    

DOI:10.1002/ps.2780420108

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractNaproanilide [2‐(2‐naphthyloxy)propionanilide] has a high activity against dicotyledonous weeds in rice fields, but is very safe to rice. This study was designed to clarify the absorption and translocation of radiolabelled naproanilide in tobacco plants and the metabolism in tobacco callus. The results indicated that naproanilide is translocated easily to the upper part of tobacco plants. Distribution of radioactivity in tobacco plants at the 7th day was shown to be 0.88, 0.24 and 0.03%, and at the 14th day 1.71, 1.86 and 2.32% of the total activities of [14C]naproanilide in root, stem and leaf, respectively. When compared to earlier results obtained with rice, the translocation rate in tobacco is much higher and might therefore contribute a possible mechanism of herbicidal selectivity. Metabolites including NOP [2‐(2‐naphthyloxy)propionic acid], NOPM [methyl 2‐(2‐naphthyloxy)propionate], 2‐naphthol, 2,3‐naphthalenediol, 2,6‐naphthalenediol, 2,7‐naphthalenediol and 2‐hydroxy‐1,4‐naphthoquinone were identified in tobacco ca

ISSN:0031-613X    

DOI:10.1002/ps.2780420109

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractThis study attempts to use [3H] α‐endosulfan to examine directly the binding site(s) for cyclodienes, lindane and toxaphene (collectively referred to as the polychlorocycloalkane or PCCA insecticides) in the 4‐aminobutyric acid (GABA)‐gated chloride channel. [3H] α‐Endosulfan was prepared by reduction of hexachloronorbornenedicarboxylic anhydride with sodium borotritide, then coupling the labelled alcohol with thionyl chloride followed by HPLC purification (35 Ci mmol−1,>99% radiochemical purity). This new candidate radioligand readily partitions into lipid membranes and undergoes indiscriminate adsorption to surfaces resulting in high levels of non‐specific binding. This makes it very difficult to differentiate the small portion of specific binding at the site relevant to toxic action. This problem was partially circumvented by incubating [3H] α‐endosulfan (0.1 nM) with house‐fly head membranes (0.2 mg protein) for 70 min at 22°C giving 23 (±4)% specific binding (40 fmol mg−1protein) determined as the difference between the radioligand alone and on preincubation for 15 min with unlabelled α‐endosulfan (final concentration 100 nM). This procedure is not appropriate for determination of saturation isotherms and standard binding kinetics. However, the effectiveness of 16 PCCAs (also at 100 nM final concentration) in blocking the specific binding of [3H] α‐endosulfan is generally consistent with their relative potencies as inhibitors of 4‐[3H] propyl‐1‐(4‐ethynylphenyl)‐2,6,7‐trioxabicyclo[2.2.2]octane ([3H]EBOB) binding suggesting that the binding site for both [3H]α‐endosulfan and the PCCAs is part of the GABA‐gated chloride channel. Insecticidal channel blockers of other types (e.g. picrotoxinin, trioxabicyclooctanes, a dithiane, and phenylpyrazoles) and GABA are poor inhibitors of [3H] α‐endosulfan binding relative to their potencies as inhibitors of [3H] EBOB binding. It therefore appears that the PCCAs compete directly for the [3H] α‐endosulfan site, whereas the other channel blockers bind with different inhibition kinetics or at a site more closely coupl

ISSN:0031-613X    

DOI:10.1002/ps.2780420110

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractIntercropping field vegetables with other species such as clovers shows insect pest suppression which may make chemical control unnecessary. Examples are given to illustrate these effects and the underlying mechanisms are discussed. Intercropping fits into environmentally acceptable and sustainable vegetable‐producing practices. Both economic and ecological conditions must be fulfilled before intercropping‐based commercial production methods can be develo

ISSN:0031-613X    

DOI:10.1002/ps.2780420111

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY