摘要:

AbstractMechanisms of surfactant/wax interactions which contribute significantly to the acceleration of rates of cuticular uptake of agrochemicals have been investigated. Experiments were carried out using isolated and subsequently reconstituted barley wax. As14C‐labelled model compounds, the monodisperse alcohol ethoxylate octaethyleneglycolmonododecylether (C12E8), the aromatic compound, pentachlorophenol (PCP), and the aliphatic tetracosanoic acid (C24AC; representing a typical wax constituent) were used. Each of the three compounds represented one part of the complete interacting system: surfactant, pesticide and wax. Partitioning of PCP was independent of simultaneously present C12E8below its critical micelle concentration (CMC), but decreased linearly above the CMC. The maximum increase in the mobility of PCP was by a factor of about four by C12E8, whereas the maximum increase of the mobility of C24AC was about forty‐fold. Effects on the mobility of PCP andC24AC were independent of C12E8concentrations above the CMC, but they decreased significantly with decreasing C12E8concentrations below the CMC. A common model usually applied in life sciences for the analysis for dose‐response curves, relating the observed effects to the logarithms of the applied concentrations, was successfully fitted to the results obtained here. This indicated that the observed effects were a function of the relative, rather than absolute, concentrations of the surfactant within the wax. Furthermore, it was discovered that surfactant‐induced acceleration of the diffusion of PCP and C24AC was completely reversible if C12E8was removed from the system. Thus, accelerating effects on diffusion only occurred if distinct amounts of surfactant were present within the wax. This, finally, led to a tentative model, explaining the effect of C12E8on wax structure as an unspecific plasticising interaction between surfactant and wax. Rapid induction and complete reversibility of the effects indicated that the assumption of irreversible alterations of the wax structure (e.g. solubilisation of wax or destruction of crystalline wax domains) was not necessary in order to explain the surfactant‐induced acceleration of rates of cuticular permeation of pesticides, when studying absorption/desorption from non‐evaporating aqueous solutions. However, such changes may still occur when evaporation of the water in spray deposits concentrates surfactants sufficiently for them to become w

ISSN:0031-613X    

DOI:10.1002/ps.2780450102

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe organophosphate veterinary insecticide coumaphos [O‐3‐chloro‐4‐methyl‐2‐oxo‐2H‐chromen‐7‐ylO, O‐diethyl phosphorothioate] is used by the Animal and Plant Health Inspection Service of the United States Department of Agriculture in its program designed to prevent re‐entry of the southern cattle tick (Boophilus microplusCan.) and the cattle tick (B. annulatusSay) into the United States from Mexico. Large amounts of waste acaricide are generated annually in this program. One event that triggers disposal of coumaphos dips is the accumulation of potasan [O, O‐diethylO‐4‐methyl‐2‐oxo‐2H‐chromen‐7‐yl phosphorothioate]. This process was shown to occur under anaerobic conditions and to be inhibited by mercury ions, indicating that anaerobic micro‐organisms were responsible for a reductive dechlorination. Maintaining coumaphos suspensions at pH<7 prevented the reductive dechlorination of coumaphos and left a suspension that was amenable to disposal by biodegradation. A field trial on an 11000‐litre capacity coumaphos dipping vat demonstrated the applicability of using acid to extend the life of coumaphos solutions and of biod

ISSN:0031-613X    

DOI:10.1002/ps.2780450103

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractA method for the analysis of imazapyr [2‐(4‐isopropyl‐4‐methyl‐5‐oxo‐2‐imidazolin‐2‐yl)nicotinic acid] residues in tropical and temperate soils was developed. Imazapyr residues, extracted from soil with ammonium hydrogen carbonate and cleaned‐up by centrifuging, anion‐exchange solid‐phase extraction (SPE), pH adjustment, and C18SPE, were determined by HPLC. Recoveries from soils from Hawaii (Halii sandy clay loam), Texas (Houston Black clay), and Maryland (Codorus loam), USA, fortified with imazapyr (0‐5 μg g−1soil) and equilibrated for 12‐18 h, were 99(±3)%, 104(±4)% and 89(±2)%, respectively. Recoveries were independent of fortification level, but dependent upon soil type. Methods previously described in the literature produced imazapyr recoveries of less than 60% with Halii soil. This improved method has a limit of detection of 5 ng g−1(equivalent to or better than other methods) and affords higher recovery of

ISSN:0031-613X    

DOI:10.1002/ps.2780450104

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe vapour pressure of thermally stable substances can be determined easily at ambient pressure using the evaporation rate method. It is possible to measure the evaporation by thermogravimetry in the temperature range from 30°C to 800°C. Vapour pressures as low as 10−10Pa (10−12mbar) can be determined with excellent reproducib

ISSN:0031-613X    

DOI:10.1002/ps.2780450105

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe effect of timed protectant applications of pyrimethanil on the natural infection process of isolates ofBotrytis fabaeSardina on broad bean leaves was investigated using a range of light and electron microscopic techniques. At 400 mg litre−1, there was some inhibition of spore germination, and a significant reduction in germ tube extension. These responses were variable between isolates, treatment times and dose rates. Appressorium formation and function (i.e. penetration of the host epidermis) were not affected. However, there was a significant reduction in the numbers of host cells killed at each penetration site, resulting in retarded, or, with some isolates, arrested lesion development. This response was similar for all isolates tested. The likely mode of action of pyrimethanil as a pathogenesis inhibitor is discusse

ISSN:0031-613X    

DOI:10.1002/ps.2780450106

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe effect of pyrimethanil on the levels of cell wall degrading enzymes secreted byBotrytis cinereaPers. was investigated in diseased plant tissues and in liquidB. cinereacultures. Total proteinase activity isolated from infected carrot slices which were treated with 5.0 μM pyrimethanil was decreased by 76%, 3 d after inoculation. Polygalacturonase, cellulase, proteinase and laccase activities were all decreased in the medium of three day‐old cultures grown in the presence of pyrimethanil. The pyrimethanil concentrations resulting in 50% reduction in total enzyme activities (IC50) were approximately 0.25 μM for polygalacturonase, cellulase and proteinase, and approximately 1.0 μM for laccase. No significant growth inhibition was observed at these pyrimethanil concentrations. Pyrimethanil did not inhibit the enzymes directly, nor did it inhibit the synthesis of cytosolic proteins. Therefore, it was proposed that the fungicide inhibits protein secretion at a post‐translational stage in the secretory pathway.Large differences were found in the effects of pyrimethanil on the growth ofB. cinereain liquid cultures and on agar plates, depending on the composition of the medium. In liquid media containing cellulose and protein as carbon and nitrogen sources, growth inhibition occurred at 5.0 μM pyrimethanil, whilst no growth inhibition was observed with 50 μM pyrimethanil in malt extract. Similarly, growth occurred on potato/dextrose agar (PDA) at 0.5 μM pyrimethanil, but no growth was seen at this concentration on agars containing cellulose and protein. Thus it appears that pyrimethanil is most active in media where the fungus has to utilise extracellular enzymes to mobilise the nutrients it requires f

ISSN:0031-613X    

DOI:10.1002/ps.2780450107

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractScreening for fungicidal activity carried out on culture broths of soilStreptomycesstrains resulted in the isolation of two new macrolide polyene antibiotics. AB021‐a and AB021‐b, endowed with good protective activity against some plant diseases. These compounds had no effect on seed germination or seedling development, while they strongly inhibited the growth of rice, carrot and periwinkle cells in liquid suspension culture. This inhibition may be ascribed to the lack of the cuticular barrier in these materials. Within a short period of incubation, some parameters connected with membrane permeability of rice, carrot and periwinkle cells were affected. An increase of oxygen consumption also occurred. Incubation of beetroot discs with AB021 led to increased conductivity of the external medium. In addition, a leakage of betacyanin occurred, suggesting a modification of transport processes, also at the tonopl

ISSN:0031-613X    

DOI:10.1002/ps.2780450108

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe effects of the fungicides, flutriafol, triadimenol and an experimental compound (2,2‐dimethyl‐3‐(2‐chlorobenzyl)‐4‐(1,2,4‐triazol‐1‐yl)‐butan‐3‐ol), on conidial viability and lipid composition, have been examined in strains of barley and wheat powdery mildew (Erysiphe graminisDC.) sensitive or resistant to DMI fungicides. In the absence of fungicides, these strains had the same sterol composition, regardless of their sensitivity to DMIs. Following treatment with the compounds, conidia contained eburicol and obtusifoliol, indicating inhibition of the 14α‐demethylase. There was also an accumulation of episterol, suggesting that introduction of the 5,6‐double bond was also inhibited. The changes in sterol composition induced by the fungicides were small. The fatty acid composition of sensitive and resistant strains was also determined. Triadimenol treatment caused an increase in the saturation of C22and C24acids in all strains examined, but changes were not correlated with the biological effects of the fungicide. No single mechanism of resis

ISSN:0031-613X    

DOI:10.1002/ps.2780450109

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe movement of [14C]pyridinecarboxylic acids was investigated in the castor bean plantRicinus communisL. after application by petiole injection. The three isomeric unsubstituted acids appeared in similar concentrations in phloem sap taken from the upper main stem over a period of 6 h after application, but nicotinic acid occurred at higher concentrations than its isomers in phloem sap from the lower stem indicating better retention in the phloem sieve tubes. After 24 h, nicotinic acid had accumulated to a greater extent in the phloem sinks than had picolinic or isonicotinic acids. Phloem transport of substituted analogues, including dihalopyridinecarboxylic acids and imidazolinone herbicides, was measured in short‐term tests, and attempts made to relate such transport to the lipophilicity and pK,aof the compounds. Analogues of the imidazolinone, imazapyr, were less well transported than imazapyr itself, and were also much less well taken up by barley roots from nutrient solution compared to the herbicidal imidazolinone, and this could explain their low herbicidal efficacy despite a high intrinsic activity against the target enzyme acctolactate synthas

ISSN:0031-613X    

DOI:10.1002/ps.2780450110

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractFour examples are given of how discussion between scientist and statistician enhanced both the analysis and interpretation of experimental data. They cover both the design and analysis of field experiments, and some of the problems associated with interpreting data from dose‐response assays. There is little doubt that the statistician, with his array of analytical and diagnostic tools, can often improve a scientist's interpretation of experimental data, although a statistician cannot compensate for a poorly designed or inadequately replicated experimen

ISSN:0031-613X    

DOI:10.1002/ps.2780450111

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY