Germination of Chromolaena odorata (L.) K. & R. achenes: effect of storage, harvest locality and the pericarp     

D. J. ERASMUS  J. VAN  STADEN 《Weed Research》1987,27(2):113-118

The percentage germination of achenes of Chromolaena odorata (L.) K. & R. stored dry in the dark at 25°C for 7 months was markedly higher than that of freshly harvested achenes. This is indicative of an after-ripening requirement that may be of benefit to the species by ensuring temporal distribution of germination. Germination of freshly harvested achenes from various sites differed. However, after 7 months of dry, dark storage at 25°C no differences were present, thus, confirming the after-ripening requirement. Although the total number of achenes per capitulum did not vary from site to site, there were distinctive differences in the number of filled (presumably viable) achenes. It is suggested that this is a reflection of the environmental conditions prevailing at the sites. Puncturing of the achene pericarp did not influence dark germination but its removal increased percentage germination significantly. Natural degradation of the pericarp in the field may, therefore, permit germination of buried achenes in the absence of a suitable light stimulus.  相似文献   

Effects of crop species, crop cultivars and isolates of Verticillium dahliae on the population of microsclerotia in the soil, and consequences for crop yield     

L. MOL  J. M. VAN HALTEREN  K. SCHOLTE  & P. C. STRUIK 《Plant pathology》1996,45(2):205-214

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Effect of crop age on primary gradients of late leaf spot (Cercosporidium personatum) on groundnut     

S. SAVARY  G. VAN  SANTEN 《Plant pathology》1992,41(3):265-273

Artificial sources of late leaf spot were established by inoculation of one plant at the centre of several groundnut plots differing in age. First-generation dispersal and resulting primary gradients of disease were then compared. The gradients were corrected for source strength, spontaneous infection (primary gradient), and interplot interference (first-generation dispersal). The shapes of the gradients for spore dispersal and of the gradients of disease corresponded for each age of groundnut plot, but differed between the ages. The slopes of gradients were steeper in the older plots. Spore dispersal and the resulting disease gradients were not isodiametric, gradients being most protracted in a north-to-north westerly direction. The results suggest that the strength of the sources was reduced by abscission of infected leaves in the sources of the younger plots, whereas accessibility of the canopy to the transported spores was reduced by increasing canopy density in the older ones.  相似文献   

A dynamic model simulating infection of apple leaves by Venturia inaequalis   总被引：2，自引：0，他引：2  

X.-M. XU  D. J. BUTT  G. VAN  SANTEN 《Plant pathology》1995,44(5):865-876

A new dynamic model of the infection of apple leaves by Venturia inaequalis is described. The model begins with the release of spores by rain and incorporates the effect of light on the discharge of ascospores from pseudothecia. The model then simulates infection through the sub-processes of germination, appressorium formation and penetration, separately for ascospores and conidia landed concurrently on wet leaves. The rate of the infection process is determined using different equations for ascospores and conidia. Spore mortality when leaves dry is determined by the stage of infection and RH in the dry period. The infection process is driven by surface wetness, temperature and RH. The progress of each infection period is measured as infection efficiency (IE), namely the percentage of landed spores which have penetrated and thereby infected leaves. The final IE quantifies the favourability of weather in each infection period. In orchard tests in each of three years, the new model detected crucial infection periods in spring and early summer which accounted for outbreaks of leaf scab. These periods were not detected by a static model based on Mills'criteria. The models performed similarly in detecting infection periods later in summer.  相似文献   

Has bovine somatotropin (BST) an effect upon drug disposition? Comparative studies in goats and cattle with sulphadimidine and antipyrine after parenteral administration of BST,zeranol and proligestone     

R. F. WITKAMP  S. M. NIJMEIJER  C. T. M. VAN DUIN  M. M. BEVERS  TH. WENSING†  H. VAN GOGH  A.S.J.P.A.M. VAN MIERT 《Journal of veterinary pharmacology and therapeutics》1989,12(2):163-178

Daily subcutaneous BST injection in lactating cows, bulls and castrated male dwarf goats did not induce significant changes in the pharmacokinetic parameters of antipyrine (AP) and sulphadimidine (SDD). Similarly, no changes were obtained after injection of slow-release BST formulations in lactating cows and non-lactating female goats. In contrast to androgenic hormones, both zeranol and proligestone had no effect upon the disposition of AP and SDD, although both synthetic hormones did induce enhanced plasma somatotropin concentrations. In goats, metabolic effects induced by zeranol and BST included significant reductions in plasma urea values, whereas plasma creatinine levels were somewhat lower after daily BST administration.  相似文献   

Components of partial resistance to potato blackleg caused by pectolytic Erwinia carotovora subsp. atroseptica and E. chrysanthemi     

J. J. H. M. ALLEFS  W. VAN DOOIJEWEERT  W. PRUMMEL  L.C.P. KEIZER  & J. HOOGENDOORN 《Plant pathology》1995,45(3):486-496

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Responsibility of state and federal agencies in control of animal diseases transmissible to man     

VAN HOUWELING CD 《Journal of the American Veterinary Medical Association》1957,130(1):1-3

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Testing of Imported Potato Genotypes for Potato Spindle Tuber Viroid with a Tomato-intermediate /Electrophoresis Combined Method     

W.M.J. VAN Gelder  A. Treur 《EPPO Bulletin》1982,12(4):297-305

The polyacrylamide gel electrophoresis (PAGE) test of Morris & Smith (1977) was evaluated for detection of potato spindle tuber viroid (PSTV) in breeding material. Number, density and mobility of nucleic acid bands in the electropherograms were influenced by genotype and growing temperature. So direct testing of genotypes was not reliable. After an intermediate viroid multiplication in tomato host plants at about 30oC and high irradiance, PSTV was reliably detectable with PAGE in inocula of potato samples of diverse origin. A 4-week incubation period proved to be suitable for inocula with low and high concentrations of a mild strain of PSTV (m-PSTV) as well as a severe strain of PSTV (s-PSTV). If incidence of PSTV is expected to be low, testing can be speeded up by bulking samples. With the combined tomato-intermediate/ PAGE assay, one m-PSTV or one s-PSTV infected leaf disk in 200 healthy ones was consistently detectable. Occasionally gels with a nucleic acid band of about the same relative mobility as the viroid band were found. Evidence that these bands were not caused by viroid is presented. A procedure to resolve such questionable test results is described. Infectivity of s-PSTV was higher than that of m-PSTV. Concentration of viroids in the inoculum influenced appearance of mild or severe symptoms and the rate of symptom production.  相似文献   

The pharmacokinetics and tissue levels of polymyxin B, colistin and gentamicin in calves   总被引：1，自引：0，他引：1  

G. ZIV  J. F. M. NOUWS  C. A. M. VAN  GINNEKEN† 《Journal of veterinary pharmacology and therapeutics》1982,5(1):45-58

Following a single intravenous injection of polymyxin B, colistin (5 mg/kg, each) and gentamicin (3 mg/kg) to calves, the decline in serum antibiotic concentration generally suggested a three-compartment (open system) pharmacokinetic model. Tissue binding is a dominant factor in the distribution and elimination kinetics of the drugs. Less than 65% of the dose of polymyxin B and colistin was recovered in the urine during 48 h after treatment. Concentrations of nonbound polymyxin B and colistin in the kidney, liver, lung, heart, and skeletal muscles were similar to total (free and bound) serum drug levels, but considerably higher concentrations were found, in bound form, in chloroform-ethanol extracts of these organs.
At 24 h after treatment, more than 50% of the doses of polymyxin B and colistin were present bound to the tissues; the largest amount was in the skeletal muscles. Gentamicin was concentrated in the kidney, predominantly in the free form. At 48 h after treatment the amount of gentamicin in the kidney was 6.3% of the administered dose, being more than five times greater than the corresponding amounts of polymyxin B and colistin.
The extent of tissue uptake of polymyxin B and colistin limits the usefulness of kinetic values, which are derived from the analysis of serum drug levels, for the purpose of designing dosage schedules. The strong affinity of the polymyxins to the muscle tissue, and gentamicin to the kidney, can result in drug residues persisting in the body for several weeks.  相似文献   

Determination of red blood cell potassium content in horses with diarrhoea: A practical approach for therapy     

E. MUYLLE  J. NUYTTEN  C. VAN DEN HENDE  P. DEPREZ  K. VLAMINCK  W. OYAERT 《Equine veterinary journal》1984,16(5):450-452

The concentration of potassium in the red blood cells in 15 horses with severe diarrhoea was determined. The red blood cell potassium content (RBCK⁺) was low compared with levels obtained in normal horses. The decrease in the RBCK⁺ was used to evaluate the total body potassium deficit. This calculated amount was administered orally, following each RBCK⁺ determination. In those horses which recovered, RBCK⁺ content returned to normal levels. During treatment, refilling of the red blood cells with potassium occurred only gradually as long as the diarrhoea persisted. In each case, oral loading with the calculated dose resulted in an improvement of the general condition and no side effects were observed. The importance of using RBCK⁺ levels as a diagnostic and therapeutic parameter is discussed.  相似文献