摘要:

The rate at which the Rothamsted tobacco necrosis virus (RTNV) accumulates in inoculated French bean leaves increases with rising temperature to 22°C. and then decreases. Three days after inoculation, leaves at 22°C. contain 4000 times as much virus as at 10°C. and 1000 times as much as at 30°C. At all temperatures the rate of accumulation may depend on the balance between synthesis and inactivation of RTNV, but inactivation becomes increasingly important with rise of temperature above 22° C. and as the virus content of the leaves increases. Above 22°C. the rate of multiplication may increase but less rapidly than the rate of inactivation, and exposing inoculated leaves to ultra‐violet radiation at various intervals after inoculation suggests that at 30°C. RTNV multiplies in and moves from the initially infected epidermal cells in slightly less than the 6 hr. needed at 22°C. Thirty hr. are needed at 10°C. Newly formed virus is rapidly inactivated at 30°C. Raising the ambient temperature also decreases the numbers of local lesions produced by RTNV, possibly by increasing the chances that the introduced virus particles will become inactivated. Increasing the virus content of the inoculum above the level giving one lesion per sq.cm. does not increase the subsequent virus content of inoculated leaves.At temperatures of 30°C. and below, tomato aucuba mosaic virus produces necrotic lesions in leaves of tobacco andNicotiana glutinosawhereas above 30°C. the lesions are chlorotic. In both hosts this virus multiplies more rapidly when the infected cel

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1956.tb02117.x

出版商:Blackwell Publishing Ltd    

年代:1956

数据来源: WILEY

摘要:

Leaves of tobacco plants inoculated with tobacco mosaic virus were divided into three groups: (a) inoculated leaves; (b) younger non‐inoculated leaves present at the time of inoculation; (c) leaves formed since inoculation. The respiration rate of each group was compared with that of similar leaves from healthy plants. The respiration rate of inoculated leaves was increased by a constant amount for 3 weeks after inoculation, when it decreased. The respiration rate of group (b) leaves was not affected at any time, and that of group (c) leaves was decreased by 10% when they showed symptoms. The increased respiration in the inoculated leaves occurred too soon to reflect virus formation, and it is suggested that it reflects an initial change in infected cells preparatory to virus synthesis. The subsequent decrease in respiration may be due to the accumulation of virus which does not contribute to the total leaf respiratio

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1956.tb02118.x

出版商:Blackwell Publishing Ltd    

年代:1956

数据来源: WILEY

摘要:

The susceptibility of French bean plants to infection by the Rothamsted strain of tobacco necrosis virus as measured by the local‐lesion method is increased by a rise in temperature and usually by darkening the plant before inoculation. If part only of a leaf is darkened, that part becomes more susceptible. Plants in full light also become more susceptible if carbon dioxide is removed from the air, whereas the susceptibility of plants in the dark is not altered.Darkening leaves decreases their content of malic, fumaric, succinic and glycolic acids and increases the content of citric acid; the content of oxalic and malonic acids remains constant. These changes occurred in winter and summer and whether or not darkening increased susceptibility.The effect on susceptibility of individual acids infiltrated into the leaf was measured in leaves kept in the light or in the dark before inoculation. None of the acids used produced any large change in susceptibilit

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1956.tb02119.x

出版商:Blackwell Publishing Ltd    

年代:1956

数据来源: WILEY

摘要:

The ascorbic acid content of leaves of French bean and tobacco depends on age of the leaf and on illumination during the period immediately before harvest. There is a measurable diurnal fluctuation with the French bean. Ascorbic acid is lost within a few days from the leaves of intact plants or from detached leaves cultured in water in darkness, and from the darkened part of partly darkened leaves. The simultaneous increase in susceptibility of darkened leaves to infection by viruses was not reversed by infiltrated ascorbic acid.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1956.tb02120.x

出版商:Blackwell Publishing Ltd    

年代:1956

数据来源: WILEY

摘要:

Replicated trials were carried out in the years 1950, 1951, 1953 and 1954 to see if the spread of leaf‐roll virus and virus Y in potato crops could be reduced by applying insecticides. The crops were disease‐free, except for small numbers of deliberately introduced infected plants, and were sprayed at intervals of 10 or 14 days, according to the stage of growth of the plants, with a tractor‐mounted spraying machine at 1OO gal./acre/application. Disease spread was estimated by growing tubers taken from the five plants on either side of each infector. DDT emulsion, DDT suspension, endrin, schradan, mipafox, malathion, parathion and Systox prevented the spread of leaf‐roll virus and decreased the spread of virus Y, although DDT emulsion was the only insecticide used in all the trials. Dieldrin and toxaphene were ineffective. When virus control was successful, aphid control (estimated by counting apterae in the crops) w

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1956.tb02121.x

出版商:Blackwell Publishing Ltd    

年代:1956

数据来源: WILEY

摘要:

The rate of larval emergence from cysts of the beet eelworm in a variety of aqueous solutions containing organic and inorganic substances is significantly higher than the emergence rate in water. It is suggested that differences between larval emergence rates in monoamino‐monocarboxylic amino‐acids may be related to the lipid solubility of these substances and their ability to penetrate the egg membranes. The larval emergence rate in fructose, glucose, sucrose and maltose was significantly higher than that in water, but in raffinose, arabinose and xylose the rate of emergence was no higher than in water. A high rate of larval emergence occurred in sodium chloride, potassium chloride and mercuric chloride, but not in magnesium chloride or calcium chloride. Experiments with several other organic solutions are described. There is an optimum concentration for larval emergence in beet diffusate. The osmotic pressure of the diffusate when maximum emergence occurred was 0·48 atm. Measurements of shrinkage of unhatched larvae in various concentrations of urea, sodium chloride and sucrose showed that decreasing rates of emergence at higher concentrations may be due to changes in the unhatched larvae brought about: by an osmotic effect. High concentrations of beet diffusate may have a similar ef

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1956.tb02122.x

出版商:Blackwell Publishing Ltd    

年代:1956

数据来源: WILEY

摘要:

Samples of root diffusate from sprouts (Brassica oleraceavar.gemmifera), swedes (B. napusvar.napobrassica), rape kale (B. napusvar.arvmsis), and white mustard (Sinupis alba), all stimulated larval emergence from cysts ofHeterodera cruciferae.When mustard‐root diffusate was added to leachings from the other species tested there was no apparent effect on larval emergence. In half dilution with tap water, mustard leachings were comparable in activity with similar dilutions of leachings from the other species under observation. Leachings from soil were less active than those from the four species of plants tested, but showed significant activity in comparison with tap water.The form of the hatching curve was studied using diffusates from both sprouts and mustard roots, and in each case when cumulative hatch was plotted against time on a logarithmic scale, the sigmoid curve obtained closely fitted the theoretical sigmoid calculated from a probit analysis of the data.Estimates were obtained of the log activity values of leachings from the four species of plants tested and from soil, following an examination of the dilution curves for mustard and sprouts root diffusates. These curves were closely parallel with one another, and it was therefore considered justifiable to derive log activity values for these root diffusates, although the cysts used in the hatching tests and the root‐diffusate samples were each obtained from a single source. For this reason some caution is perhaps called for in the interpretation of the results presented in this pa

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1956.tb02123.x

出版商:Blackwell Publishing Ltd    

年代:1956

数据来源: WILEY

摘要:

Solubilized phenols and cresols, applied at the rate of 1s gal./sq.yd. at 5% strength on light sandy loam, have killed up to approximately half the population of potato‐root eelworm in the top 8 in of soil. When nematicide distribution was aided by rotavation on the same site, yields were approximately doubled compared with untreated areas. The eelworm population in the soil also increased, but not so much as that where no treatment had been applied.Under cold glasshouse conditions on light loam, high‐volume methods have greatly increased the yield of tomatoes compared with untreated plots, but the soil population of potato eelworm has also risen. 20 gal. to the square yard of 0·5%p‐m‐cresol is better than 10 gal. of 1% by both criteria.There is evidence of a slow kill of cyst contents in soil samples stored in the laboratory.The high‐volume type of soil drench is shown to be highly effective under laboratory conditions. The importance of the initial water content of the soil is demonstrated. The superiority of the 20 gal. treatment over the 10 gal. one is confirmed.Investigations on kill in depth by very large applications of dilute nematicide in the same cold glasshouse have demonstrated the part played by the rate at which the material is applied. The degree of kill in the 6–12 in. soil layer is still inadequate.The practical applications of this type of nematicide are brief

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1956.tb02124.x

出版商:Blackwell Publishing Ltd    

年代:1956

数据来源: WILEY

摘要:

Quantitative data are provided for the occurrence ofCalonectria rigidiusculaand other fungi in occluded Mirid lesions and other sites in shoots of cacao plants. Mirid lesions appear to be particularly favourable for the development ofC. rigidiuscula.The fungus also occurs as a saprophyte on cacao pods, and as a wound parasite in woody plants other than cacao; it was successfully introduced into plants of varied affinities by inoculation.C. rigidiusculaspreads from inoculations in cacao stems much more rapidly than other fungi. The results confirm that it is the most important fungus infecting Mirid lesions and causing dieback of cacao in West Africa.Inoculation tests with a range of Amelonado and Trinitario clones suggested that the clones vary in their susceptibility toC. rigidiuscula, but the plant‐to‐plant variation was too great to conclude that any one is highly resistant. Various types of introduced cacao were also tested; preliminary experiments indicate that certain types of Upper Amazon cacao may be resistant, but they need further investigat

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1956.tb02125.x

出版商:Blackwell Publishing Ltd    

年代:1956

数据来源: WILEY

摘要:

An isolate ofVerticillium dahliaeobtained from Uganda was highly virulent to young cotton plants under greenhouse conditions. A hyaline variant which often appeared in culture was as virulent as the parent isolate, but preliminary experiments indicated that it did not survive as long in unsterile soil. The parent isolate grew rapidly in cotton plants after root inoculation and was isolated from stems and leaves well before the appearance of disease symptoms visible to the naked eye.Protopectinase was produced in the absence of pectic materials, but more active preparations were obtained when media contained pectic substances. In general, there was a close correspondence between the protopectinase activity of culture filtrates and the toxicity of these filtrates to parenchymatous cells. Some separation of the two activities was obtained by heating enzyme solutions or by plasmolysing the test tissue.Protopectinase solutions had little pectinesterase activity but rapidly reduced the viscosity of solutions of pectic substances. In general, the properties of protopectinase and the viscosity‐reducing enzyme were similar.Young cotton shoots wilted rapidly when placed in cell‐free filtrates from cultures of the pathogen. Wilting was delayed under conditions unfavourable for transpiration. Evidence was obtained which showed that wilting was caused by the uptake of thermostable compounds of high molecular weight which impeded the upward flow of the vascular sap. Pronounced vascular browning was obtained only when solutions containing protopectinase were used. Wilting and vascular browning were obtained with solutions having little pectinesterase activity; in contrast, a solution having high pectinesterase activity produced relatively little vascular brown

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1956.tb02126.x

出版商:Blackwell Publishing Ltd    

年代:1956

数据来源: WILEY