摘要:

Only plants in the natural order Tiliales were susceptible to experimental infection by viruses found infecting cacao. Of sixty‐three species in the Tiliales colonized with infective mealybugs, twenty‐eight became infected with the New Juaben virus. The ease with which different species contracted infection and the severity of symptoms varied considerably. The host ranges of seven other viruses were all contained in that of the New Juaben virus. The viruses could be divided into three groups according to their host ranges, and it is suggested that host ranges may prove helpful in attempts to classify cacao viruses. Four species ofCorchoruswere all rapidly killed by any of the eight viru

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1958.tb02170.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

摘要:

Although the five cacao viruses studied produce different external symptoms in infected plants, they affect internal anatomy similarly. Symptoms on leaves occur only if these are still developing when they become infected, and the viruses seem to produce their effects usually by preventing differentiation of the cells. The tissues of chlorotic areas of infected leaves are undifferentiated and similar in structure to young unexpanded leaves. In stem and root swellings xylem and phloem are both increased, but they occur in the same proportions as in normal secondary thickening. The anatomical effects of infection seem insufficient alone to account for the death of cacao trees, but they may well be complementary to the serious necrosis of the root system which results from virus infections.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1958.tb02171.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

摘要:

Although cultures of normal and conditioned tobacco callus tissue occasionally became infected when dilute solutions of tobacco mosaic virus was poured over them, injuries were usually required, and the number of infections depended on the type and number of injuries. Tissues infected by superficial injuries usually became virus‐free after subculturing, whereas those infected by needle‐prick remained infected permanently. Although no plasmodesmata were found joining cells in the tissue cultures, tobacco mosaic virus moved between them at a rate of about 1 mm. per week, approximately the same rate as it moves through cells of the leaf parench

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1958.tb02172.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

摘要:

Virus‐infectedAdansonia digitataL. were found in the Guinea‐savannah woodland forming the Northern Territories and on the Accra plains of Ghana, but those tested in the rain forest were not infected. Three viruses isolated from infected trees resembled the Kpeve cacao virus, but no definite relationship could be established. It is unlikely that the original outbreaks of swollen shoot in cacao came fromA. digit

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1958.tb02173.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

摘要:

The possibility of using an embryo test as a means of determining the reaction of wheat varieties to loose smut (Ustilago tritici(Pers.) Rostr.) has been investigated. Fifty‐seven varieties were inoculated with two physiologic races by the partial vacuum method and the embryos, seedlings, and adult plants were examined for infection. Most of the varieties were fully susceptible to one or both races, and only ten showed real resistance to any one race. Braun R and Molinel proved almost immune to infection. The resistance in other varieties which showed no infection in the field was expressed as embryo susceptibility, i.e. the embryo became infected in much the same way as in field‐susceptible varieties.In the latter varieties infection passes from the embryo into the growing point of the young seedling. In the embryo‐susceptible field‐resistant varieties, infection does not pass from the scutellum and the growing point is therefore uninfected.The reaction of most of the varieties tested was straightforward resistance or susceptibility, but in a few varieties a small proportion of the grains reacted differently from the majority. These reactions are di

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1958.tb02174.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

摘要:

Limited systemic protection of broad bean againstBotrytis fabaeand of cucumber againstCladosporium cucumerinumhas been observed as a result of the application of pyridine‐2‐thiol‐N‐oxide and its carboxymethyl derivative. Apparently this protection is, to some extent, the result of translocation of the chemicals in the plants. It was found that the vapour phase of pyridine‐2‐thiol‐N‐oxide plays an additional role in the chemotherapeutic activity. There is no evidence that the copper chelate of pyridine‐2‐thiol‐N‐oxide is translocatable in plants. Root applications of these three compounds had no

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1958.tb02175.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

摘要:

The slopes of the lines relating probit mortality to the log.‐dose of DDT are generally lower for resistant than for susceptible strains of houseflies. Two effects that could each account for this are discussed. The first concerns the relation of the amount of DDT absorbed to the dose; the conditions under which it would occur are stated, and published data on the absorption are analysed. The second concerns the variability from fly to fly of the amount of DDT exerting a toxic effect at the primary site of action, a variability that would seem to be brought about, or greatly intensified, by the enzymatic detoxification of DDT in resistant flies. Both mechanisms may occur, reinforcing one anothe

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1958.tb02176.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

摘要:

An apparatus for determining the repellency of a chemical compound is described. Its action depends upon the insects' coming into contact with the compound deposited on a glass surface. The numbers of insects settling on treated and untreated glass plates at intervals over a period of 40 min. and under conditions that minimize varying disturbing factors are counted. The quotient obtained by dividing the total numbers on the untreated plates by the total numbers on the treated plates is called the ‘repellence quotient’, and must reach certain given values before significance is assumed and a compound is regarded as repellent.Typical results obtained with the apparatus are given and include the detailed determination of the repellency of butoxypolypropylene glycol (MW 8

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1958.tb02177.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

摘要:

Two preparations of the hind‐leg of the locust have been used to investigate the physiological effect of chemicals on nerve muscle and on the central nervous system.In the first preparation, the isolated hind‐leg is made to kick regularly by electrical stimulation of the crural nerve. Test chemicals are perfused in saline solution through the femur.The second preparation makes use of a reflex synapsing in the metathoracic ganglion. A reflex retraction of the tibia of the hind‐leg is initiated by stimulating the tarsus by heat at regular intervals; the chemicals are applied in agar or paraffin blocks directly to the ganglion. In both cases the movements of the tibia or of the extensor or flexor tibialis muscles separately are recorded mechanically on a smoked drum.Acetylcholine has no action on the nervous system except for an unusual action on the nerve muscle preparation. Acetyl β‐methylcholine, carbamylcholine and benzoylcholine have no action on either preparation except at high concentration.Decamethonium andd‐tubocurarine had no effect on either preparation, while nicotine and eserine, after initial excitation, caused a simple reversible block in both preparations, the ganglion being affected at a lower concentration.Adrenalin and adrenergic drugs have no effect on either preparation.The organo‐phosphorus insecticides, parathion, paraoxon and TEPP, acted on the ganglion only and at low concentrations. Their main site of action is on the central nervous system.DDT affected ganglionic and nerve muscle preparations, whereas γ‐BHC acted rather similarly on the ganglion but had no effect on nerve muscle.There is no evidence for a cholinergic mechanism at the neuromuscular junction in the leg muscles. The ganglion, on the other hand, was markedly affected by the anticholinesterases tested, but acetylcholine and related cholinesterase substrates, and drugs which interfere with the action of acetylcholine in mammals, had no effect. Acetylcholine was still without effect when injected through the membrane sheathing the ganglion. On the other hand, micro injection experiments show that the sheath is relatively impermeable

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1958.tb02178.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

摘要:

Experiments on vertical migration through saturated soil fractions, horizontal migration through soil fractions at different pressure deficiencies and migration in single layers of particles showed that the beet eelworm,Heterodera schachtiiSchmidt, attained maximum speed when the pore diameters were between 30–60 μ. Speed of the eelworms increased as lateral displacement of the body was restricted by external resistances acting perpendicularly to the body axis; at the maximum speed there was no lateral movement, each part of the body following the part immediately in front of it. The speed of beet eelworm larvae in water films of various thickness was measured; maximum speed occurred in a film 2–5 μ thick. Four arbitrarily classified types of progression were observed in the pore spaces. It is suggested that the ‘moisture characteristic’ supplies most of the information required about the physical properties of the soil in relation to eelworm movement. By examining such a curve the pore size distribution can be ascertained and the probable behaviour of beet eelworm larvae in the medium

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1958.tb02179.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY