摘要:

Summary.Tomato spotted wilt inoculum stirred in the process of inoculation lost its virulence more rapidly than inoculum standing undisturbed.The rate of inactivation of the virus was increased by bubbling air through the inoculum.When all but traces of free oxygen were excluded by bubbling nitrogen through the inoculum loss of virulence was slightly delayed but the final rate of inactivation was practically unchanged.The addition of two oxidising agents, chloramine T and hydrogen peroxide, increased the rate of inactivation.Of six reducing agents tested, one, sodium sulphite, retarded inactivation very markedly. In one experiment at a temperature of 22° C. the virus remained active for more than 36 hours in a 0.2 per cent, solution of the anhydrous salt while control inoculum prepared at, the same time with distilled water was completely inactivated in less than 5 hours.Sodium nitrite retarded inactivation slightly.The remaining four reducing agents—ferrous sulphate, tannic acid, hydroquinone and cysteine hydrochloride—hastened inactivation, but the oxidation‐reduction potentials existing in the virus‐containing systems were not known.These results are briefly discussed in their bearing on the possibility that the normal rapid inactivation of spotted wilt virus which occurs in the standing juice is due to an oxidation

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1934.tb06898.x

出版商:Blackwell Publishing Ltd    

年代:1934

数据来源: WILEY

摘要:

Summary.Experiments on the movement of the virus of aucuba or yellow mosaic of the tomato in the host plant are described. It has been found that the presence of the virus in the tissues is not always associated with symptoms, and that the symptoms appear in those tissues which have developed after infection. It was also found that the distribution of the virus throughout the plant was not uniform. In the chlorotic tissues the virus content was higher than in the neighbouring green areas.A large series of experiments has been carried out on the transmission of six different viruses in the seed of tomato or tobacco. In no instance was there any evidence of transmission, and it is suggested that the chance of seed transmission of these viruses is very slight.The movement of the virus from an infected leaf and the possibility of its being carried with the food material were examined, and results are given which show that the virus can move independently of the food materials and that, under certain conditions, the virus apparently moves in the direction opposite to that of the metabolites.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1934.tb06899.x

出版商:Blackwell Publishing Ltd    

年代:1934

数据来源: WILEY

摘要:

Summary.The literature dealing with the effect of virus diseases on the metabolism of the host plants is briefly summarised. Results are presented of work which has been carried out on the aucuba or yellow mosaic in tomato. The effect of time of inoculation has been studied in some detail. It has been found that the plant is generally reduced by the disease, and that the carbohydrate and dry‐matter content of the diseased plants is less than that of the controls. The stage of development of the plant is not apparently affected by the disease; the diseased plants, though reduced in size, have the same number of leaves and flower trusses as the controls. The nitrogen content is not materially affected by the disease. The effect of the disease on the respiratory mechanism of the host tissues has been examined, and it has been established that the CO2, output of these tissues is higher than that of the controls. This is found when the output is expressed in mg. of CO2, per three‐hour period in terms of the initial fresh weight, the residual dry‐matter content or of the residual nitrogen content. The higher CO2, output is also found ill respiration in oxygen or in nitrogen. This has been attributed to all increase in the efficiency of the enzyme system of the diseased p

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1934.tb06900.x

出版商:Blackwell Publishing Ltd    

年代:1934

数据来源: WILEY

摘要:

Summary.1. The effect of soaking in water on the subsequent germination of several species of Gramineae has been determined under a variety of conditions.2. With most species an acceleration of germination results from presoaking, but this may be negligibly small under optimum conditions in the soil.3. Dryness of soil and a relatively low temperature greatly increase the differentiation between the germination of soaked and untreated seeds. A peculiarly extreme case of such an effect by the second of these factors is provided byPhleum pratense.4. It is not possible to generalise regarding the behaviour of different species in relation to soaking in water. Closely related species (e.g. Lolium iatalicumandL. perenne, andFestuca pratensisandF. elatior) show considerable differences of behaviour.5. In none of the species examined is the acceleration produced by soaking so pronounced as is the case inDactylis glomerata.6. The acceleration which results from presoaking inAvena sativais brought about by the start given to the early processes of germination.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1934.tb06901.x

出版商:Blackwell Publishing Ltd    

年代:1934

数据来源: WILEY

摘要:

Summary.1. The disease symptoms generally grouped in England under the designation “spraing or internal rust spot” hare been segregated into two types, namely “arc” lesions constituting spraing disease and “blotch” lesions constituting internal rust spot disease.2. Isolation experiments have been carried out to see if either of the organisms reputed to be the cause of these tuber necroses (B. solaniolensandB. rubefaciens) were constantly present in the lesions. The results show that neither organism occurs in spraing, but that there is some slight evidence that bacteria may be concerned in the production of internal rust spot.3. Inoculation experiments have been carried out withB. solaniolensandB. rubefaciens. No infection has been produced byB. solaniolens, and though some slight evidence of infection withB. rubefacienshas been obtained the results are far from convincing.4. Spraing has been transmitted by tuber grafting in three cases out of eighteen, so that the results of Atanasoff have to that extent been confirmed. Spraing was also transmitted in one instance by a ground‐up suspension of the arc lesions. This evidence, together with the absence of any constantly occurring bacterial organism in the lesions, inclines the writer to support Quanjer's view of the virus origin of spraing. Internal rust spot could not be transmitted by tuber grafting. The fact that organisms are more constantly present in the lesions, thatB. rubefaciensapparently produced internal rust spot in one experiment, and the failure to transmit this disease by grafting suggest that internal rust spot is a distinct disease from spraing, and may possibly be bacterial in origin.6. Attempts to isolate a possible infectious principle by leaching from soil after having buffered soil suspensions to differentpH values have so far led

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1934.tb06902.x

出版商:Blackwell Publishing Ltd    

年代:1934

数据来源: WILEY

摘要:

Summary.1. The three elements commonly applied in the form of mineral fertilisers in farm practice did not produce rapid decomposition of filter paper cellulose in incubated cultures, whereas the addition of all “essential” elements produced rapid decomposition.2. Fungi appeared to be more important than bacteria in the decomposition of the filter paper cellulose.3. The numbers of ammonifying bacteria in cellulose fermentation cultures increased with each additional “essential” element or group of “essential” elements.4. Different horizons or layers of the Alberta peats studied differ greatly in colour or stage of decomposition and in reaction orpH value.5. The surface samples of peat usually contain less ash than the deeper samples.6. The nitrogen content of the different samples varies rather widely, and the subsurface layer usually contains about twice as much nitrogen as the surface layer.7. The total phosphorus content of the different samples does not vary as much as the nitrogen content.8. The calcium oxide percentages and thepH values indicate that the Carnwood and Spruce Grove peats require liming and that the Winter burn and Stonyplain peats do not require liming for satisfactory crop production.9. The cellulose content of the peats varies from none to about 47 per cent. of ash‐free cellulose, and the lignin from about 20 to 49 per cent. A decrease in cellulose content is usually accompanied by an increase in lignin.10. Cellulose, lignin, and ash together nearly always make up about two‐thirds or more of the weight of the peat. Nitrogeneous organic matter would account for about 3–16 per cent., and petroleum‐ether‐soluble material for only 1 per cent. or less of the total peat.11. Growth of oat seedlings and bacterial plate counts indicated that the fertility of Carnwood surface peat was not greatly increased or affected by the addition (about three to four months earlier) of ordinary applications of fertiliser salts.12. At the end of an incubation period of 50 days appreciable losses of cellulose had occurred in the Carnwood peat cultures to which an abundant supply of fertiliser salts had been added; and bacterial numbers were increased by the addition of fertiliser salts. In the case of the Winterburn peat the losses of cellulose, if any, were within the experimental error of the determination.13. After nineteen days' incubation at a relatively high temperature (55°C.) all of the cultures of Spruce Grove peat showed loss of cellulose, the largest loss occurring in the culture to which lime was given in addition to an abundant supply of th

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1934.tb06903.x

出版商:Blackwell Publishing Ltd    

年代:1934

数据来源: WILEY

摘要:

Summary.1. Early writings indicate that attack by sheep blowflies was common and well known in the early sixteenth century, prior to the establishment of sheep farming in North Wales.2. A survey of North Wales has shown thatLucilia sericataMg. isthesheep blowfly of the province. In two advanced cases only were larvae ofCalliphora erythrocephalaMg. present, and then only in small numbers.3. Sheep are attacked from May until October. The degree of attack as indicated in a summary of seasons regarded as severe was as follows:Upland districts—10–15 per cent. of sheep attacked;Lowland districts exposed—20–25 per cent.;Lowland wooded—35–40 per cent.4. The complete absence of parasitism among larvae taken fromlivingsheep was a signscant result of the survey. Such a source of unparasitised larvae will mitigate success in the biological control of blowflies.5. The life history ofLucilia sericataunder North Wales conditions has been investigated. Four generations are recorded. The normal mode of hibernation is in the prepupal stage, which hibernates in late September or October and returns to the soil surface from mid‐March onwards, when the soil temperature at 8 in. approaches 45° F. and when in the upper layers is slightly higher.6. Shepherds, normally, “rub out” larvae from infested sheep, assuming that starvation and death results in the soil. Over 90 per cent, of such larvae produced imagines, and such infestations are pure cultures ofLucilia sericataMg. with an absence of competitive secondary species. Experiments, combined with a morphological study, showed that at the temperature of the sheep's body, larvae attain the third instar in 24 hours. They are then only half‐size, but can successfully produce imagines despite subsequent starvation. The present practice, therefore, should be changed, and a larvicide applied before the larvae are removed from the wool.7. There is clear evidence of the greater susceptibility of lambs to attack, and the factors involved are being studied.8. Observations have been made on the relative susceptibility to attack of six different breeds of sheep and their crosses. The degree of attack ranged from the Wiltshire breed, which is only rarely attacked, to the Southdown breed, which is frequently subject t

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1934.tb06904.x

出版商:Blackwell Publishing Ltd    

年代:1934

数据来源: WILEY

摘要:

Summary.1. A comparative study has been made during 1928–1933 of the aphis infestation atsuccessfulseed potato producing centres, where there has been no increase in virus infection among the stocks, and also atunsuccessfulcentres, where the increase in virus infection has been large and rapid.2. The technique developed for this study—one which is applicable for an aphis survey of prospective seed potato producing areas—is given. Identification, in the field, of the different species of aphides infesting potato is desirable in such a survey, and descriptions, with photographs, are presented.3. Ecological notes on the development of the aphis infestation show thatM. persicae—the species that is generally responsible for the spread of virus diseases among potatoes—hibernates as apterae in considerable quantity on winter Brassicae, particularly savoys. These plants constitute the main source of alate spring migrants in most rural districts. The main migration of alatae takes place, normally, in early June, and, in North Wales, is largely from the east. Alatae are not common during July and August and do not increase until the late September migration from potatoes.4. The index figure of infestation at centres in which there was a rapid increase in virus diseases among the potato stocks always exceeded 100M. persicaeper 100 leaves, and attained such numbers as 1000 individuals per 100 leaves. At centres where there has been no increase in virus infection, the index figure of infestation has not exceeded 20M. persicaeper 100 leaves. The period at which this index figure should be obtained is important, and, with certain exceptions, mid‐July proved to be the most satisfactory. It is essential that the figure should be an index of the intensity of the initial infestation of alatae fromoutsideBources and their subsequent spread, and should not be simply an index of the rate of reproduction of aphideswith

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1934.tb06905.x

出版商:Blackwell Publishing Ltd    

年代:1934

数据来源: WILEY

摘要:

Summary.1. An extensive investigation of the Pigmy Mangold Beetle (Atomaria linearisSteph.) on sugar beet and mangold has been made during the past six years, both in the field and in the laboratory2. The symptoms of attack are given, together with a brief account of the distribution and life history of the beetle.3. General field observations of infested areas both in Lincolnshire and Shropshire indicate that epidemics of the Pigmy Mangold Beetle in sugar‐beet and mangold crops only occur under certain conditions, of which continuous cropping of the land with susceptible plants is usually considered of primary importance.4. It is found that environmental factors have a marked influence on the relative susceptibility of sugar‐beet and mangold crops to serious injury by the beetle. Evidence is produced to show that many of these factors are under the direct command of the grower and their significance on control measures discussed.5. Field experiments on control of the pest show that, of the treatments tested, the use of phenol and magnesium sulphate at the rate of 1 and 5 per cent. respectively, as a seed steep is the most effective.6. There is reason to believe that the common practice on the Continent and in certain districts in this country of sowing crude naphthalene with sugar beet seed as a deterrent against the Pigmy Mangold Beetle results in serious damage to germination.7. Different varieties of sugar beet vary in the degree to which they are liable to infestation but the differences are generally small and unimportant. Mangolds, as a rule, are more resistant than sugar beet.8. In addition to mangold and sugar beet, the beetle is recorded for the first time in Great Britain on garden beet and White Goosefoot (Chenopodium album). Some evidence is presented to show that a rotation of crops as means of control of the beetle may be ineffective in areas where White Goosefoot preva

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1934.tb06906.x

出版商:Blackwell Publishing Ltd    

年代:1934

数据来源: WILEY

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1934.tb06908.x

出版商:Blackwell Publishing Ltd    

年代:1934

数据来源: WILEY