摘要:

SUMMARY.1This investigation proves that lightning is a factor of the first importance in the causation of disease on coconut palm plantations in Malaya.2The “bud‐rot” symptoms occurring in Malayan coconut palm plantations are produced entirely by lightning or the after‐effects thereof. No evidence of the presence of aPhytophthorahas been obtained.3Lightning has been proved to be of some importance in the causation of disease on rubber plantations.4The typical effects on rubber plantations are described, and attention is specially directed to the association of claret‐coloured bark canker at the collar of trees slightly affected by lightning.The writer wishes to acknowledge the considerable help rendered by his colleague, Mr H. Gunnery, in the preparation of photographs and recording of field work. Thanks are also tendered to Mr H. T. A. Biddle‐combe for great assistance in the coconut investigations and to Mr G. Shelton‐Agar for similar assistance in connection with the work on rubbe

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1933.tb07425.x

出版商:Blackwell Publishing Ltd    

年代:1933

数据来源: WILEY

摘要:

SUMMARY.1The yellows disease of tea, the nature of which has hitherto remained obscure, has caused serious losses to planters in Nyasaland.2It is characterised by a progressive degeneration of the bush, in which the leaves become chlorotic, small, uprolled and of stiff texture, and are finally shed. Eventually the bush dies.3The disease usually only appears when the soil has been impoverished by erosion or cropping. On certain soil types it may appear in young plantings on newly cleared land.4In field experiments the disease was prevented or cured by treatment of the soil (a with mixed fertilisers that included sulphates, (b with the sulphates of ammonium, potassium, sodium or magnesium, or (c with elemental sulphur.5Typical symptoms of yellows disease appeared in tea seedlings grown in water culture deprived of sulphur.6Individual branches of diseased bushes in the field made normal healthy growth after absorbing through a side shoot a dilute solution of a sulphate.7The application of sulphates to certain roots only of a diseased bush caused a recovery only in the branches subtended by those roots.8Tobacco plants grown in Nyasaland soil without added sulphur developed a characteristic chlorosis, which was cured by the addition of sulphur.9The part played byKkizoctonia bataticolawas studied and it was concluded that this fungus was not concerned in the initiation of the disease.10This evidence has led us to conclude that tea yellows disease is produced by a deficit of sulphur in the plant in relation to other essential elements.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1933.tb07426.x

出版商:Blackwell Publishing Ltd    

年代:1933

数据来源: WILEY

摘要:

SUMMARY.The development of the chloroplasts inSolatium nodiflorum, S. lycopersicumandNicotiana tabacumis described and comparisons are made with plants infected with aucuba mosaic.In the normal plants after cell division ceases in the meristematic tissue certain minute bodies, which are present in the cytoplasm of all young cells, commence to enlarge. A vacuole is formed in each and this gets bigger as the proplastid increases in size. A starch grain is formed in the vacuole. The outer stroma becomes pigmented and pores are formed in it. Increase in size continues, the mature plastid being about 5/i in diameter. A second or third starch grain may be formed in the vacuole. Chloroplasts sometimes divide.In plants infected with aucuba mosaic certain of the leaf tissues are devoid of plastids and the cells may be undifferentiated. The absence of chlorophyll is brought about by the inhibition by the virus of the development of the plastid primordia. Usually the primordia are destroyed. If plastid development is not prevented in a very early stage, perfectly normal plastids are formed. Mature plastids are never affected by the virus but occasionally intermediate stages may be.Intracellular inclusion bodies are not found in meristematic tissue, but incipient bodies appear when the cells are increasing in size and after plastid development is well advanced. For this reason inclusion bodies are formed indiscriminately in green and chlorotic areas, the virus presumably having reached the green tissues too late to inhibit plastid development.An attempt was made to determine whether the prevalence of intracellular inclusion bodies in tegumentary tissues and their rarity in assimilatory tissues is due to differences in the pH of the tissues but the results obtained were rather indefinite.This work was carried out under the auspices of the Empire Marketing Board.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1933.tb07427.x

出版商:Blackwell Publishing Ltd    

年代:1933

数据来源: WILEY

摘要:

SUMMARY.The precautions which, should be observed in practical application of Holmes's local lesion method in quantitative work with tobacco mosaic have been examined. The aim has been to obtain results with the greatest statistical significance consistent with the use of reasonably small numbers of plants. The adoption of a standard method of inoculation, and the comparison of viruses on opposite halves of the same leaves, were found to be the most important points to observe, and a method of work has been outlined.Tomato spotted wilt forms necrotic primary lesions on the leaves of tobacco of a character suitable for quantitative work, and a number of the results obtained with tobacco mosaic have been checked with this virus.Applications of the method are discussed. It is shown that rapid comparison of virus concentrations from different sources should be possible after further work has been done on dilution curves. An illustration is also given of the application of the method in plotting the curve of “ageing,” or change in virulence with time, of the expressed virus of tomato spotted wilt. This curve was found to be of the logarithmic t

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1933.tb07428.x

出版商:Blackwell Publishing Ltd    

年代:1933

数据来源: WILEY

摘要:

SUMMARY.In this paper the symptoms of aucuba mosaic of tomato in.N. glutinosaare described. A method is discussed whereby it is possible to count the spots formed after inoculation with juice diluted to different strengths. The fact that the number of spots formed is proportional to the amount of dilution is taken as indication of the particulate nature of the virus. A method is suggested for counting the number of virus particles present in a juice. It is shown that the amount of virus present in a juice does not increase after agitation or after treatment with proteolytic enzymes. With trypsin and diastase they were decreased. This decrease, it is suggested, is due to the adsorption rather than to the destruction of the virus. The amount of multiplication of the virus in the tissues ofN. glutinosais examined and compared with the much greater multiplication in tomato tissues.This work was carried out under the auspices of the Empire Marketing Board.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1933.tb07429.x

出版商:Blackwell Publishing Ltd    

年代:1933

数据来源: WILEY

摘要:

SUMMARY.From the necrotic tissues of tomato plants suffering from streak, a virus disease, it is possible regularly to obtain bacteria which belong to one or both of two definite types. The same bacteria are to be found in tobaccos infected with the same disease.If the plants are grown from sterile seed under aseptic conditions throughout and inoculated with bacteriologically sterile virus‐holding streak juice, these bacteria do not appear although the plants develop well‐marked signs of the disease.“No evidence has been found that the bacteria are derived from the virus or the virus from the bac

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1933.tb07430.x

出版商:Blackwell Publishing Ltd    

年代:1933

数据来源: WILEY

摘要:

SUMMARY.A brief account is given of the literature on zone lines in wood, and a preliminary attempt is made to classify the zone lines into groups in order to provide a basis for systematic research and to facilitate the statement of results. A single fungus,X. polymorpha, suspected of causing black lines in hardwoods, is dealt with morphologically and culturally. The development and stromatal production of the fungus on artificial media and wood blocks are described.X. polymorphais established as a black line producing fungus by its production of black lines in inoculated wood blocks. The morphology of the black lines is described in detail and their actual formation has been observed in cotton‐wool. As a result the Suggestion is made that the black lines are the marginal zones of entostro‐mata in the substratum comparable to those occurring in theDiaporthe.The black lines produced by the generaNummularia, Ustulina, HypoxylonandDaldiniain the substratum are stated to be of similar structure and significance.An account is given of aX. polymorphablack line superimposed upon the zone line formed by the attack ofFomes applanatuson beech wood. The confusion existing in the literature on the zone lines ofF. applanatusis partly attributable to this not uncommon phenomenon. The value of zone lines as criteria in the diagnosis of wood rots is discussed and some of the difficulties in the identification of a zone line in a typical rot are pointed

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1933.tb07431.x

出版商:Blackwell Publishing Ltd    

年代:1933

数据来源: WILEY

摘要:

SUMMARY.1Various aspects of the availability of the nitrogen, of fungal tissue to micro‐organisms have been investigated, with particular reference to the influence of the C/N ratio of the material.2Fungal tissue was found to be as suitable a source of nitrogen as ammonium salts and nitrates for the decomposition of straw both by a mixed soil flora and by pure cultures of certain fungi.3The liberation of ammonia in sand culture from fungal tissue by pure cultures of reputedly active ammonifiers was measured.4The nitrification in soils of a number of samples of fungus tissue was compared with that of artificial mixtures of equal C/N ratio built up from glucose, cellulose and straw, each with added inorganic nitrogen.5A very clear correlation was found between the C/N ratio of the fungal material and the nitrogen nitrified. In one series in hill‐side soil nitrification increased from 42 to 80 per cent, in 6 months as the ratio decreased from 15.8 to 5.5; in another, from 20 to 75 per cent, as the ratio decreased from 17 to 7.6No evidence was found for the existence of a very resistant and unnitrifiable residue from fungal tissue as claimed by some workers, and incomplete nitrification is probably due to the attainment of biological equilibrium or of a state in which change is very s

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1933.tb07432.x

出版商:Blackwell Publishing Ltd    

年代:1933

数据来源: WILEY

摘要:

SUMMARY.1An extensive review of the literature on nitrification shows that the workers in this subject may be divided into three groups, viz. (a the Winogradsky or purely autotrophic group, (b those who include growth in organic media, (c those who exclude autotrophic growth.1The process of nitrification in soils and filter beds is essentially the same and the organisms concerned exhibit the same cultural characteristics, viz. autotrophic growth in purely mineral solution containing carbonates and low thermal death‐point (56° C).1In the absence of carbonates heterotrophic organisms can supply the necessary carbon, dioxide by the decomposition of organic matter, a process which accounts for nitrification in acid soils and filter beds. In the absence of a salifiable base the oxidation of ammonia is arrested by the formation of free acid and at apH of 5.5 the nitrous acid is spontaneously oxidised to nitric acid.1The inhibitive action of organic matter on nitrification can be accounted for by accumulation of carbon dioxide and ammonia and deficient aeration. Removal of any of these factors results in increased nitrification.1Increased nitrifying power of soil after passage through earthworms is recorded and accounted for.1The restrictive influence of Winogradsky's ideas on autotrophism ara discussed, and the possibility of nitrifying bacteria being a phase in the life cycle of heterotrophic organisms is suggest

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1933.tb07433.x

出版商:Blackwell Publishing Ltd    

年代:1933

数据来源: WILEY

摘要:

SUMMARY.The life history of the clover‐seed midge has been studied, and methods of control are discussed. The midge destroying clover seed in England isDasyneura leguminicolaLint., the species common in the United States. It is typically two brooded and the second brood overwinters in the larval state. There are four larval instars.An attempt was made to establish the immunity of a variety of red clover, but all the varieties used were susceptible to attack. White clover was not attacked. It is suggested that unless an immune variety can be produced, clovers grown for seed production should be chosen with a view to their being in the green‐head either before or after the time of maximum emergence of the midges (e.g.the week from May 28th to June 4th in Harpenden). Furthermore, if cutting of the first crop is used as a means for destruction of the second brood of midges, this should take place within 10 days of the crest of emergence of the midges, the farmer deriving what information he requires from the advisory entomologist of his particular distr

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1933.tb07434.x

出版商:Blackwell Publishing Ltd    

年代:1933

数据来源: WILEY