摘要:

SUMMARYResults of experiments on the pre‐treatment of root tips for freeze‐etching are outlined. Successful freeze‐fixation of viable roots was obtained using seedlings ofAvena, TriticumandZea. The seeds were germinated in contact with water, then placed on top of tubes of filter paper impregnated with glycerol; this allowed aeration of the roots. Most roots grew slightly on exposure to glycerol and remained turgid.AvenaandTriticumgave good freeze‐fixation after 7 days in contact with 20% glycerol and after contact with 20% glycerol for 3 days followed by 25% glycerol for 3 days. Good preservation was also obtained withZeabut results were more variable than inAvenaandTriticum.Root tips fixed in glutaraldehyde, either in glycerol or followed by glycerol, gave consistent freeze‐fixation in all species. Results were comparable to those obtained from viable material. However, in some instances there was shrinkage of the organelles and the plane of fracture within certain membranes wa

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1970.tb02241.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SUMMARYNucleolar morphology in interphase nuclei of non‐growing and growing plant cells has been studied by polarized light and phase‐contrast microscopy. Variation in the optical properties of the nucleoli in unstained preparations are indicative of different morphological stages of this cell organelle with respect to the physiological status of the cells in which these variations occur. A filamentous nucleolar component, the nucleolonema, was evident in unstained nucleoli of explants culturedin vitroand in hypocotyls of germinating seeds. Unstained and stained preparations indicate that the polarized‐light effects observed in nucleoli of previous investigations are primarily associated with this filamentous nucleolar stru

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1970.tb02242.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SUMMARYBy the use of suitable DC micromotors mounted on the specimen stage of the Cambridge Scanning Electron Microscope (SEM), extra degrees of freedom may be imparted to the specimen, thus enabling a more thorough examination of a surface to be carried out. The properties that make an electric motor suitable for use inside the vacuum specimen chamber are discussed. After showing the way in which DC motors have successfully solved two problems in the fibre field, some further applications are proposed.

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1970.tb02243.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SUMMARYMethods for estimating particle‐size distributions in metallurgical structures from the distribution of linear intercepts observed on a metallographic section are extended to include systems in which the particle shape may be modelled by triaxial ellipsoids. Procedures are developed for oriented, partially oriented and randomly oriented systems of particles. Methods for determining the axial ratios appropriate to a given system are outlined for these case

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1970.tb02244.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SUMMARYThe epidermal cells ofEucalyptusleaves are not well preserved by the conventional sectioning methods used for electron microscopy. More satisfactory preservation results from the use of anin vivoperfusion technique using glutaraldehyde or glutaraldehyde‐formaldehyde mixtures. This technique preserves wax on the cuticle surface, rendering it insoluble in the organic solvents used for dehydration and embedding in epoxy resins. Using this method, no direct connection is apparent between leaf wax, cuticle, cell wall and cytoplasm. The Golgi bodies appear to produce vesicles which migrate only in the direction of the outer cell wall, and which might liberate wax precursors into the wall, from where they could diffuse through cuticular lamell to polymerize or oxidize at the leaf surface as waxes of characteristic morpholog

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1970.tb02245.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SUMMARYEmulsion‐developer combinations used regularly in conventional electron micrography yield an approximately linear relationship between density (D) and exposure(E)up to quite high densities (>2.0). This is due to the fact that over the corresponding exposure range the density yield per electron is approximately constant. A practical consequence is that the slope of the D/log10curve, termed the contrast, is a function ofDonly, i.e. it is independent of the emulsion‐developer combination.To achieve higher than normal contrast requires that the density yield per electron should increase with exposure over some exposure range, at least. This effect may be obtained by using what are known commercially as ‘lith’ films and a system of infectious development. The high contrast of such films results from an acceleration of development rate when the developer oxidation products reach a critical concentration.Sensitometric data are presented for electron exposures which show that for average densities of ∼ 1.0 in a micrograph a six‐fold increase of contrast can be obtained with a ‘lith’ system. It is also shown that though the special development effect gives higher granularity than that obtained at the same exposure with a conventional system, the signal/noise ratio is not adversely affected. Practical demonstrations of the effectiveness of the ‘lith’ s

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1970.tb02246.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1970.tb02247.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1970.tb02248.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1970.tb02249.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY