摘要:

In carrot explants infected with aster yellows, mycoplasma-like bodies (MLBs) were seen only in the phloem of the primary cultures. During subsequent transfers of the cultures, MLBs underwent gradual degeneration and disappeared within 80 days. Electron microscopy showed three stages of degeneration. In the first stage, which started after about 30 days in culture, MLBs changed from a round to a filamentous shape and became electron opaque. During the second stage, the MLB membrane ruptured, and numerous unusual structures were observed. In the final stage, the MLB particles disrupted and the cells plasmolysed. Differentiation occurred earlier in infected than in healthy cultures, and the new phloem tissue contained no MLBs.

ISSN:0008-4026    

DOI:10.1139/b78-016

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Dormant long-shoot buds were harvested from two 45-year-old trees ofPinus resinosa. The shoot apices were examined for variation in shape, size, and histochemical staining in relation to their position in the crown. On nonshaded branches from the exposed south side of the trees there were no significant differences in size and shape of shoot apices associated with height in the crown. However, on the north side of the tree there was a marked increase in height and height–diameter ratio, and a decrease in diameter of shoot apices from branches below the point where the canopy closed and branches were subject to continual shading. Within the shaded portion of the crown, there were no significant differences in the size and shape of the apices studied. Megasporangiate strobili primordia were found in buds with terminal shoot apices having a low height–diameter ratio (<0.400), whereas microsporangiate strobili primordia were found in buds with terminal shoot apices having a relatively high height–diameter ratio (>0.400). Staining intensity for total carbohydrates, total proteins, and RNA decreased with decreasing height in the crown. There were no great differences in stain intensity between shoot apices from sun and shade branches from the same whorl. Therefore, the potential of a branch appears to be related to the size of the shoot apex which is correlated with its exposure within the crown.

ISSN:0008-4026    

DOI:10.1139/b78-017

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Two deposition sites for silicon, both perivascular, were detected by electron-probe microassay in rhizomes of field specimens ofAndropogon gerardiiVitman andA. scopariusMichx. (i) Si was confined, in both species, to several layers of cells immediately outside the stele, occurring therein as silica aggregates restricted to the inner tangential walls (ITW). These Si-accumulating cells exhibited similarities in position, shape, and wall thickness, as well as silica deposits, to root endodermal cells of the same species. (ii)InA. gerardiionly, Si was deposited additionally in the central region of the stele, on the ITW of sheath cells surrounding the larger vascular bundles.A comparison of the silica aggregates of the rhizomes in terms of distribution, morphology, and X-ray intensity is made between the twoAndropogonspecies, as well as of the corresponding root deposits. These aggregates may be of significance in aiding the retention of water and solutes within the rhizome.

ISSN:0008-4026    

DOI:10.1139/b78-018

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The growth regulators abscisic acid (ABA), phaseic acid, dihydrophaseic acid, and 3-indolylacetic acid (IAA) have been detected and the levels were measured in extracts of leaves fromSorghum bicolorusing high performance liquid chromatography (HPLC). For purification of extracts, columns contained 37- to 75-μm-diameter octadecylsilica. For analysis of the growth regulators, microoctadecylsilica columns were used. Both columns were used in the reverse phase mode. The efficiency and resolution of the microcolumn combined with the high sensitivity of the ultraviolet absorption microcell detector could accurately determine as little as 2 ng of ABA and 6 ng of IAA. The method is suitable for routine analysis of levels of regulators in moderately large numbers of plant extracts.

ISSN:0008-4026    

DOI:10.1139/b78-019

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

When vegetation data are summarized on the basis of some method of ordination, a search for distinct groups or trends is greatly facilitated if the cloud of sample points is viewed under a lens stereoscope in three dimensions. The present paper describes a simple method to construct stereograms and illustrates their application in a classification problem.A stereogram is composed of two images of a three-dimensional object. The left image and the right correspond respectively to sightings with the left eye or the right eye of the observer. The diagrams are placed side by side at a specified distance apart, and when viewed with the aid of a stereoscope, the images will merge resulting in a three-dimensional picture.

ISSN:0008-4026    

DOI:10.1139/b78-020

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Plants ofCelosia cristataL. are removed from an 8- to a 16-h photoperiod or from a 16- to an 8-h photoperiod after 20 or 30 days of culture. The percentages of fasciated stems and of reproductive meristems observed at the 70th day of culture are calculated for control and removed plants. Thus, it is shown that there is an important phase in the plant ontogenesis. This phase corresponds to a new proliferating activity of thecorpuson day lengths of 16 h and 8 h.

ISSN:0008-4026    

DOI:10.1139/b78-021

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The autecology of the estuarine alga,Blidingia minimavar.subsalsa(Kjellman) Scagel (Chlorophyceae) was considered with regard to its distribution and abundance in the Squamish River estuary, British Columbia, Canada, by integrating a multifactorial laboratory study and field data.Increases in abundance ofBlidingiawere associated with brackish waters, high light intensity, high air temperature, moderate desiccation, and possibly, favourable ion ratios. The upper limit of vertical distribution appeared to be associated with unfavourable osmotic conditions, e.g., heavy rain or extreme desiccation, and the lower limit with low light intensities. Horizontal distribution was limited by absence of seawater on the freshwater side and high salinities on the marine side.The periods of highest and lowest field abundance ofBlidingiacompared favourably with the laboratory combinations which produced the highest (20‰, 20 °C, 50 μg-at ℓ−1N and 5.0 μg-at ℓ−1P) and the lowest photosynthetic rates (0.25‰, 5 °C at all N and P concentrations) respectiv

ISSN:0008-4026    

DOI:10.1139/b78-022

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Magnaporthe griseais proposed as a comb.nov. forCeratosphaeria griseaHébert, the perfect state ofPyricularia grisea(Cke.) Sacc.Pyricularia griseais very close morphologically toP. oryzaeCav., well known as the causal agent of blast disease on rice.Magnaporthewas recently established in the Diaporthales to accommodate a single species,M. salvinii(Catt.) Krause & Webster, which was described as the cause of stem rot of rice with conidial state known asNakataea sigmoideaHara. Based on a review of the taxonomic characters ofCeratosphaeria grisea, the desirability is discussed of its inclusion in the genusMagnaporthe.

ISSN:0008-4026    

DOI:10.1139/b78-023

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

A number of nomenclatural changes were required for the presentation of the descriptive resource inventory of vascular plants of British Columbia. Documentation and discussion of these changes are presented. Additional notes and discussion are provided for some taxa presenting unusual problems in the British Columbia vascular plant flora, and several new taxa are described.

ISSN:0008-4026    

DOI:10.1139/b78-024

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The transverse relaxation rate of water protons of nonacclimatedHedera helixL. cv. Thorndale (ivy) bark decreased in the presence of added extracellular Ca2+, Mg2+, or CO2. Evidence that the decreased transverse relaxation rate is due to decreased plasmalemma water permeability is presented. The decrease in plasmalemma water permeability induced by Ca2+and CO2was less in cold-acclimated ivy bark than in nonacclimated ivy bark, indicating that the process of cold acclimation altered a functional property of the plasmalemma. It is not known if the functional change in the plasmalemma is related to the degree of plant cold hardiness or is simply a low temperature response.

ISSN:0008-4026    

DOI:10.1139/b78-025

出版商:NRC Research Press    

年代:1978

数据来源: NRC