摘要:

The mature embryo sac of wheat contains an egg apparatus composed of an egg cell and two synergids at the micropylar end, a central cell with two large polar nuclei in the middle, and a mass of 20 to 30 antipodals at the chalazal end. A comparison was made of the ultrastructural features of the various cells of the embryo sac. The features included the position of the nucleus and vacuoles, the number, structure, and distribution of organelles, and the extent of the cell walls surrounding each cell. The pollen tube enters one synergid through the filiform apparatus from the micropyle. The penetration and discharge of the pollen tube causes the further degeneration of that synergid, which had already undergone changes before pollination. The second synergid does not change further in appearance following the penetration of the first by the pollen-altered tube. Half an hour after pollination at 20–25 °C, two male nuclei are seen in the cytoplasm of the egg and the central cell. At about 1 h after pollination, one sperm has made contact with the egg nucleus, while the other sperm is fusing with one of the polar nuclei.

ISSN:0008-4026    

DOI:10.1139/b85-019

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Twenty-one strains ofFusarium oxysporumwere classified on the basis of vegetative compatibility or the ability to form hetcrokaryons. Heterokaryon formation was demonstrated by pairing mutants that were unable to reduce nitrate. These "nitmutants" could be recovered without mutagen treatment from selective media containing KClO3. On Czapek's minimal medium thenitmutants had a radial growth rate like that of wild type, but their colonies were very thin. Two genetically differentnitmutants were recovered in each of the 21 strains and paired in all combinations on minimal medium. Heterokaryon formation was indicated by dense growth where the two mutant colonies touched. As a result, 16 vegetative compatibility groups (VCGs) were defined such that only strains in the same VCG were vegetatively compatible. In no case was a strain assignable to more than one VCG. There was some evidence for a correlation between VCG and forma specialis. An evolutionary model to explain this correlation is proposed. Vegetative compatibility may be a fast and easy way to distinguish pathotypes ofF.oxysporum.

ISSN:0008-4026    

DOI:10.1139/b85-020

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

A new experimental procedure was developed to produce samples of leek roots containing early stages in colonization by vesicular–arbuscular mycorrhizal (VAM) fungi. This procedure involved transplanting leek seedlings into a pot culture containing an established symbiosis. Abundant colonization of seedling roots occurred in 1 week. Samples harvested at 2-day intervals after exposure to the inoculum were used to determine the time course of colonization. Contact of the root by external hyphae occurred after approximately 1 day, followed by penetration of hyphae into the root at about 2 days, arbuscule formation within 3–4 days, and vesicle formation after 4–5 days. The average distance from growing root apices at which each of the above events first occurred and the growth rate of intercellular hyphae were also estimated. Stages in root colonization were then documented using the chlorazol black E staining procedure. This transplant procedure should allow the production of abundant material at early stages in VAM development for chemical and morphological investigations as well as provide an efficient inoculation procedure.

ISSN:0008-4026    

DOI:10.1139/b85-021

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Conidiogenesis and conidial morphology in twoPseudospiropesspecies, anamorphs of two unnamedStrossmayeriaspecies, were studied using light microscopy and scanning electron microscopy, and for one of these, transmission electron microscopy. Conidiogenesis is clearly holoblastic. In these species there are approximately 10 cells per conidium, the apical and basal ones being darker than the others. A gel surrounds the conidium, and what probably is a gelatinous appendage is seen at its apex. The conidial wall is composed of at least eight layers, the exterior surface being distinctly poroid. There are columnar irregularities in the conidial walls. These morphological features have potential taxonomic importance.

ISSN:0008-4026    

DOI:10.1139/b85-022

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Five xylem oleoresin monoterpenes and 17 morphological characters of trees in four pine stands in Alberta were measured to delineate pure lodgepole pine (Pinus contortaDougl. var.latifoliaEngelm.) from jack pine (P.banksianaLamb.) in a region where hybridization commonly has been reported. Multivariate analysis determined α-pinene, β-phellandrene, and needle length best separated the taxa. The monoterpene composition of two putative hybrid stands at Onoway and Devon closely resembled that of jack pine. Analysis of the four major monoterpenes in an additional 10 stands allowed the identification of a transition zone between jack pine and lodgepole pine stands, which occurred farther west than previously reported and contained stands of highly variable monoterpene types. Trees in this region morphologically resembled lodgepole pine. The presence of variant monoterpene types in Front Range lodgepole pine stands and their absence from the Cypress Hills provide evidence for introgression of jack pine into lodgepole pine. No evidence of gene flow from lodgepole pine to jack pine was found. The two putative hybrid stands at Onoway and Devon probably consisted mostly of jack pine, with a small complement of hybrids.

ISSN:0008-4026    

DOI:10.1139/b85-023

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Descriptions and illustrations are given for 12 species ofDiheterosporarecovered from parasitized rotifers in Ontario. Four of these species have been previously described and eight are described for the first time.

ISSN:0008-4026    

DOI:10.1139/b85-024

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

A new taxon,Betula murrayana, is described from southeastern Michigan. This birch appears to be an oetoploid (2n = 112) derivative of an unreduced gamete of Purpus birch (B. ×purpusiiSchneid. =B.alleghaniensisBritt. ×B.pumilaL., 2n = 70) and a reduced gamete of yellow birch (B.alleghaniensis, 2n = 84).Betula murrayanahas relatively uniform, good, large pollen grains and leaf stomata larger than its putative ancestors; this multistemmed plant has larger leaves and fruits than the hybrid.

ISSN:0008-4026    

DOI:10.1139/b85-025

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Twenty-eight chromosome number determinations inFestuca rubraL.s.l. from eastern Québec show the occurrence of both hexaploids (n = 21) and octoploids (n = 28). Some characters distinguish both cytotypes, but they can be modified by cultivation. All the octoploids are identified asF.diffusaDumort., an introduced species.

ISSN:0008-4026    

DOI:10.1139/b85-026

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

A multivariate extension of univariate sample size estimation is outlined that enables one to determine sample size for a multivariate study. The procedure is presented and illustrated by application to intraindividual and interindividual variation of cone morphology in a population ofPicea sitchensis(Bong.) Carr. The method involves the stabilization of a scalar estimate of the structure of the correlation matrix (the determinant) among variables for a given sample size. The sample-specific dependency of previously described methods is avoided by random selection of several replicates in nonstructured and structured (nested) models. The procedure is best applied in pilot studies where it can aid in the characterization of multivariate data prior to analysis. Additionally, repeatability estimates for cone scale morphology are presented.

ISSN:0008-4026    

DOI:10.1139/b85-027

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

The development of the fruit ofPrunus virginianaL. is followed from full bloom to ripening. The maturation process, which lasts 10 weeks is characterized by three distinct stages. Two periods of rapid growth (at the beginning and the end of ripening) are separated by a stage of retarded growth. Soon after the fertilization, the mesocarp increases in thickness, owing to an enlargement of the cells of the later tissue rather than by an increase in the number of cells. By the end of the first period of growth, the endocarp begins to enlarge. In this situation, the increase of thickness is predominantly due to cell division. At the completion of its development, we observed two distinct zones in the endocarp. The inner portion is formed of 6 to 7 layers of lignified cells extending tangentially along the cavity, while the outer portion is composed of 15 to 20 isodiametric sclereids. The second stage of the development is characterized by an important delay in the growth of the pericarp. However, the cessation of the increase coincides with some important changes in the seed, while the endosperm, and almost simultaneously, the embryo rapidly expand. During the maturation of the seed, we noted that the endosperm cells enlarged, their cytoplasm became thicker, and their arrangement in the tissue appeared more regular. Throughout the third phase of the development, a new period of rapid growth is observed. In the mesocarp, the cells enlarged in the radial direction. The development of the fruit ofP.virginianaL. and its vascular patterns have been analysed in comparison with those of other fruits ofPrunus.

ISSN:0008-4026    

DOI:10.1139/b85-028

出版商:NRC Research Press    

年代:1985

数据来源: NRC