摘要:

Several species of the genusTeucriumsectionpoliumfrom the mediterranean region are difficult to identify because of their wide morphological variability. The relationship between the morphological variations and the distribution of caffeic acid esters was studied. The results show that the taxonomic value of these markers is different depending on the nature of the molecule. Ecological factors interfere with the presence of verbascoside (diglycoside) more than they do with those of stachyoside and T2(triglycosides). The presence of these latter molecules confirms the close relationship betweenT.poliumsubsp.poliumandT.capitatum. The stachyoside present inT.poliumsubsp.poliumalso allows the distinction, in overlapping areas, of intermediary forms toT.aureumsubsp.aureum, in which it is absent. Poliumoside is a specific marker for thepoliumsection. It is never found in the other sections, where it is replaced by teucrioside and chlorogenic acid.

ISSN:0008-4026    

DOI:10.1139/b88-145

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

In the Whapmagoostui area (east of Hudson Bay), tree harvesting by Crée Indians in lichen woodlands affects the form and the growth of surviving trees and also the forest population dynamics. A study of the growth form of white spruce (Picea glauca(Moench) Voss.) and black spruce (Picea mariana(Mill.) B.S.P.) that have been pruned shows the efficiency of a total traumatic reiteration process. After several years, the annual radial growth was equivalent to that recorded before pruning. In clear-cutting areas (more than 75% of trees removed), the increase in the radial growth of spared trees was 400 to 700%. The main factors that govern the success of regeneration in cutting areas are the rather small extension of the openings (<0.005 km2), the low intensity of tree harvesting (<75% of trees over 90% of the surface), the physical conditions of the lichenous ground cover and the abundance of the lignified debris after clearing vegetation, and the climatic conditions in the subsequent years.

ISSN:0008-4026    

DOI:10.1139/b88-146

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Anthocyanin production in roots and shoots ofZea maysL. seedlings was higher in blue than in red light and was very low in far red light. Under dichromatic irradiation, a phytochrome mediation of a blue-dependent photoreaction was evident. Pretreatments with both white and blue light allowed increased anthocyanin production under subsequent inductive conditions, as did occurs in treatments with continuous blue, red, far red, or white light. It is suggested that the effect of light pretreatments on phytochrome-controlled anthocyanin formation may differ from that controlled by the combination of cryptochrome and phytochrome.

ISSN:0008-4026    

DOI:10.1139/b88-147

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Systemic resistance to anthracnose caused byColletotricum lagenariumwas induced in cucumber by inoculation with fungal conidia. Control and immunized leaves were examined by both light and electron microscopy before and after subsequent challenge with the fungus. Penetration through the epidermal wall was evident 36 h after challenge and was followed by hyphal proliferation and host-cell destruction in control tissues. Penetration was rarely seen in immunized tissues before 72 h, but at 24 h, invaginations of the appressorial wall were observed, as well as highly electron opaque epidermal walls beneath the appressoria. At 72 h, thin penetration pegs were seen within the dense host wall, and at 96 h, the peg was embedded within the underlying papilla and aggregates of callose-like material. Penetration through the epidermis was rare in immunized tissue, but when it was observed, development appeared to be similar to that in control leaves. Evidence is presented to show that ultra-structural changes in immunized tissues as well as in the fungus occur within 24 h after challenge of the host. There appears to be a correlation between the comparatively few lesions observed macroscopically in immunized leaves and the sparsity of successful penetrations into host mesophyll cells.

ISSN:0008-4026    

DOI:10.1139/b88-148

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

The main stem development and the photosynthetic activity of leaves 2 to 9 were studied in soja (Glycine max(L.) Merr.) at the leaf blade extension and adult stages. A correlation between the different leaf growth parameters (rates, durations) and the phyllochrone has been demonstrated. That correlation varied with the age and rank of the leaf. Moreover, the existence of correlations between net photosynthesis on one hand and the rate of development and the leaf growth kinetics on the other hand reveals an interdependence between photosynthesis and morphogenesis. [Journal translation]

ISSN:0008-4026    

DOI:10.1139/b88-149

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Silica bodies were observed in populations belonging to four tetraploid taxa of the genusDactylis. Twelve characters were used to describe those elements, which allow some comparisons to be made between populations growing wild and those growing in experimental plots. They also show the taxonomic importance of the silica bodies. This new approach leads to both a confirmation and a better understanding of the morphological affinities previously observed among the different taxa.

ISSN:0008-4026    

DOI:10.1139/b88-150

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

The fine structure of zoospores of twoZygorhizidiumspecies pathogenic on the freshwater planktonic diatomAsterionella formosaHassall, are described.Zygorhizidium affluensCanter andZ.planktonicumCanter have monocentric operculate sporangia and zoospores which have single lipid globules to which the cell nucleus and single mitochondrion are closely adpressed. Several features placeZ.affluensin the ChytridialessensuBarr. These include having its kinetosome and nonfunctional centrioles not closely associated with the nucleus and having a ribosome-rich core region delimited by endoplasmic reticulum. However, there are no cytoplasmic microtubules or membranous rumposome complex in this species. In contrast, zoospores ofZ.planktonicumhave dispersed or loosely aggregated ribosomes and a rumposome complex. The zoospores of this species appear to belong to the same morphological subtype as the pathogenic genusSynchytrium, which has also been placed in the Chytridiales.Zygorhizidium planktonicumzoospores possess a number of vesicle types apparently unique to this species and have a nonfunctional centriole which is constructed of a ring of singlet microtubules and is often completely disassociated from the kinetosome. Both species contain "peripheral vesicle" systems which are probably involved in regulating internal water potential. From this study it seems unlikely that the two species are closely related, although they have been placed in the same genus.

ISSN:0008-4026    

DOI:10.1139/b88-151

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Among temperate-zone plant species, fruits with fat-rich pulp have been predicted to disappear more rapidly than low-fat fruits, in part because of more rapid decay by microbes. The influence of fat content of pulp on the susceptibility of fruits to microbial invasion and the rate of pulp deterioration after invasion were examined usingCornus amomumfruits (approximately 5.8% crude fat) andC.racemosafruits (approximately 23.1% crude fat). Fruits were surface sterilized, punctured with a sterile needle or left undamaged, and inoculated with sterile water, a suspension of bacteria, or a suspension of fungal spores. The two species did not differ significantly in the number of days to first deterioration (= susceptibility), but wholeC amomumfruits deteriorated faster than did wholeC.racemosafruits after invasion was first visible. This difference between species persisted when the difference in mean dry pulp mass was taken into account using an exponential model of pulp decay. The twoCornusspecies did not differ in rate of pulp deterioration (milligrams dry tissue per day) when a linear model of microbial decay of pulp was used. In these two species, higher fat content of pulp does not yield greater susceptibility to invasion or higher rate of deterioration by microbes.

ISSN:0008-4026    

DOI:10.1139/b88-152

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Hydraulic conductance of tracheids was studied in either petioles or young stems of six species of seed plants having various types of intertracheid pitting. Measured conductances were compared with estimates based on Hagen–Poiseuille flow through ideal capillaries and with predictions from a biophysical model incorporating observed anatomical characteristics of tracheids and intertracheid pits. Conductance of the xylem, expressed as a percentage of the ideal capillary flow prediction, varied from an average of 88% for a species containing only very narrow tracheids to less than 35% for species with large-diameter tracheids. The biophysical model allowed fairly close predictions of conductance for all species except one, where an estimate of the pit membrane resistance could not be experimentally obtained. For individual tracheids, conductance was largely a function of lumen diameter, pit membrane resistivity, and the exposed area of the pit membranes, as determined by pit shape, size, and frequency. For wide tracheids, scalariform-pitted elements showed a linear increase in conductance with an increase in lumen diameter; however, for tracheids with large circular pits, the conductance increase afforded by a wider lumen declines as lumen diameter increases. These model simulations demonstrate the increasing significance of intertracheid pitting in obstructing flow as lumen diameter increases.

ISSN:0008-4026    

DOI:10.1139/b88-153

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Vegetation composition of the shrub–tree and herb layers was sampled in 70 successional aspen (Populus tremuloidesandPopulus grandidentata) stands of different ages (1–90 years) on a variety of sites in northern lower Michigan. Physical and chemical characteristics of soil profiles were also measured at each site. Three stand groupings were identified based on site conditions and detrended correspondence analysis (DCA) ordination of the vegetation. Sandy dry-mesic soils support forests ofAcer rubrum,Quercus rubra,Pinus resinosa, andPinus strobus. On lowland sandy soils with a fluctuating water table,Pinus strobus,Abies balsamea,Viburnum lentago, andViburnum cassinoidesare important. Mesic soils with stratified calcareous layers or clay till substrates supportAcer saccharum,Fagus grandifolia,Tilia americana,Fraxinus americana,Ostrya virginiana, andAcer pensylvanicum. Canonical correlation analysis (CCA) was used to compare DCA scores with soil variables; first-axis DCA scores were correlated with a suite of soil variables and stand age was correlated with second or third DCA axis scores. Separate DCA ordinations of the dry-mesic and mesic groups revealed successional relations on these sites. On dry-mesic sites,Pinus resinosaandPinus strobusincrease in importance with stand age, whilePrunus serotina,Prunus virginiana,Prunus pensylvanica, and the aspens decrease. On mesic sites, early successional species include the aspens,Corylus cornuta,Prunus serotina, andPrunus pensylvanica.Fagus grandifolia,Acer pensylvanicum,Quercus rubra,Viburnum acerifolium,Betula papyrifera,Acer rubrum, andTilia americanaare more abundant in mature mesic-site stands. Ordinations of the herb data were remarkably similar to those for trees and shrubs except on dry-mesic sites. Much of the residual variability in vegetation not accounted for by site conditions and stand age is probably related to historical factors such as the nature of disturbance and variations in seed rain.

ISSN:0008-4026    

DOI:10.1139/b88-154

出版商:NRC Research Press    

年代:1988

数据来源: NRC