摘要:

Patterns of flowering and pollination visit ofCarpobrotusspp. were examined to determine the hybridization potential between the introduced succulent perennialCarpobrotus edulisand its native congener,Carpobrotus chilensis, in coastal California. Both species flower from March to July and both are visited by the same Thysanoptera and Coleoptera taxa. Flowers from hybrid-appearing individuals were intermediate in corolla diameter. Emasculation and bagging experiments suggest thatC. edulisand hybrid morphotypes have facultative agamospermia, whereasC. chilensishas facultative self-fertilization. EmasculatedC. chilensisdid not set seeds. Pesticide application and flower bagging suggest that 80% of seed set in self-pollinatedC. chilensisflowers is mediated by thrips. Our results suggest that there is high potential for natural hybridization inCarpobrotusspecies in California and thatCarpobrotuspopulations can persist without cross-pollination.Key words:Carpobrotus, exotic species, facultative agamospermia, hybrid fitness, invasion, pollination preference.

ISSN:0008-4026    

DOI:10.1139/b98-130

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

A group of 49Amanitaspecies that had been thoroughly examined morphologically and anatomically was analyzed by DNA sequence comparison to estimate natural groups and phylogenetic relationships within the genus. Nuclear DNA sequences coding for a part of the ribosomal large subunit were determined and evaluated using neighbor-joining with bootstrap analysis, parsimony analysis, conditional clustering, and maximum likelihood methods. SectionsAmanita,Caesarea,Vaginatae,Validae,Phalloideae, andAmidellawere substantially confirmed as monophyletic groups, while the monophyly of sectionLepidellaremained unclear. Branching topologies between and within sections could also partially be derived. SubgeneraAmanitaandLepidellawere not supported. TheMappaegroup was included in sectionValidae. Grouping hypotheses obtained by DNA analyses are discussed in relation to the distribution of morphological and anatomical characters in the studied species.Key words: fungi, basidiomycetes phylogeny, Agaricales,Amanitasystematics, large subunit rDNA, 28S.

ISSN:0008-4026    

DOI:10.1139/b98-129

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Dimensions of anatomical and morphological attributes of leaves can influence physiological response to changes in environment over time. Linking structural attributes of leaves to crown position and tree size within naturally developing cohorts of trees can provide a clearer understanding of changes in crown morphology for a species. This study examined leaf anatomy and morphology ofBetula papyriferaMarsh. growing in two stages of stand development of interior cedar-hemlock forest, northern British Columbia. Anatomical and morphological measurements of leaves located at six different positions within the crown were made on trees selected from stands that originated 15 years (small tree size) and 145 years (large tree size) after catastrophic fire. Leaf area and mass were measured in the field. Microscopic measures were made in the laboratory of thicknesses of leaves, cuticle, upper and lower epidermis, palisade, and spongy mesophyll. Stomatal density and stomatal aperture lengths were also determined. Leaf anatomy and morphology varied significantly with position in the crown and among size-classes of trees. Changes in leaf anatomy observed among positions within the crown reflect the changing availability of light and moisture experienced during crown development. For both size-classes of tree the largest anatomical dimensions of leaves were at the outer and uppermost parts of the crown, whilst the smallest were at the lower and innermost parts. Foliage of large trees (145 years) exhibit leaf attributes characteristic of the sun-shade dichotomy reported in the literature, but this was not shown for foliage of young saplings (15 years). For the small trees (15 years) the largest leaves were located at the top of the crown while the smallest were located at the bottom. This has been reported for many tropical pioneers but is in contrast to the usual sun-shade dichotomy of temperate pioneers. The large trees (145 years) followed the typical pattern with the smallest leaves at the top of the crown. Information from this study contributes to our understanding of foliar development of tree crowns by demonstrating how leaf structure changes with crown position and tree size under stand competition.Key words:Betula papyrifera, British Columbia, crown development, cuticle thickness, leaf area, palisade mesophyll, paper birch, stand dynamics.

ISSN:0008-4026    

DOI:10.1139/b98-128

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Seed banks of two seashore meadows were studied on the west coast of Finland (latitude 61°30'-61°33'N, longitude 21°28'-21°41'E). Samples were taken in June to a depth of 10 cm in the geolittoral zone of the grazed and ungrazed transects. The grazed samples were halved lengthwise: one half was grown immediately, the other after cold treatment. One third of the all samples was treated as controls, one third was watered with brackish water, and one third was given a pesticide treatment. Altogether, 13 926 seedlings germinated and 25 species were identified (three annuals, two biennials, and the rest perennials). Most seedlings were perennial monocots, withJuncus gerardiiLoisel. the most abundant species. The seed bank was significantly larger and richer in the ungrazed site than in the grazed site. Cold treatment reduced the number of germinating species and seedlings. In the grazed and non-cold-treated samples, the numbers of species and seedlings were highest in the pesticide treatment. In ungrazed samples there were no significant differences among treatments. After the cold treatment, the least number of species and seedlings was produced by the salt-water treatment. Changing brackish water to tap water led to a burst of germination, especially ofJ. gerardii. The seed bank of the upper geolittoral zone was richer than that of the middle geolittoral. The multivariate classification and ordination groupings are based on the abundances ofJ. gerardiiandGlaux maritimaL.; different treatments were not distinguishable. There was a low resemblance between the seed bank and the aboveground vegetation.Key words: seed bank, salinity, pesticide, seashore meadow, cold treatment, vegetat

ISSN:0008-4026    

DOI:10.1139/b98-102

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

The occurrence of deuteromycetous entomopathogenic fungi was examined in 266 soil samples representing 86 locations across temperate and near northern habitats in Ontario, Canada. Entomopathogenic fungi were isolated by baiting the soil with waxworm larvae,Galleria mellonellaL., and incubating at 8, 15, or 25°C. Entomopathogenic fungi were isolated from 91% of the locations sampled across Ontario. The most abundant species wereMetarhizium anisopliae(Metschn.) Sorok. (357 isolates) andBeauveria bassiana(Bals.) Vuill. (187 isolates). Thirteen isolates ofPaecilomycesspp. were also found.Beauveria bassianawas isolated more frequently in soils from near northern locations, relative toM. anisopliae.Beauveria bassianawas isolated more frequently from larvae baited in soils incubated at 8 and 15°C, whileM. anisopliaewas isolated most frequently at 25°C. Thus,B. bassianais more psychrophilic thanM. anisopliae. From 47 of the locations in a temperate area (southern Ontario and the Kawartha Lakes region), two sites, one from an agricultural habitat and one from a natural habitat, were sampled within 1 km of each other. In these locations,B. bassianawas predominantly recovered more often from soils of natural habitats, whileM. anisopliaewas recovered more often in agricultural habitats. The occurrence ofM. anisopliaeandB. bassianawas not related to soil type or pH.Key words:Metarhizium,Beauveria, entomopathogenic fungi, fungal population biology, soil ecolo

ISSN:0008-4026    

DOI:10.1139/b98-115

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Melanized, root-colonizing fungi are ubiquitous. Their ecological role, however, is poorly understood, and results of studies of associations between these fungi and their potential host plants are controversial. The culture system under which the association is studied may also affect the host-fungus interaction. Two experiments on the association betweenPinus contortaDougl. ex Loud., and a root-inhabiting endophytic fungus,Phialocephala fortiniiWang & Wilcox, were conducted to study the host response to inoculation. First,Pinus contortaseedlings were inoculated with two strains ofPhialocephala fortiniiand grown under aseptic conditions with five levels of glucose in the medium. Multiple linear regression analysis was employed to study the effects of inoculation and glucose concentration. Second, the same two strains ofPhialocephala fortiniiwere inoculated onPinus contortaseedlings in open pot cultures. Inoculation resulted in substantial increase in all biomass components of the host plant in the aseptic culture system. Total biomass, for example, was increased approximately 60 and 90% when seedlings were inoculated with strain 1 and strain 2, respectively. No seedling mortality was observed following fungal inoculation after 6 months of incubation. Inoculation increased host biomass with increasing glucose concentration, while glucose concentration did not significantly affect host biomass when no inoculum was added. Inoculation lowered foliar nitrogen and phosphorus concentrations. The effect of glucose concentration on the foliar nutrient concentrations varied between the two strains. In the open pot cultures, inoculation did not affect biomass or foliar nutrient concentration. We hypothesise that the observed increases in host growth in the aseptic culture system are due to fungal respiration in a closed culture system, the carbohydrates made available to the host plant by the fungus, or, most likely, to a combination of both factors. The ecological role ofPhialocephala fortiniiand the validity of aseptic culture assays are discussed.Key words: dark-septate endophytes, deuteromycetes, fungi, host-fungus associations, root endophytes, symbiosis.

ISSN:0008-4026    

DOI:10.1139/b98-098

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

The developmental basis of floral polymorphism was investigated in the tristylous invasive species,Lythrum salicariaL. (Lythraceae). In tristylous species, the stigmas are positioned above (in the long morph), below (in the short morph), or between (in the mid morph) the outer and inner staminal whorls. Flower samples were collected at three different growth stages (early, pre-anthesis, and post-anthesis) from three genotypes from each of the three morphs to observe morph-specific differences in growth patterns of filaments and styles and their constituent epidermal cells. From each flower, I measured the length of styles and two types of stamens and their epidermal cells at the basal, intermediate, and apical regions of each organ. Differentiation of organ levels begins at a very early stage. Growth rate of the long pistil is higher than in the mid pistil followed by the short pistil. However, the growth rate of epidermal cells is higher in the short style followed by the mid and long styles. The number of cells does not increase during style development in the short morph but does increase in the long and mid morphs. Although the relative growth of the outer stamens is greater than in the inner stamens in all three morphs, the relative cell size is greater in the inner stamens than in the outer stamens. Cell size differs between outer and inner stamens in the long and mid morphs but not in the short morph. The intermediate cells are larger compared with the basal and apical cells of the stamens and styles. The number of epidermal cells increases in the outer stamens during development, whereas it remains constant in the inner stamens of the mid morph and increases only slightly in the inner stamens of long morph.Key words: floral development, growth and division of epidermal cells, heterostyly, purple loosestrife, style and stamen growth, style-stamen polymorphism.

ISSN:0008-4026    

DOI:10.1139/b98-099

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Localization of the source of the signal(s) controlling correlative inhibition of leafy spurge root buds (underground adventitious shoot buds located on the lateral roots) was studied by sequential removal of various plant organs. It was determined that full correlative inhibition of root buds was lost only after excision of all aerial tissue from the plant, or after excision of all aerial tissue except the stem. If mature leaves or growing axillary buds (or both) were left intact, no growth of root buds was observed. The synthetic auxin, alpha-NAA, prevented release of apical dominance and subsequent outgrowth of stem and crown buds when applied to the cut end of the stem or crown. Exogenous application of NAA to either the stem or the crown had little effect on root bud growth. Application of the auxin transport inhibitor NPA around the base of the crown had no effect on root bud quiescence. These data are not consistent with the previous studies (Weed Sci. 35: 155-159 (1987)) that indicate a role for auxin in maintenance of correlative inhibition of root bud growth in leafy spurge. The results of auxin transport inhibitor studies presented here suggest that correlative inhibition of root bud growth does not rely on the classic polar auxin transport system.Nomenclature: leafy spurge,Euphorbia esulaL.#3EPHES; NAA, naphthalene acetic acid; NPA,N-1-naphthylphthalamic acid; TIBA, 2,3,5-triiodobenzoic acid.Key words: root buds, apical dominance, auxin, NPA.

ISSN:0008-4026    

DOI:10.1139/b98-138

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

The objective of this study was to describe the different morphological gradients being used as the basis for the development of the shape of the stem system in young forest-grown 7-year-old beeches, while characterizing the structural evolution of successively produced annual shoots in relation to the timing of their formation as well as their topological situation among tree stem systems. Three simple morphogenetic gradients explain the developmental dynamics of their overall stem system and the evolution in time and space of the morphogenetic functioning of their primary meristem structure. The first one illustrates structure settings by progressive increase of annual growth rate (increase of foliated node number and of annual shoot length) and of the branching angle of the trunk, as well as of successively produced twigs. The second gradient is represented by the "primary acrotonic" phenomenon described by Rauh in beech, which encourages formation and development of the highest lateral axes on the annual shoot. The third one is characterized by a gradual reduction in annual growth rate as well as of the branching angle of the lowest axes of the tree, indicating their decline and their imminent elimination by natural pruning.Key words: beech, architecture, growth, ramification, polycyclism, morphology.[Translated by editorial staff]

ISSN:0008-4026    

DOI:10.1139/b98-053

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Studies of soral development in the tree-fern family Dicksoniaceae in comparison with the Cyatheaceae led to (1) recognition of two basic patterns in the Dicksoniaceae, (2) clarification of marginal versus superficial sori and their indusia in tree ferns, and (3) phylogenetic interpretations. InCibotiumthe sorus originates directly from the marginal initial file. The outer and inner indusia arise simultaneously, early in development, on the adaxial and abaxial sides of the receptacle, respectively. The receptacle inDicksoniaoriginates from a shifted segment of the marginal initial file. The outer indusium is initiated first, approximately at the same time as the receptacle. The initial cells of the marginal meristem give rise to the soral receptacle in both groups of dicksoniaceous genera. Preliminary studies of soral morphogenesis in some cyatheaceous genera indicate that abaxial derivatives originate the sorus. The Cyatheaceae have a single, abaxial indusium proximal to the sorus at maturity, or none. Consideration of these morphogenetic data in light of recent molecular phylogenies suggests that fundamental changes in the meristematic origin of tree-fern sori have taken place since the origin of the lineage that includes both Dicksoniaceae and Cyatheaceae.Key words:Cibotium,Dicksonia, Dicksoniaceae, sorus, tree ferns.

ISSN:0008-4026    

DOI:10.1139/b98-122

出版商:NRC Research Press    

年代:1998

数据来源: NRC