摘要:

The vesicular–arbuscular mycorrhizal (VAM) fungusGlomus aggregatumand the legume speciesAcacia mangiumwere grown together in a manganese-rich oxisol at pH 4.3 to 6.0 and at soil P concentrations favorable for VAM-host growth (0.02 mg ∙ L−1) and sufficient for non-VAM host growth (0.8 mg ∙ L−1). At the lower P concentration, vesicular–arbuscular mycorrhizal fungal (VAMF) colonization of roots increased as soil pH increased from 4.3 to 5.0. However, colonization of roots was not significantly influenced by further increases in pH. Growth ofA.mangiumat 0.02 mg P/L in the presence ofG.aggregatumwas inferior to that observed at 0.8 mg P/L, suggesting that there was some degree of host–endophyte incompatibility. Increasing P concentration from 0.02 to 0.8 mg P/L increased target soil pH in the unlimed soil from 4.3 to 4.8 and reduced the concentration of available soil Mn from 13.2 to 2.1 mg ∙ L−1. Thus, the better plant growth observed at the higher P concentration at pH < 5 was mainly due to the alleviation of Mn toxicity due to the precipitation of the cation directly by excess phosphate and (or) phosphate-induced elevation of soil pH. The poor VAMF inoculation effect observed at the lower soil P level in the unlimed soil was thus largely due to the toxicity of high concentrations of Mn2+and H+ions.Keywords: hydrogen ion, calcium, manganese-rich, manganese toxicity, pinnule P, soil acidity, VAMF colonization, VAMF effectiv

ISSN:0008-4026    

DOI:10.1139/b96-021

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

TheAster novi-belgiiL. complex is one of the least understood groups of this genus in Quebec. The goal of this study is to better circumscribe the taxa often confused with it (A.puniceusandA.anticostensis), to determine whether species described within the complex are valid (A. "foliaceus",A.johannensis, etc.), and to establish their habitat and distribution. Samples were collected throughout the range of the species in Quebec.Aster novi-belgiivar.novi-belgiiandA.novi-belgiivar.crenifoliusindividuals are 2n = 6x = 48; a count of 2n = 80 is reported forA. "longifolius''.Amorphometric analysis using principal components and discriminant analyses shows thatA.novi-belgiiis easily distinguished fromA.puniceusandA.anticostensis. No segregate species can be recognized within theA.novi-belgiicomplex. However, at the infraspecific level, two varieties seem recognizable: a coastal, robust morphotype in the Gaspé Peninsula (A.novi-belgiivar.crenifolius), and a strongly pubescent form (A.novi-belgiivar.villicaulis) on the Saint-Jean and Restigouche rivers. The new combinationA. novi-belgiiL. var.crenifolius(Fern.) Labrecque & Brouillet is proposed.Keywords: Asteraceae,Aster, biosystematics, Quebec, morphometry.

ISSN:0008-4026    

DOI:10.1139/b96-022

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

We tested the utility of fluorescent dye particles as pollen analogs for hummingbird-pollinatedSilene virginica(Caryophyllaceae) by comparing the movement of pollen and fluorescent dye across sequentially visited emasculated flowers. We found no differences in either the intercept or the slope of the regressions of the two particle types on floral visitation sequence. In addition, the presence of fluorescent powder on the stigmas of a flower was a good indicator of pollen transferred to that flower. Both pollen and dye particles were transported almost identical distances in the flower sequence. These data indicate that fluorescent powder is a good pollen analog forS.virginica. We compare our findings with previous studies examining the utility of fluorescent dye as a pollen analog.Keywords: pollen analog, fluorescent dye, pollen carry-over.

ISSN:0008-4026    

DOI:10.1139/b96-023

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

From May to October, relationships of total numbers of airborne fungal propagules between indoor and outdoor sampling sites were very strong, particularly forAlternariaandLeptosphaeria, while that for unidentified ascospores was positive but to a lesser degree. Indoor and outdoor counts ofCladosporium,Epicoccum,Ganoderma, unidentified spores, hyphal fragments, and biodiversity (total number of fungal genera) were also significantly positively related. There appeared to be no functional relationship betweenAspergillus/Penicilliumconidia in indoor and outdoor air. From November to April, indoor and outdoor counts ofAlternaria,Ganoderma, and hyphal fragments displayed negative relationships, but there was a positive correlation forCladosporium,Epicoccum,Leptosphaeria, unidentified ascospores, total fungal spores, unidentified spores, and biodiversity. Once again, no functional relationship was detected betweenAspergillus/Penicilliumindoors and outdoors. The functional relationships of airborne fungi with indoor environmental factors are examined and discussed. A lack of causal relationships, as detected by path analysis, indicates that airborne spores ofAlternaria,Leptosphaeria, unidentified ascospores,Coprinus, andGanodermacame mainly from outdoor sources. All path models fitted this hypothesis well, except forAspergillus/Penicillium. On the other hand, path analysis suggested that there were probably indoor sources ofCladosporium,Epicoccum,Aspergillus/Penicillium, unidentified basidiospores, and unidentified spores. Most of the models explained a large proportion of variance of indoor airborne fungi.Keywords: airborne fungal spores, redundancy analysis, path analysis.

ISSN:0008-4026    

DOI:10.1139/b96-024

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

Comparative studies of the reproductive biology and pollination ecology of closely related species allow us to test several ideas related to the evolution of selfing taxa from outcrossing ancestors. The existence of closely related species in the same habitat provides a particularly useful opportunity to examine this issue. A variety of floral traits likely to be associated with the reproductive system of three sympatricVacciniumspecies (V.myrtillus,V.vitis-idaea, andV.uliginosum)were quantified in a heathland in the Upper Ardennes, Belgium. These traits included the length and width of the corolla, the number and size of the anthers, the number of pollen tetrads and ovules, and the length of the style. Pollen to ovule ratios suggest a mixed mating system in the three species. The greater pollen to ovule ratio and stigma–anther separation inV.vitis-idaeasuggest that it functions more as an outcrosser than the two congeners. The effects of caging, emasculation, and artificial pollination on fruit and seed set differed among years and among the three species. Supplementary pollination increased fruit set and fruit characteristics (particularly seed number) relative to natural pollination in the three species. The three species showed a varied but poor capacity to self in the absence of pollinators. Seed set per fruit was lower in the spontaneously selfed flowers in comparison with hand-crossed pollinated flowers inV.myrtillusandV.vitis-idaeabut not inV.uliginosum. This higher ability to self inV.uliginosumindicates a lower capacity to self in the absence of pollinators. However, all the three species were at least partially self-compatible. Together the floral traits and selfing ability suggest that the polyploidV.uliginosumappears to be more highly selfing than the two diploids, particularlyV.vitis-idaea.Keywords: floral biology, mixed mating, mating system,Vaccinium, seed set.

ISSN:0008-4026    

DOI:10.1139/b96-025

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

Allozyme variation in 11 Minnesota populations ofLemna minorL. was studied, using 11 enzyme systems, resolving 16 putative loci from 285 plants. Significant deviations from Hardy–Weinberg frequencies occurred in several populations that had excesses of heterozygotes at several loci. While genotypic diversity and evenness measures are similar to other vegetatively reproducing plants (D = 0.541,E = 0.607), very few multilocus genotypes per population were found (mean = 4.0). Substantial population structure was evident (FST = 0.407), apparently reflecting low levels of gene flow (Nm = 0.30) despite the capacity of this species for dispersal of plantlets. This low level of gene flow and apparent low frequency of sexual reproduction has produced substantial levels of genetic divergence among populations, despite an absence of morphological differentiation.Keywords: allozymes, genetic structure, hydrophily,Lemna, vegetative dispersal, vegetative reproduction.

ISSN:0008-4026    

DOI:10.1139/b96-026

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

Ungerminated conidia ofBlumeria graminisf.sp.hordeiwere prepared for transmission electron microscopy using cryofixation and freeze-substitution. Conidia were uninucleate, with the nucleus located in the central portion of the conidium, typically off to one side. The nucleus was spherical and contained a distinct nucleolus with an associated satellite. Conidia contained numerous large, spherical vacuoles that occupied much of the spore volume. Vacuolar contents were mostly homogeneous with occasional electron-opaque inclusions. Much of the cytoplasm consisted of lightly staining aggregations of glycoprotein that could be labelled with Concanavalin A – gold and that stained darkly using a modified Thiéry's reaction specific for carbohydrates containing vicinal hydroxyl groups. Mitochondria, strands of endoplasmic reticulum, Golgi body equivalents, multivesicular bodies, microbodies, Woronin bodies, and microtubules were present in the conidium. Cuboidal, stacked, electron-translucent structures also were present in the cytoplasm. The conidium was surrounded by a two-layered wall that labelled with gold-conjugated wheat germ agglutinin-ovomucoid, indicating the presence of chitin. The wall between attached conidia contained areas that did not label with gold-conjugated wheat germ agglutinin-ovomucoid.Keywords:Erysiphe, ultrastructure, electron microscopy, freeze substitution.

ISSN:0008-4026    

DOI:10.1139/b96-027

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

Eleocharis obtusaandEleocharis ovataare recognized as distinct species or combined in recent taxonomic literature. To assess their morphological relationship and to evaluate all morphological characters potentially useful for their separation, 11 floral and achene characters were measured on 130 eastern Canadian herbarium specimens. Tubercle width was bimodally distributed and completely separated groups established on the basis of stamen number: plants referable toE.ovatahad tubercles less than 0.5 mm wide and two stamens, whereas plants referable toE.obtusahad tubercles greater than 0.5 mm wide and three stamens. Since determination of stamen number requires dissection under a microscope and tubercle width requires accurate measurement, the most readily utilized character was found to be the ratio of tubercle width to achene width, which can be measured or estimated. The tubercle was less than 2/3 the width of the achene inE.ovataand more than 2/3 inE.obtusa. Differences in these characters were associated with significant but less dramatic differences in other characters, suggesting that the two taxa should be treated as distinct species.Keywords:Eleocharis obtusa,Eleocharis ovata, Cyperaceae, taxonomy, classification, Canada.

ISSN:0008-4026    

DOI:10.1139/b96-028

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

The broad-leaf paper bark or melaleuca tree (Melaleuca quinquenervia(Cav.) Blake) is an emergent, semiaquatic tree whose morphological plasticity allows it to invade wetland and terrestrial habitats. While studying the effect of hydroperiod on melaleuca seedlings, two types of aquatic leaf forms were observed under submersed conditions. Linear leaves developed at least 9.5 cm below the water surface and were associated with short internodes. Short, broad, incurved transitional leaves formed as the seedlings approached the water surface. Aerial leaves were flat and spatulate to oblanceolate. Leaf length to width ratios, stomatal density, and shoot internode lengths were significantly different between the three leaf forms. Characteristics of submersed melaleuca seedlings are similar to those of other aquatic heterophyllic plants that grow in areas where water levels fluctuate. An increased understanding of morphological variations of this invasive tree may lead to additional control methods and mechanisms.Keywords:Melaleuca, aquatic, heterophylly.

ISSN:0008-4026    

DOI:10.1139/b96-029

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

The relationships between estimates of mycorrhizal activity, time following reclamation, and soil edaphic factors were investigated over a period of 2.5 years during reclamation of five abandoned surface mine sites in western Kentucky. These sites were reclaimed at different times and were in varying stages of revegetation. At the seeding stage of reclamation and soon thereafter, propagule and spore population densities were low but invariably present. Roots recovered from minespoil during this period were not colonized, and colonization was not observed until a full year following reclamation. During the first 2 years following reclamation, colonization of roots, population densities of propagules and spores, and total spore volume increased rapidly. Thereafter, vegetative and mycorrhizal parameters appeared to stabilize. Each estimate of mycorrhizal activity in minespoil was highly correlated with time following reclamation and all other mycorrhizal parameters. Edaphic factors with positive relationships to mycorrhizal propagule and spore population densities included soil organic matter and calcium.Keywords: Glomales mycorrhizal fungi, reclamation, abandoned minespoil, most probable number, propagule population density.

ISSN:0008-4026    

DOI:10.1139/b96-030

出版商:NRC Research Press    

年代:1996

数据来源: NRC