摘要:

The standing biomass accumulation of lichens from the generaAlectoria,Bryoria, andUsneawas studied along two environmental gradients, altitude and height along the vertical tree axis, in an old-growth balsam fir (Abies balsamea(L.) Mill.) forest. Lichens were sampled from 50 trees in five sampling sites at an altitude of 720-1068 m asl and encompassing three vegetation belts (mountain, subalpine, and alpine). The lichen biomass accumulation rate was studied at branch and tree levels. The Gompertz equation was used to assess the relationship between time since lichen colonization and standing lichen biomass. The relationship between tree lichen biomass and age was not significant. Colonization delay was assumed to correspond to the age of the youngest branch supporting a given lichen taxon, and our results show that it increased from mountain to alpine belts. Variations in lichen accumulation were related to the branch position along the tree height and altitude. Lichen biomass accumulation rates decreased from tree top to base. We speculate that this reduction reflects a response to microclimatic gradients, aging of thalli, fragmentation, competition, succession, and caribou grazing. The accumulation rate was greater in the mountain belt (r= 0.063) than in the alpine belt (r= 0.027). In the subalpine belt, the relationship between lichen biomass and time was not significant (p> 0.05). The decrease in accumulation rate along the altitudinal gradient may be primarily explained by climatic conditions.Key words: arboreal lichens, lichen biomass accumulation, altitude effect, height in tree effect,Alectoria,Bryoria,Usnea.

ISSN:0008-4026    

DOI:10.1139/b98-144

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

We investigated variation in ovule development within and among fruits in garlic mustard,Alliaria petiolata(M. Bieb.) Cavara & Grande. Individuals were sampled at 14 sites in North America. On average, 94% of ovules showed evidence of fertilization and development. The majority of ovules (mean 68%; range 53.2-82.5%) reached seed maturity. Patterns of seed maturation and abortion varied nonrandomly within and among fruits. In sites in Tennessee, Kentucky, and Ontario, resource limitation seemed to be an important determinant of seed production, as fruits initiated nearest the base of an infructescence were significantly more likely to produce mature seeds than distally located fruits. Also the probability of seed maturation within individual fruits decreased significantly from the pedicellar to the stylar ends. In contrast, for individuals from Ohio sites, the probability of maturing seeds was greatest for centrally located fruits within an infructescence as well as for centrally located ovules within fruits, indicating a greater influence of pollen limitation in addition to resource limitation. We conclude that it could be misleading to infer traits of a species as a whole based on observed patterns of seed maturation in a single site or region. Rather such patterns may reflect prevailing conditions and selection pressures at a local, or regional, scale.Key words:Alliaria petiolata, Brassicaceae, garlic mustard, ovule abortion, seed maturation, patterns.

ISSN:0008-4026    

DOI:10.1139/b98-139

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Salix planifoliaPursh ssp.planifoliais a shrub species presenting some potential for the restoration of disturbed sites in the Canadian Arctic and Subarctic. The performance ofS. planifoliastem cuttings collected in the Kuujjuaq area, northern Quebec, was evaluated in relation to sampling period, plant gender, exogenous auxin and nutrient concentration, rooting duration, watering frequency, and soil volume. Cuttings collected in August, during the active growing season, did not perform as well as those collected in June, October, or February. The only performance variables influenced by plant gender were root number and shoot biomass, for which female cuttings were superior to males. Surprisingly, the application of indole-3-butyric acid inhibited adventitious root and lateral shoot number and biomass, particularly at the highest concentration (10 000 mg·L-1). Increased nutrient availability enhanced root, but not shoot, growth. The best performance was observed when cuttings were grown in a relatively large soil volume (200 mL), watered frequently (twice a day), and allowed a relatively long period to root (70 days).Key words: indole-3-butyric acid (IBA), nutritional status, plant gender, rooting of cuttings,Salix planifolia, sampling period.

ISSN:0008-4026    

DOI:10.1139/b98-177

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Yinmingella mitriformisgen. et sp.nov. (Hyphomycetes), occurring on wood submerged in Tung Chung River on Lantau Island, Hong Kong, is described and illustrated. It is unique in producing short, true chains of holoblastic, aseptate, smooth, black, mitriform conidia from dark brown, flask-shaped conidiogenous cells on hemispherical, black stromata.Yinmingellais compared withHemibeltrania,Hemicorynespora,Mammaria,Janetia,Sporidesmium, andStanjehughesia.Key words: cryo-SEM, dematiaceous Hyphomycetes, freshwater fungi, mitosporic fungi, systematics.

ISSN:0008-4026    

DOI:10.1139/b98-176

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Spadicoides palmicolasp.nov. is described from a senescent leaf ofLicualasp. collected in Brunei. It differs from otherSpadicoidesspecies in having verruculose conidiophores producing verrucose, obclavate, rostrate, multi-euseptate, versicoloured conidia.Spadicoides obclavataKuthub. & Nawawi var.heterocolorataR.F. Castañeda, Guarro & Cano is considered distinct fromSpadicoides obclavata, andSpadicoides heterocoloratacomb.nov. is proposed.Key words: Hyphomycetes,Licuala, palm fungi, systematics, tropical fungi

ISSN:0008-4026    

DOI:10.1139/b98-171

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Les lianes sont des végétaux ligneux grimpants et non autoportants. Mais les lianes sont capables d'autoportance dans les trois situations suivantes : (i) sous conditions de milieu limitantes (lumineuses surtout); (ii) en phase juvénile du développement morphogénétique; (iii) lors des épisodes d'expansion, de renouvellement ou de restauration morphologique. L'autoportance peut concerner tout ou partie du système aérien, l'ensemble des tiges ou quelques tiges seulement. En général, lorsque l'autoportance et la non autoportance affectent plusieurs tiges d'un même système aérien, ces dernières s'opposent aussi par les fonctions biologiques qu'elles exerçent : asexuée et sexuée, sans accrochage et avec accrochage, établissement et exploration. Lorsque l'ensemble du système aérien est autoportant (situations (i) et (ii)), la liane a un mode de vie comparable à celui d'un petit arbre ou d'un arbuste. Une synthèse des données d'architecture anatomique et de stratégie de croissance est présentée. Elle porte sur quelque 40 sites forestiers d'Afrique, d'Amérique et de l'Océan Indien et plus de 400 espèces d'angiospermes tropicales lianescentes. Le polymorphisme des lianes, révélateur des contrastes de vie en milieu tropical, trouve son expression la plus accomplie dans l'opposition des deux modes de vie, autoportant et non autoportant. Sur un plan évolutif, les lianes pourraient représenter une forme ligneuse originale qui aurait conservé ou acquis ces deux modes de vie. Les contraintes de l'environnement et (ou) du développement morphogénétique stimuleraient selon les cas l'organisation autoportante ou non.Mots clés: liane, autoportance, non autoportance, architecture

ISSN:0008-4026    

DOI:10.1139/b98-127

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

The recolonization of the clonal intertidal algaMazzaella cornucopiae(Postels et Ruprecht) Hommersand is considered here, as part of a larger project on its population ecology. Recolonization in Barkley Sound, Pacific Canada, started a few months after completely clearing experimental 100-cm2quadrats in late spring and occurred both by vegetative growth of perennating holdfasts bordering disturbed quadrats and by recruitment from spores. In terms of percent cover, both mechanisms contributed similarly to recolonization during the first 2 years, although vegetative recolonization was highly variable among quadrats. Great spatial variability prevented the detection of a temporal pattern for recruit density on statistical grounds. However, cohort demography showed some degree of seasonality. Turnover rates of recruits were high; they lived 2.6 months on average. Recruitment was highest between fall or winter and midspring (as might be expected, given that reproductive structures appeared in fall and winter) and null in the first two summer seasons. The highest mortality was recorded in summer, when desiccation and irradiance are highest on an annual basis. Frond density was very variable on a spatial scale and did not follow a clear temporal pattern. The average number of fronds per recruit apparently increased between winter and summer, paralleling frond dynamics in mature stands. By monitoring recolonization in quadrats of the same size cleared previously by other researchers, the time of full recovery ofM. cornucopiaewas estimated to be 2.7-3.5 years.Key words: demography, disturbance, Gigartinaceae,Mazzaella cornucopiae, mortality, recolonization, recruitment.

ISSN:0008-4026    

DOI:10.1139/b98-124

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Bitter cherry (Prunus emarginata(Dougl.) Walp.) is a largely unstudied early successional tree native to the Pacific Northwest. We used multiple regression and regression tree analyses to identify the most significant variables describing the distribution of bitter cherry populations in the western Cascade Range of Oregon. To determine if bitter cherry relies on a soil seed bank for regeneration after disturbance, we compared successional patterns to direct measures of buried seed. Measurements from 78 sites ranging in age from 1 to 50 years since disturbance and 29 years of permanent plot data showed density, constancy, and cover were low in the first decade after disturbance and did not peak until the third decade. Based on these patterns, we inferred that bitter cherry is not an obligate seed bank species. We did find viable seeds stored in the soil (25.0 ± 6.4 seeds/m2(mean ± SE) on sites with >600 live stems/ha) but concluded that historical disturbance intervals greater than the length of time seeds can remain viable in the soil have limited bitter cherry regeneration from a seed bank and, as a result, its distribution and abundance. Bitter cherry may play an increasingly important role in Pacific Northwest forests given the large areas of early successional habitat created by frequent timber harvests.Key words: H.J. Andrews Experimental Forest, seed bank, early succession, CART.

ISSN:0008-4026    

DOI:10.1139/b98-162

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

flo10-1 (superman-2)is a floral mutant inArabidopsis thalianathat normally produces female sterile flowers. This phenotypic aberration results from a combination of increased stamen number and reduced or abnormal carpels that are nonfunctional. The flowers offlo10-1contain two lateral and four median stamens, as seen in wild-type plants; however, they also contain several additional stamens. All stamen types have been examined with respect to frequency and location within the flower. The amount of pollen produced from each of the three types of stamens offlo10-1and the viability of this pollen were also examined and compared with wild-type (cv. Columbia) to determine the consequences of this mutation on male fertility. Both the lateral and median stamens offlo10-1and wild-type plants produced similar amounts of pollen per stamen and demonstrated no significant difference in viability. Per stamen, the additionals offlo10-1produced significantly less pollen than those of the laterals and medians. Furthermore, the pollen produced from these additional stamens was significantly less viable. Although less abundant and viable, pollen produced by additional stamens can effectively fertilize ovules, producing normal, healthy plants.Key words: pollen (viability, production), stamen, male fertility, flower development,Arabidopsis thaliana,flo10-1.

ISSN:0008-4026    

DOI:10.1139/b98-132

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Changes in respiration and ethylene production were characterized during maturation and ripening of saskatoon (Amelanchier alnifoliaNutt.) fruit. On a per fruit basis, respiration and ethylene production increased 78 and 400%, respectively, as fruit ripened on the plant and trends were consistent with those for climacteric fruits. When estimated on a fresh and dry weight basis, increased rates of ethylene production were still apparent during ripening; however, respiration rate declined. Trends in respiration rates and endogenous ethylene levels of harvested fruit of nine maturity classes, from immature green (class one) to fully ripe and purple (class nine), were consistent with those of fruit growing on the plant. Tissue prints showed that ACC (1-aminocyclopropane-1-carboxylic acid) oxidase was distributed throughout the pericarp of fruit at all nine maturity stages and that the enzyme was most concentrated in the immature stages on a per fruit basis. On a protein basis, ACC oxidase increased progressively with development of cv. Smoky fruit but remained relatively constant over the nine maturity classes of cv. Northline fruit. In contrast, ACC oxidase levels were relatively low in cv. Pembina fruit over the first four maturity classes, increased substantially as fruits developed from class four to five, then remained constant as fruit ripened to maturity class nine. Treating immature harvested Pembina fruit (maturity classes one to three) with ACC effected a 28- to 108-fold increase in ethylene production, compared with an average of only 7-fold for ACC-treated fruit of maturity classes four through nine. Preharvest treatment of class-three fruit with ACC induced ripening to maturity class eight within 5 days, while untreated fruit required 15 days to reach class eight. Vacuum infiltrating class four fruit with alpha-aminooxyacetic acid (AOA) or aminoethoxyvinyl glycine (AVG) inhibited ethylene production and color development substantially. The inhibiting effect of AOA on ripening was eliminated when fruit were infiltrated with equimolar concentrations of AOA and ACC. Cobalt, an ACC oxidase inhibitor, also inhibited ethylene production and ripening. Collectively, our results indicate that ethylene synthesis by preclimacteric fruit is limited by the availability of ACC, ethylene is responsible for initiating ripening, and thus, saskatoon fruit are climacteric.Key words:Amelanchier alnifolia, saskatoon, fruit ripening, ethylene.

ISSN:0008-4026    

DOI:10.1139/b98-101

出版商:NRC Research Press    

年代:1998

数据来源: NRC