摘要:

To clarify the limits betweenH.depressum(Scribner & Smith) Rydberg and its close and remote allies,H.intercedensandH.pusillum, respectively, we carried out morphological and cytological examinations and various statistical analyses including classifactory discriminant analysis, canonical discriminant analysis, and logistic discrimination. We concluded thatH.depressum, a tetraploid species, can usually be morphologically separated fromH.intercedens, a diploid species with which it is most frequently confused, by the maximum width of the lateral lower glumes. Those ofH.depressumare 0.1–0.5 mm wide, whereas those ofH.intercedensare 0.4–1.3 mm wide. Very few specimens will fall in the area of overlap between the two species. In these cases morphological identification can be ascertained by the lodicules, which inH.depressumhave an obvious and glabrous side lobe, whereas if there is a lobe inH.intercedens, it is rather small and beset with hairs at the margins. Populations ofH.depressumare often large and occur in the intermontane region of northern and central California, whereas those ofH.intercedensare typically small and occur along the coast of south California and Baja California. These two species are sympatric to a small degree, whereasH.pusillumdoes not occur in south and Baja California but is found throughout the United States and a few adjacent places in Canada. Other morphological and statistical findings are discussed.

ISSN:0008-4026    

DOI:10.1139/b88-064

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Exposure of cold-hardened seedlings of a range of winter cereals (11 winter wheats, 1 winter barley, and 1 winter rye) to a light intensity of 100 μE∙m−2∙s−1during ice encasement at −1 °C markedly increased survival in comparison with that in dark ice encasement. Cold hardiness of 'Dover' winter barley and 'Fredrick' and 'Norstar' winter wheats was significantly greater after a short period of light ice encasement than dark ice encasement. Less ethanol and more CO2accumulated in plant crowns in light than dark ice, and lactic acid accumulated in the early days of ice encasement but was little influenced by light. There was greater utilization of total nonstructural carbohydrate in the crown in dark, than in light, and greater utilization of total nonstructural carbohydrate in ice than in air at −1 °C. Considerably less oxygen was consumed by plants in light than in dark ice, while leaves in aqueous solutions at −1 °C evolved significant levels of O2in light but consumed O2in the dark. It is proposed that the changes in metabolic components in light are associated with low-temperature photosynthesis, which provides cellular oxygen and greater levels of energy in support of cell maintenance in plants during ice encasem

ISSN:0008-4026    

DOI:10.1139/b88-065

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Erigeron salishiiG. W. Douglas & J. G. Packer, n.sp., a morphologically distinctive species from southwestern British Columbia and northwestern Washington, is described, illustrated, and compared withE.compositusvar.discoideus.

ISSN:0008-4026    

DOI:10.1139/b88-066

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Copper and Zn concentrations in raw humus were elevated > 400 and > 80 times, respectively, near an old and a new foundry emitting Cu and Zn but virtually no SO2. Effects on the vegetation were most evident in the ground layer. Four response stages were recognized. (i) Common mosses of mature coniferous forest (Pleurozium schreberi,Hylocomium splendens,Ptilium crista-castrensis,Dicranum polysetum) began to decrease in cover where the Cu and Zn levels in the tissues were 3–5 and 2 times those measured at remote sites, respectively, (ii) Lichens typical of mature dry forest communities (Cladoniasubgen.CladinaandC.uncialis) were reduced in cover. (iii) Pioneers typical of successional communities (especiallyCladoniasubgen.Cladonia) increased slightly in cover, while tolerant mosses retained their cover, (iv) Even the tolerant mosses and lichens disappeared, except forPohlia nutans. The occurrence of epiphytic lichens decreased.Hypogymnia physodessuffered a reduction in cover and thallus size. The grassDeschampsia flexuosatended to increase somewhat towards the foundries, but the other field-layer species were unaffected. However, much deadDeschampsia flexuosahas been observed recently close to the new foundry. Environmental variables modified the response of the vegetation to the pollution. Deterioration of the ground layer makes the polluted, thin soil prone to erosion.

ISSN:0008-4026    

DOI:10.1139/b88-067

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Defoliation of dormant native plants often results in reduced plant height and productivity when growth resumes. To identify a possible mechanism for this effect, three experiments were conducted to test the hypothesis that the response is determined by a modified environment at the crown. Rough fescue (Festuca scabrellaTorr.) sod was removed from native grassland during dormancy and transplanted into pots. In the first experiment, clipped plants were subjected to radiation densities (PAR) varying from 80 to 360 μE∙m−2∙s−1. In the second experiment, plants were grown in five soil water contents: 100, 100–80, 100–60, 100–50, and 100–40% of field capacity. In the third experiment, plant response to two levels of each factor (PAR, water, and temperature, 20:10 or 15:5 °C (light:dark)) were examined in relation to litter removal by clipping or burning. Plant response was measured as plant height, number of tillers, and tiller weight. Plant growth was most responsive to soil water deficits and least responsive to temperature. Plant height and tiller weight were 32% less than the control (field capacity) when soil water content was allowed to decline to 60% of field capacity. Plant height was decreased, but not tiller density, with increased PAR. Removing standing litter by clipping resulted in increased tillering (14%) and reduced plant height (15%). Since soil water was not limiting, the effect of clipping was attributed to increased PAR near the crown following litter remo

ISSN:0008-4026    

DOI:10.1139/b88-068

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

The nitrogen cycle of a small, forested,Sphagnumpeatland in northern Minnesota was studied for 4 years. Hydrologic inputs and outputs (atmospheric deposition, upland runoff, streamflow) were monitored for4 years, and annual uptake of N by vegetation was measured over a 3-year period. Microbe-mediated processes of nitrogen fixation and mineralization were measured in the laboratory and field, and accumulation rates of N within the peatland were measured in dated peat cores. Aerobic heterotrophs appear to be the dominant agents of N fixation at this site. Rates of N fixation decrease rapidly below the surface. Perhaps limited by moisture and low pH, N fixation (0.5–0.7 kg∙ha−1∙year−1) is a minor input to the bog relative to the input from atmospheric deposition (10.4 kg∙hg−1∙year−1). The bog is a large sink for N with approximately 65% of inputs retained. Annual turnover of N (66 kg∙ha−1) is much larger than the total input (14.6 kg∙ha−1). This large turnover is achieved by rapidly cycling a relatively small pool of N in the aerobic layers of peat. Plant uptake is closely coupled to mineralization such that losses from the system in runoff are small. However, 7 to 12 kg N∙ha−1∙year−1is buried in anaerobic peat and rendered unavailabl

ISSN:0008-4026    

DOI:10.1139/b88-069

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Manual assembly of large morphometric data sets for investigations in population biology and biosystematics is extremely time consuming. Automated image handling allows rapid and accurate data collection and in addition makes it practicable to uncouple image acquisition and shape description. Variation can be characterized flexibly when these two phases of "scoring" are separated. Different descriptor systems can be used to describe a set of stored outlines, without having to return to the original objects. This paper introduces an integrated automated outline handling system and compares the relative performance of shape descriptor systems based on (i) landmark and perimeter measurements, (ii) chain codes, (iii) elliptic Fourier coefficients, and (iv) moment invariants. These methods were assessed by their ability to characterize the pattern of variation in a set ofBetulaleaf silhouettes with a hierarchical sample structure that allowed variation to be partitioned into within-tree, between-tree and between-species components. The descriptor systems using landmark and perimeter distances, elliptic Fourier coefficients, and moment invariants performed well, not only reflecting differences between species and between individual trees but also recovering the two-dimensional geometry of the within-tree sample positions. The elliptic Fourier method is judged to have performed best; the chain-code descriptor system performed poorly.

ISSN:0008-4026    

DOI:10.1139/b88-070

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Quince (Cydonia oblongaMill.) seed epidermis was examined cytologically during its development. Three developmental phases were delimited: immaturity, transition to maturity, and maturity. These cytological phases corresponded with phases of competence to release hydrated mucilage on wetting, immature tissue being completely incompetent and mature tissue fully competent. Growing cells of immature tissue were vacuolate and thin walled. By contrast, protoplasts of nongrowing mature epidermal cells had contracted to a remnant and been replaced by periplasmic deposits. Within these deposits, surrounded by amorphous material, were massive arrays of widely spaced microfibrils arranged helicoidally. In the oldest sample examined, periplasmic material appeared to be spewing through the broken outer walls of some cells. The periplasmic material is interpreted to be prerelease mucilage, which progressively fills the periplasm during a brief transitional phase. It seems that amorphous periplasmic material is deposited initially and microfibrils later intermingle with it. At some stage during filling of the periplasm, the microfibrils begin to organize, ultimately becoming helicoidal. Orderliness seems to begin in the central region of the periplasmic pool, not at its edges. It is proposed that nucleation of liquid crystalline helicoidal arrays occurs in the periplasm and that these arrays remain fluid until their disintegration during release as a result of hydration.

ISSN:0008-4026    

DOI:10.1139/b88-071

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Forty-two anatomical and exomorphological characters from 16 species and 2 varieties ofFestucanative from Patagonia were numerically analyzed. Principal components analysis together with cluster analysis arranged 14 taxa into 5 groups (F.tunicataandF.acanthophylla, group 1;F.monticola,F.thermarum, andF.scabriuscula, group 2;F.pallescens,F.p. var.scabra, andF.kurtziana, group 3;F.gracillimaandF.ventanicola, group 4; andF.contracta,F.rubravar.simpliciuscula,F.pyrogea, andF.magellanica, group 5;F.argentina,F.purpurascens,F.cirrosaandF.pampeanawere not included in any of the groups). Cluster analyses performed on either vegetative or reproductive characters showed that they alone are not enough to summarize variation among these taxa.

ISSN:0008-4026    

DOI:10.1139/b88-072

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Eleven of the 13 North American species ofXeromphalinaare reported from Canada. A key to 14 North American and northern Eurasian species is given. Type specimens for 9 names were examined. In Canada, subgenusHeimiomycesis represented by two species:X.tenuipes(Schw.) Smith (sect.Heimiomyces) andX.fulvipes(Murr.) Smith (sect.Fulvipes). SubgenusXeromphalinais represented by sectionsXeromphalinaandMutabiles.Xeromphalina brunneolaMiller andX.campanella(Batsch: Fr.) Kuhner & Maire are circumboreal species documented from across Canada.Xeromphalina kauffmaniiSmith occurs in southern Quebec, Nova Scotia, Costa Rica, the eastern United States, and in Japan. SectionMutabilesstat.nov. is completely revised based on pigmentation of the pileipellis, on the distribution and types of pileocystidia, and on the pigmentation of the stipe, in addition to characters used previously in the genus. The term "circumcystidia" is coined for pileocystidia largely confined to a band around the pileus margin. In North America, the nameX.cauticinalis(Fr.) Kühner & Maire frequently has been misapplied toX.cornui(Quél.) Favre, a common, widespread species in Canada.Xeromphalina fraxinophilaSmith is reported from across Canada and the United States and in Eurasia. The nameMarasmius cauticinalisis neotypified. In North AmericaX.cauticinalisssp.cauticinalisoccurs in western areas.Xeromphalina cauticinalisssp.pubescentipes(Peck) comb. et stat. nov. occurs in eastern areas in North America, in Japan, and together with ssp.cauticinalisin Europe.Xeromphalina parvibulbosa(Kauff. & Smith) comb.nov. occurs across North America.Xeromphalina cirrissp.nov. from montane or boreal coniferous forests floors in British Columbia, Ontario, Colorado, Idaho, New Mexico, Oregon, Utah, Washington, and Wyoming andX. campanelloidessp.nov. from coastal British Columbia and Washington, and eastern montane New York and Quebec, on coniferous logs, are described. Rhizomorphs are formed by all Canadian species exceptX.tenuipes.

ISSN:0008-4026    

DOI:10.1139/b88-073

出版商:NRC Research Press    

年代:1988

数据来源: NRC