摘要:

The taxonomic value of the presence of sarcodimitic tissues and derived tissues in the agarics was investigated. Basidiomata of only 15 genera of 153 agaric and bolete genera surveyed had sarcodimitic tissues. The family, the Xerulaceae, is recognized for these 15 lamellate, sarcodimitic genera along with 1 genus exhibiting modified tissues and 2 closely allied genera apparently lacking sarcodimitic tissues. It is hypothesized that they evolved convergently and then in parallel with members of the Tricholomataceae. Taxonomic difficulties arising from the apparent loss of the sarcodimitic tissues in evolutionarily advanced taxa within the Xerulaceae, such asMycenaandXerula, are discussed. Antibiotics with an (E)-β-methoxyacrylate moiety (strobilurins, oudemansin), which are potentially useful against cancer, with one possible exception are found only in a number of genera with sarcodimitic or derived tissues currently assigned to the Xerulaceae. Two new combinations are proposed:Cystolepiota pusillomyces(Peck) comb.nov. andFloccularia albolanaripes(Atk.) comb.nov.

ISSN:0008-4026    

DOI:10.1139/b87-214

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Image analysis was used to quantify size of endospermic starch granules in 39 species ofHordeum. A set of 279 samples, each with ca. 25 replicates, representing most species of the genus was analyzed by various multivariate techniques. Two groups can be distinguished. One group consisting of 6 species (H.vulgare,H.spontaneum,H.bulbosum,H.glaucum,H.murinum, andH.leporinum) is characterized by possessing granules greater than 35 μm in diameter and a bimodal distribution of all the sizes. The second group, consisting of the remaining 33 species, had granules less than 35 μm in diameter, unimodally size distributed. Univariate statistics for each species are summarized in box plots and bar diagrams. Some species can be uniquely identified. The usefulness of starch inHordeumsystematics is discussed.

ISSN:0008-4026    

DOI:10.1139/b87-215

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

This study compared how two tree species with different leaf life-spans differ in their adaptations to low nutrient availability in a Wisconsin bog. Seasonal patterns of foliar nutrient concentration, nutrient resorption, leaching loss to simulated rainfall, and growth efficiency were determined forLarix laricinaandPicea marianaduring 1983 and 1984. Concentrations of foliar nitrogen and phosphorus inLarixleaves increased slightly during summer; this was followed by strong autumnal resorption. Calcium concentration ofLarixleaves increased throughout the entire life-span of the leaves. Concentrations of nitrogen and phosphorus were highest in new (age-class 0)Picealeaves and declined with each successive leaf age-class, whereas calcium leaves increased in older leaf age-classes. Winter–spring resorption of nitrogen and phosphorus occurred from all age-classes ofPicealeaves; this was followed by a summer increase in foliar nutrient concentrations. Resorption of nitrogen was greater inLarixthan inPicea. There were no significant differences in phosphorus resorption or nutrient growth efficiencies between species. Foliar nutrient losses to leaching by artificial rainwater were less than 1% of the total foliar nutrient content. As there was no significant difference in the relative growth rates or growth efficiencies between the two species, the persistence of deciduousLarixin nutrient-poor bogs among species with longer leaf life-spans might be linked to its greater nitrogen conservation.

ISSN:0008-4026    

DOI:10.1139/b87-216

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

The patterns of branching and extension growth of vigorous saplings of eight JapaneseAcerspecies were studied in relation to gap sizes where they regenerate in late-successional forests. Three types were recognized: sympodial-spread type, elongate type, and monopodial-spread type. In the sympodial-spread type, long and short shoots do not occur, and the amount of extension growth is small. These characteristics are more adapted to producing an efficient photosynthetic surface area than height growth. Extension growth is determinate. Determinate species flush leaves simultaneously at budbreak, which ensures a long duration of photosynthesis in a year. This type regenerates in small gaps with its shade-tolerant growth mode. In the elongate type, long and short shoots occur, and the amount of extension growth is large. These characteristics are more adapted to height growth than producing an efficient photosynthetic surface area. Extension growth is indeterminate. Indeterminate species start rapid height growth earlier than determinate species. This type responds to the occurrence of gaps and regenerates in large gaps with this competitive growth mode. In the monopodial-spread type, long and short shoots do not occur, the amount of extension growth is large, and extension growth is indeterminate. This type regenerates in middle-sized gaps with a growth mode intermediate between the previous two types.

ISSN:0008-4026    

DOI:10.1139/b87-217

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

The infection process in four clones of eastern cottonwood susceptible or resistant to leaf rust caused byMelampsora medusaewas studied by light and electron microscopy. Infection was initiated by stomatal rather than direct entry. Typical dikaryotic haustoria were observed in all clones within 1 day of inoculation. Some healthy-appearing haustoria were observed in susceptible clones throughout the duration of the study, which was terminated during the initiation of uredial production. Incompatibility was expressed differently in the two resistant clones. In clone St 75, most haustoria and invaded host cells that were observed appeared necrotic within 2 days of inoculation. Cell wall appositions appeared during this time in cells adjoining necrotic host cells. Some infected cells disintegrated within 4 days of inoculation. Affected host cells of clone St 92, on the other hand, plasmolyzed during the first 2 to 3 days after inoculation. Necrotic host cells were not observed in this clone until the 4th day after inoculation. Hyphal ramification and host plasmolysis were extensive at 6 days after inoculation.

ISSN:0008-4026    

DOI:10.1139/b87-218

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

The seasonal growth ofLaminaria groenlandica(Laminariales, Phaeophyta) on the west coast of Vancouver Island, B.C., Canada, was investigated as a function of plant age, using plants maintained at a constant depth on rope structures. First-year plants, which become macroscopically visible in March, had a delayed seasonal peak of maximum blade size relative to the older year classes (April–May) which initiated growth in January. This resulted from the 1st-year plants' lower susceptibility to distal blade erosion and prolonged net growth season. All year classes obtained their greatest wet weight at the same time (July–August). For 1st-year plants, this represented a balance between blade erosion and elongation; for older plants, storage product synthesis and blade thickening and elongation balanced against erosion appeared responsible for determining maximum biomass. The 2nd-year class dominated the other year classes in blade dimensions and few plants survived their 3rd year of growth. The instantaneous growth rates ofL.groenlandicawere most closely associated with temperature, followed by photon flux density, and changes in growth rates were associated with temperature and salinity.

ISSN:0008-4026    

DOI:10.1139/b87-219

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Fifty-four samples of modern sediment from Banks Island and the Melville–Horton region of the Northwest Territories illustrate the major features of pollen deposition from the high to low arctic. Modern pollen deposition in the high arctic of Banks Island is characterized by up to 14% windblown tree pollen. Indicator taxa of the high and mid arctic includeOxyria(<5–23%), Saxifragaceae,Saxifraga oppositifolia, and Cruciferae (all up to 8%) andDryas(up to 3%). Arboreal pollen increases to 60% in low-arctic and subarctic samples. Pollen concentration decreases from between 3 500 and 20 000 in the low arctic to less than 5 000 grains/cm3in the high and mid arctic. Pollen spectra from the Late Glacial of northwestern Canada differ from those of the modern high and mid arctic not only by the absence of trees and shrubs but also in the relative proportions ofArtemisiaand of such indicator taxa asOxyriaand Saxifragaceae.

ISSN:0008-4026    

DOI:10.1139/b87-220

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

The morphological variation of seedlings from a single population ofPseudotsuga menziesiiwas examined and related to their maternal parentage (41 families) and speed of germination (selection) during the course of a common garden experiment. The largest source of variation among seedlings was attributed to within-family variation. Furthermore, within-family variable intercorrelations differed from family to family, suggesting that intrinsic causal factors are important to the generation and organization of variation. Pooled within-family variation was explored and shown to be related to the between-family variation. These results suggest that developmental and historical factors cannot be ignored in the interpretation and exploitation of sources of variation. Such considerations identify limitations to Neo-Darwinian explanations and suggest reappraisal of progeny trials with respect to these issues. The results also pose limitations to our interpretations of genetic similarity on the basis of multivariate morphological data.

ISSN:0008-4026    

DOI:10.1139/b87-221

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Species boundary clustering in zoned vegetation was examined along six wetland–upland coenoclines from four prairie marshes in eastern South Dakota that differed in size, permanence, water quality (salinity), topography, and exposure to waves. Vegetation structure and composition were measured from small, contiguous quadrats running through concentric vegetation zones. Rates of vegetation change along coenoclines were estimated using direct gradient analysis, detrended correspondence analysis, and a statistical technique that detects clustering of species' borders. All wetlands exhibited visually distinct zones, but quantitative analysis revealed that vegetation fomed a virtual continuum along the gradient in small wetlands, while near the shorelines of large wetlands both vegetation composition and structure were sharply discontinuous between marsh and meadow zones. This lower border of the meadow zone apparently was sharpened by exposure to waves and ice scour. The upper meadow zone border with prairie vegetation was less distinct but coincided with a sharp change in topography and in subsoil texture. Interspecific competition appeared less important than physical environmental factors in affecting zonation discreteness. The meadow–prairie zone contact approximates the upper limit of influence from wetland processes and is proposed as the wetland–upland border.

ISSN:0008-4026    

DOI:10.1139/b87-222

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Selected fungi recovered from the phylloplane of lettuce were assayed, usingin vitroandin vivotechniques, to determine their effectiveness as antagonists of ascospores of the lettuce drop pathogen,Sclerotinia sclerotiorum. On leaf discs,Trichoderma viride,Alternaria alternata, andEpicoccum purpurascenssignificantly reduced ascospore germ-tube elongation by 34.2, 60.6, and 38.3%, respectively. On whole plants, these three fungi significantly reduced infection by 40–93.3%. Isolates ofCladosporium cladosporioidesand a red yeast inhibited ascospore elongation significantly in thein vitroleaf disc assay but failed to provide significant protection against infection byS.sclerotiorumin thein vivowhole-plant assay. Observations with the scanning electron microscope indicated that hyphae ofT.virideandA.alternatacame into close contact with ascospores on the leaf surface, suggesting parasitic relationships. Hyphae ofE.purpurascensdid not come into direct contact with ascospores and inhibition may have been due to production of antifungal compounds.

ISSN:0008-4026    

DOI:10.1139/b87-223

出版商:NRC Research Press    

年代:1987

数据来源: NRC