ISSN:0008-4026    

DOI:10.1139/b96-040

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

Hedgerows, woodland edges, oldfields, woodlots, and ditches constitute important habitats for wildlife (including plants). They also play an important role in connecting larger areas in the increasing fragmented rural landscape. The intensification of agricultural practices and increase in herbicide use in some regions of southern Quebec has caused the destruction of several habitats and has lowered habitat quality by reducing plant diversity. Nevertheless, the floristic composition of these habitats is poorly known. This study aims at evaluating the structural composition and describing the associated flora of such habitats in the St. Lawrence lowlands. Point-intercept and line-intercept methods were utilized. In total, the flora of the herbaceous, shrub, and tree layers of 35 woodlots, 54 woodland edges, 65 hedgerows, 49 oldfields, and 47 ditches have been described. The herbaceous layer of dominant species of hedgerows, oldfields, and ditches was relatively similar compared to woodlots. Although several annual and introduced species were found in disturbed habitats such as hedgerows, ditches, and oldfields, species associated to climax forests (sugar maple–hickory, basswood, and yellow birch forests) were also discovered in these habitats, a fact that enhances their value with respect to the maintenance of plant biodiversity in rural habitats.Keywords: hedgerow, woodland edge, oldfield, farm woodlot, ditch, conservation, biodiversity, agriculture.

ISSN:0008-4026    

DOI:10.1139/b96-041

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

Roots of salal (Gaultheria shallonPursh) collected from forest clearcuts were examined by light and scanning electron microscopy, and the ericoid mycorrhizal fungi were isolated and identified. Heavy colonization of typical ericoid mycorrhizae was present in and restricted to the first of the two layers of root cortical cells. Neither ectomycorrhizae nor arbutoid mycorrhizae were observed. In the field, over 85% of the roots and 90% of the cortical cells within colonized roots were colonized. One hundred and seventy-five of the 278 fungal isolates from salal roots formed ericoid mycorrhizae with salal in the laboratory, and these isolates were grouped into four species based on spore formation and cultural characteristics:Oidiodendron griseumRobak,Acremonium strictwnW. Gams, and two unidentified, nonsporulating fungal species. The association in the laboratory betweenA.strictumand salal was atypical in that the fungus improved the growth of salal seedlings but was slow to colonize roots and occasionally grew and even sporulated on the shoots. No differences in percent colonization or diversity of ericoid mycorrhizal fungi were found in salal growing on clearcuts from two different forest types.Keywords:Gaultheria shallon,Oidiodendron griseum,Acremonium strictum, ericoid mycorrhizal fungi.

ISSN:0008-4026    

DOI:10.1139/b96-042

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

The bright, yellow-green, ammonia-induced fluorescence of polyphenol compounds contained in the nonglandular hairs and within the epidermis ofOlea europaeaandQuercus ilexleaves was age dependent. Epifluorescence microscopic examination of transverse sections of leaves from both species showed that abaxial and adaxial epidermal layers emitted the characteristic green-yellow bright fluorescence only in late developmental stages, when a considerable decrease of the trichome density had already occurred. At earlier developmental stages, only the dense and thick trichome layer emitted the bright green-yellow fluorescence. In addition, the trichomes of young leaves ofOleaandQuercusresembled the glandular ones of other species morphologically and possibly functionally. These findings suggest that the protective role of the trichome against ultraviolet-B radiation damage and (or) other environmental factors is particularly significant during the early stages of leaf development and may be less important at later stages, when the protective role is taken over by the epidermis.Keywords: leaf hairs, phenolics, UV-B radiation damage, leaf development,Olea europaeaL.,Quercus ilexL.

ISSN:0008-4026    

DOI:10.1139/b96-043

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

The response of internal and external extracts of fresh arboreal lichens,Alectoria sarmentosa,Bryoria fuscescensandBryoria fremontii, and commercial usnic acid extracted fromUsneaspp. andCladoniaspp. on the growth of the AscomycetousGremmeniella abietinatypes was studied in vitro. Neither internal and external extracts of the three lichen nor usnic acid had strong inhibitive effect on the growth of either type A or B ofG.abietina. A slight stimulative effect due to the extracts was, however, detected: type B (isolate 12) grew faster on almost all media than type A (isolate 11), but great variation within isolates of both types existed suggesting that different types ofG.abietinamay have different responses to chemicals.Keywords:Gremmeniella abietina,Alectoria sarmentosa,Bryoria fuscescens,Bryoria fremontii, usnic acid, lichen toxicity.

ISSN:0008-4026    

DOI:10.1139/b96-044

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

Camptotheca acuminataplantations were established in southern Louisiana in an effort to provide raw plant materials for deriving camptothecins, compounds having antitumor activity. This study was conducted to evaluate the growth and camptothecin distribution within the trees. It was found that all plant parts contained camptothecins following 1 year of growth in the field. Branches, roots, and stems accumulated significantly higher concentrations of camptothecins than leaves. Bark was significantly higher in camptothecin concentration than wood. Younger and older tissues within a growing season were not significantly different in camptothecin concentrations. High correlation in camptothecin concentration was found between branch and stem, root and stem, and root and branch, whereas little correlation was observed between bark and wood, and leaf and any other plant component. Field-grownC.acuminatahas the observed characteristic of multiple current-year branching. The proportion of bark in term of dry weight and dimension decreased as trees increased in diameter. Dried shoots (bulk) contained 0.042% camptothecin, and dried roots (bulk) contained 0.051% camptothecin.Keywords:Camptotheca acuminata, medicinal plants cultivation, camptothecin content, camptothecin distribution, biomass.

ISSN:0008-4026    

DOI:10.1139/b96-045

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

We examined short-term (decadal) and long-term (millenial) processes of peat accumulation, and the links between them, in aSphagnumbog in continental Canada. A previously published model of bog growth was fitted to age profiles of the oxic acrotelm (surface, < 60 cm thick) and the underlying, anoxic catotelm (210 cm thick). Approximately 5300 years of accumulation were represented in a radiocarbon-dated core that extended to the base of the deepest part of the peat deposit. The model estimated that the overall rate at which material entered long-term storage in the catotelm was 60–66 g∙m−2∙a−1. Although the decay rate coefficient was near zero, the bog stopped accumulating peat within the past 1500 years, resulting from either a decrease in the rate of transfer of material from the acrotelm or an increase in the rate of decay of material at the top of the catotelm. The model of bog growth estimated recent inputs to the acrotelm (90–930 g∙m−2∙a−1) that were twofold higher than published field measurements of aboveground productivity, and decay rate coefficients (0.005–0.040 a−1) that were 10-fold lower than published litter-bag measurements of mass loss. The pattern of mass loss over time, approximated from nitrogen concentration data, deviated from the pattern predicted by exponential models of decay. Calculations of the balance between additions to and losses from the acrotelm suggest that the amount of material transferred to the underlying catotelm differs among microhabitats. Such spatial variability in short-term processes is incompatible with long-term processes determining the position of the acrotelm–catotelm boundary. We discuss the applicability of the model to continental peatlands and suggest ways to improve modelling of short-term autogenic processes.Keywords: peatland, peat accumulation, organic matter, decomposition, age profiles, mathematical

ISSN:0008-4026    

DOI:10.1139/b96-046

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

Callus derived fromDigitalis purpureahypocotils were grown during a 6-week period on solid Murashige–Skoog medium supplemented with 1 mg/L 6-benzylaminopurine, 0.01 mg/L gibberellic acid and 0.1 mg/L indole-3-acetic acid or α-naphthaleneacetic acid, with or without phenobarbital (40 mg/L). The presence of phenobarbital in the culture medium caused a reduction of the vacuole/cytoplasm ratio. At the same time, the chloroplastic volume fraction decreased in callus tissue cells grown in media supplemented with phenobarbital, while the mitochondrial volume ratio increased. Digitoxin content was enhanced in callus tissues, especially in those grown on indole-3-acetic acid medium supplemented with phenobarbital. The relationship between ultrastructure ofD.purpureacallus and digitoxin content is discussed.Keywords:Digitalis purpureatissue cultures, digitoxin, phenobarbital, mitochondria, chloroplast.

ISSN:0008-4026    

DOI:10.1139/b96-047

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

Plant growth responds to light quality, as evaluated by the red/far-red (R/FR) quantum flux ratio, and to the level of CO2.Pinus banksiana,Picea marianaandPicea glaucaseedlings were raised at 350, 700, or 1050 μL∙L−1CO2and high or low R/FR ratios and growth was measured over a 16-week growth period. Far-red rich light enhanced the whole plant and height relative growth rates ofPinus banksiana. The three species showed species specific responses in plant organ relative growth rates and partitioning ratios. On the basis of their biomass partitioning the species would be rankedPinus banksiana<Picea mariana<Picea glaucafor shade tolerance. In commercial operations, seedlings grown for outplanting are selected, in part, on the basis of plant form as described by the stem height/diameter ratio. More desirable ratios were obtained at ambient CO2concentrations forPinus banksianaandPicea marianain red rich light and forPicea glaucain far-red rich light.Keywords: seedling growth, light quality, CO2enrichmen

ISSN:0008-4026    

DOI:10.1139/b96-048

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

Pinus banksiana,Picea mariana, andPicea glaucawere grown at 350, 700, or 1050 μL∙L−1CO2and either high or low red/far-red quantum flux ratios. After a 16-week, long day growth period, seedlings were subjected sequentially to short daylengths, then short days with low temperatures. Various physiological parameters were determined at the end of each treatment phase to monitor how those treatments influenced the onset of seedling dormancy. After the long day treatments, high ratios increased the total chlorophyll content and reduced the original level of chlorophyll fluorescence and the shoot total nonstructural carbohydrate content in very shade-intolerantPinus banksiana. In shade-tolerantPicea mariana, high CO2levels caused the main effects on these parameters while neither light quality or CO2had significant effects on them in shade-tolerantPicea glauca. Short days and low temperature induced a proportional increase in the partitioning of total nonstructural carbohydrate to the roots in all species and produced other species and treatment-specific responses.Keywords: light quality, CO2enrichment, chlorophyll fluorescenc

ISSN:0008-4026    

DOI:10.1139/b96-049

出版商:NRC Research Press    

年代:1996

数据来源: NRC