摘要:

The vegetation of the area east of the Klutlan Glacier in the St. Elias Mountains is described with the methods of European phytosociology. Four major vegetation types are recognized:Picea glaucaforests,Populus balsamiferaforests,Betula glandulosashrub–tundra, andDryas integrifoliatundra.The modern pollen assemblages deposited in these vegetation types are determined by pollen analysis of surface moss polsters, lake muds, and moss samples from sedge swamps. Numerical analyses of the surface spectra indicate that spectra from theDryastundra and from thePopulusforests are distinctive in their pollen composition. The variation in the percentage pollen content of samples from thePiceaforests and the shrub–tundra is so great, even when spectra from a single sample type are considered, that no reliable distinctions can be made in modern pollen spectra from these two community types.

ISSN:0008-4026    

DOI:10.1139/b77-270

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

AM-toxin I (4 μg/ml), a host-specific toxin ofAlternaria mali, caused permeability changes in susceptible apple and Nijisseiki pear leaves within 5 min of treatment. The first effect of the toxin appeared on plasma membranes of susceptible apple cells. One hour after toxin treatment, slight invaginations were evident in plasma membranes near plasmodesmata. Six hours after treatment, the spaces between cell wall and invaginated plasma membrane contained lomasome-like vesicles, membranous fragments, and desmotubules extending from plasmodesmata. The membranous materials appeared to originate from the plasma membrane. Thirty-one hours after treatment, necrotic cells of susceptible leaves showed the general disruptions of cellular membranes which might be caused by secondary effects of the toxin. The similar changes of plasma membrane and plasmodesmata also were found in Nijisseiki pear cells treated with AM-toxin I (4 μg/ml) for 1 h and 6 h. The invaginations of the plasma membrane at plasmodesmata were the first ultrastructural modifications in the toxin-treated Nijisseiki cells. AM-toxin I did not affect the ultrastructure of resistant apple and Chojuro pear cells. These results indicate that the initial sites for the toxin may be on the plasma membrane of the susceptible apple cells. Furthermore, the results suggest that the plasma membrane modifications are associated with permeability changes in the toxin-treated, susceptible plant cells except for original host cells treated with the toxin.

ISSN:0008-4026    

DOI:10.1139/b77-271

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Ascospores ofHypoxylon cycliscum, H. flosculosum, H. sulcatum, H. scriblita, H. melanaspis, H. heterostomum, H. tinctor, H. hemisphaericum, andH. punctulatumhave been depicted as having smooth walls. Scanning electron microscopy reveals the walls of ascospores of these species to be intricately ornamented. The possible taxonomic significance of these observations is discussed.

ISSN:0008-4026    

DOI:10.1139/b77-272

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The protein, lipid, and fatty acid composition of the thylakoid membrane system of western hemlock (Tsuga heterophylla(Rafn.) Sarg.) chloroplasts was determined. Linear gradient slab gel electrophoresis of SDS-solubilized membrane protein preparations from the thylakoid system and its photosystem I (D144) and II (D10) subfractions resolved 32 protein bands. Density analysis of electrophoretic patterns accompanied by molecular weight determinations distinguished complex I at 63 kilodaltons and complex II at 23 kilodaltons.Sequential extraction of the thylakoid pellet in acetone - ethyl ether (4:1, v/v) and chloroform–methanol (2:1, v/v) followed by gel filtration on lipophilic Sephadex LH-20 provided two major lipid fractions. Qualitative thin-layer chromatography using lipid standards and colorimetric assays revealed the presence of monogalactosyl diglyceride, digalactosyl diglyceride, sulphoquinovosyl diglyceride, phosphatidyl glycerol, phosphatidyl choline, and phosphatidyl inositol. The concentration of each glycerolipid in micromolars per gram fresh weight of needle tissue was 11.16, 9.90, 6.18, 5.25, 3.16, and 2.32, respectively.The fatty acid contingent of each glycerolipid was determined by gas–liquid chromatography using 15% HI–EFF–IBP on Chromosorb W (100–200 mesh). Trimethyl(α, α, α-trifloro-m-tolyl)ammonium hydroxide was used as the 'on-column' active methylating agent. The following fatty acids were present at detectable concentrations in each of the glycerolipids: palmitic (16:0), palmitoleic (16:1), stearic (18:0), oleic (18:1), linoleic (18:2), linolenic (18:3), and 11-eiconsenoic (20:1). The major fatty acids of the phospholipids were 16:0 and 18:1, while the predominant fatty acids of the glycolipids were 18:3, 18:1, and 16:0.Western hemlock thylakoid membrane protein patterns appeared remarkably similar to those demonstrated in numerous plant and algal systems. On the other hand, thylakoid glycerolipids and their respective fatty acids, while qualitatively similar, revealed significant quantitative differences from values reported for herbaceous species.

ISSN:0008-4026    

DOI:10.1139/b77-273

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Seedling emergence from organic and mineral soil layers was measured for nine study sites at the Acadia Forest Experiment Station near Fredericton, New Brunswick. The number of viable seeds showed a decrease from deciduous-dominated forest, to conifer-dominated forest, to organic soil study sites. Viable seed number varied from 3400/m2for a deciduous-dominated forest study site to zero for a bog study site. Most seeds germinated from the upper organic soil layers of all study sites and were predominantlyRubus strigosusMichx. After the germination experiment, ungerminated seeds, which showed no viability by the tetrazolium test, were separated from the soil. These seeds were almost entirelyBetulaspp. and seed numbers were as high as 4200–9400/m2for a deciduous-dominated forest. The applicability of the results to differing types of postdisturbance revegetation is discussed.

ISSN:0008-4026    

DOI:10.1139/b77-274

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The influence of edaphic and atmospheric conditions on the development of plant water stress, water absorption by roots, and transpiration was studied with 2-year-old seedlings of Monterey pine (Pinus radiataD. Don). The slope of the relationship of xylem pressure potential to transpirational flux density was influenced by root temperature. Increased root resistances (separated from viscosity changes of water) occurred at root temperatures of 12 to 13 °C and became more limiting for water absorption at lower temperatures. Transpirational flux density was not affected by root temperature because xylem pressure potentials were not sufficiently low to close stomata. However, at the end of 9- and 12-day drying cycles, transpiration was lower than in well watered controls as a result of stomatal closure. The relationship between xylem pressure potential and transpiration exhibited hysteresis after 9 days of drying, but hysteresis was minimal upon rewatering or in unstressed control plants.

ISSN:0008-4026    

DOI:10.1139/b77-275

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Cytological studies on the vegetative hyphae of members of theRhizoctoniacomplex and basidial structures ofThanatephorus cucumeriswere performed with light and electron microscopy. Vegetative cells ofThanatephorusandWaiteaproved to be multinucleate, whereas those ofUthatobasidium, Ceratobasidium, Athelia. andBotryobasidiumare binucleate.Dolipore septa ofThanatephorus, Waitea, Uthatobasidium, andCeratobasidiumare visible with the light microscope when stained with aniline blue in glycerine. Ultrastructurally, pore caps in these genera consisted of two-layered unit membranes, forming cisternae with an electron-dense middle layer. Dolipore septa ofAthelia(S. rolfsii) andBotryobasidiumare not visible in aniline blue at the light microscope level. At the ultrastructural level, there was an additional cisternal membrane making up a pore cap of three membranes. The fine structure of nuclei, mitochondria, endoplasmic reticula, vacuoles, and other organelles in the basidial structures ofT. cucumeriswas essentially the same as in other basidiomycetes.Karyogamy of two haploid nuclei occurs in the young basidia ofT. cucumeris. The nuclear envelopes of both haploid nuclei break at their adjacent sides and fuse to form a diploid nucleus. After a short interphase, meiosis occurs. No leptotene was observed at prophase I, but a synaptinemal complex was evident and six pairs of chromosomes were observed throughout pachytene, diplotene, and diakinesis. The nuclear envelope disappears at metaphase I and a spindle appears. The second meiotic division is equational. Most of the mature and discharged spores are uninucleate.

ISSN:0008-4026    

DOI:10.1139/b77-276

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Frequency spectra of healthy plant storage tissue indicate that the tissue acts as a high-pass filter that attenuates low frequencies and allows high frequencies to pass through. During progressive deterioration of the tissue from infection of soft-rot bacteria, the frequency spectra indicated a loss in ability of the tissues to filter low frequency signals.

ISSN:0008-4026    

DOI:10.1139/b77-277

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Seedlings of 58 of about 150 species in the genusVicia(Fabaceae) were grown to the three-eophyll stage. A key, based on readily observable characters such as leaflet shape, number of leaflets per eophyll (seedling leaf), and nodal position of the first eophyll, is presented together with photographs of pressed seedlings. A marked tendency of species regarded as phylogenetically primitive to produce seedlings with bipinnate eophylls having leaflets broader than 2 mm is noted. Conversely, seedlings of more evolved species tend to have multipinnate eophylls with leaflets narrower than 2 mm.

ISSN:0008-4026    

DOI:10.1139/b77-278

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Botrytis cinereacauses a fast-spreading soft rot in lettuce that, under favorable conditions, completely destroys the tissues in less than 72 h. Within the first 24 h, the fungus penetrates the cuticle into the foliar parenchyma, destroying the cell wall and cellular content. Dictyosomes and mitochondria are altered and disappear first. Chloroplasts resist longer but are deeply modified with inflating and stacking of thylakoids, an increase in number of osmiophilic globules, and the disintegration of the plastidial membrane. Lomasomes and microbodies appear. Cell walls are made visible by Thiéry's technique. Bacteria invade dead tissues and seem to participate in a more complete destruction of the host and the fungus.

ISSN:0008-4026    

DOI:10.1139/b77-279

出版商:NRC Research Press    

年代:1977

数据来源: NRC