摘要:

Rates of nonenzymic oxygen consumption by phosphohydroxypyruvate, hydroxypyruvate, and phosphoglyceric acid were compared. Relative rates of 1:20:0 were found at physiological pH. The results support the occurrence of phosphohydroxypyruvate metabolism that may contribute to photorespiration, and the presence of a serine biosynthetic pathway via phosphoserine in plants.

ISSN:0008-4026    

DOI:10.1139/b79-001

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Leciographa gallicolan.sp. (Patellariaceae) is described from galls of aspen (Populus tremuloidesMichx.) in western Canada.

ISSN:0008-4026    

DOI:10.1139/b79-002

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Rileyanov. gen. (Coelomycetes) is characterized by thick-walled plectenchymatous pycnidia, hypha-like, branched conidiophores, and holoblastic, distoseptate conidia with a simple apical appendage produced holoblastically from the inner wall. A single species,R. piceae, is described fromPicea sitchensis(Bong.) Carr. in coastal British Columbia, Canada.

ISSN:0008-4026    

DOI:10.1139/b79-003

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The acetylene reduction method was used to measure nitrogen fixation in soil cores of 16 cm diameter and 16 cm depth that included A and B horizon soil, roots, and decaying litter. Forty-three combinations of location and associated tree species were sampled. The rate of nitrogen fixation for most soil cores was 1 g N ha−1 day−1or less, which extrapolates to less than 0.2 kg N ha−1 year−1. The highest rates, with values of up to 23 g N ha−1 day−1, were observed in old fields being invaded by trees. The time course of acetylene reduction was usually linear for a 24-h period, most of the activity was in the upper 15 cm of soil, and the maximum rates were observed in midsummer. No significant nitrogen fixation was observed in preliminary measurements of decaying woody litter or of aerial surfaces of trees and rocks. It is suggested that nitrogen fixation is not a significant input of nitrogen for the forests studied. If so, there may be significant unrecognized nitrogen inputs to forests, such as dry absorption of ammonia from the atmosphere.

ISSN:0008-4026    

DOI:10.1139/b79-004

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Seasonal changes in the density of epilithic algae were determined from June 1975 to November 1976 at three sites on the north shore of Great Slave Lake. Densities increased rapidly in May immediately after the disappearance of ice, showed only small fluctuations during the summer, and waned during October. Microscopic algae, mainlyFragilaria capucina, Gomphonema olivaceum, G. ventricosa, Cymbella ventricosa, and other diatoms, reached peak abundance (2 × 109 μm3/cm2) on irregular occasions (July, September, October) throughout the growing season. However, filamentous algae, mainlyUlothrix zonata, reached maximum densities (60 mg/cm2dry weight) during July of both years.Additional survey collections of epilithic algae were made at 14 sites in the east arm of the lake during June and July of 1975. The most common species includedTabellaria flocculosa, Rhopalodia gibba, Cymbella angustata, C. microcephala, Anomoeoneis vitrea, Achnanthes minutissima, andUlothrix zonata. Algal densities were considerably less than those recorded from the north shore, a reflection of lower nutrient and alkalinity levels. Maximum abundances for microscopic and filamentous algae were 1.05 × 109 μm3/cm2and 4.1 mg/cm2respectively.

ISSN:0008-4026    

DOI:10.1139/b79-005

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Three large thalli of the saxicolous lichenParmelia cumberlandia(Gyeln.) Hale were subdivided. Portions were relocated to new sites within southern Ontario where they were left for a period of 1 year. At the end of the transplant period lichen substances in young tissue at the transplant sites were compared quantitatively with those produced at the original collection site. Changes were observed with respect to one minor unknown substance, but the depsidones and usnic acid were unaffected either qualitatively or quantitatively. Environmental differences of the magnitude tested were insufficient to cause major changes in lichen chemistry.

ISSN:0008-4026    

DOI:10.1139/b79-006

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

After ageing in water for 4 to 5 h, the permeability of excised squash hypocotyl sections to urea, as measured in hypotonic solutions, had declined to about 50% of freshly excised tissues. This degree of change was common to several members of the cucurbit family. The permeability change was relatively temperature insensitive and was not closely linked to segment length. It was unaffected by puromycin, cycloheximide, and actinomycin D. Adenosine phosphate compounds, indole-3-acetic acid, sulfhydryl reagents, and 0.5 mMCaSO4were also ineffective in altering the course of permeability change. However, the exposure of sections to osmotica (mannitol, glycerol, KCl) during ageing, at concentrations close to those of solutes found in the apparent free space of squash hypocotyls, significantly inhibited the decline of urea permeability. Once the decline in hypotonic solutions was expressed, it was not reversed by incubation in isotonic solutions in contrast with the short-term effects of osmotica on permeability in freshly excised sections. Apparently, the ageing-dependent decline in urea permeability by squash hypocotyl cells is the expression of a long-term osmotic regulatory process (irreversible) which complements the functioning of a short-term osmotic control system (reversible).

ISSN:0008-4026    

DOI:10.1139/b79-007

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

An undescribed Hyphomycete occurring on leaf litter ofGlycosmis cochinchinensisPierre, collected at Tambaram, near Madras, India, is described and assigned to a new genusSopagrahaas a new speciesS. sibika.

ISSN:0008-4026    

DOI:10.1139/b79-008

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Host–-parasite interfaces in leaves of a susceptible barley cultivar inoculated withPyrenophora tereswere studied using light and electron microscopy. Entry into the host rarely occurred through stomata, normal entry was by penetration into epidermal cells. Disruption of cell contents was evident in all initial penetration sites. After penetrating the epidermal cell, the fungus produced a large infection vesicle which gave rise to one or sometimes two intracellular hyphae. Hyphae spread down through the leaf tissue intracellularly for one or two cell layers and intercellularly thereafter. A septum, coincident with the external epidermal cell wall, was present in the infection peg located between the appressorium and the vesicle. Prior to leaving the epidermal cell, hyphae swelled to produce appressorium-like structures. These hyphae were sometimes septate at the point of exit. At sites where the infection had penetrated only four or five cell layers deep, the cellular contents of the mesophyll cells were relatively unaffected despite the presence of intercellular hyphae. However, when hyphae occasionally penetrated a host cell, gross disruption of their contents was apparent.

ISSN:0008-4026    

DOI:10.1139/b79-009

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The zoospore ofPhlyctochytrium plurigibbosumBarr is globular to amoeboid while swimming and posteriorly uniflagellate. Mitochondria are in the posterior and are petal-like in their arrangement. The nucleus and one or more lipid globules are in the centre to anterior part of the cell. Morphologically, microbodies are intimately associated with lipid globules and loosely associated with mitochondria. There is a conspicuous double membrane system of smooth endoplasmic reticulum, and free ribosomes are dispersed throughout the cytoplasm. Microtubules radiate into the zoospore body from the proximal face of the kinetosome.

ISSN:0008-4026    

DOI:10.1139/b79-010

出版商:NRC Research Press    

年代:1979

数据来源: NRC