摘要:

Variations in the morphology ofChlamydomonas segnishave been investigated under various cultural conditions. In cultures maintained at 250 ft-c and 15 °C without aeration, this alga assumed the form of aGloeocystis, whereas in aerated mass-culture grown at 25–30 °C and 1000 ft-c the motile stage showed close similarity to the genusGloeomonas. Cells ofC. segnisgrowing in synchronous culture under high light intensity (1000 ft-c) and supplied with 5% CO2in air (v/v) reproduced asexually to form four zoospores, whereas cells provided with air produced only two zoospores. When zoospores developed in light their increase in cell volume was not accompanied by an increase in the length of their flagella. Homothallic anisogamous sexual reproduction could be demonstrated under conditions unfavourable for growth. Ultrathin sections of cells developed in light revealed a lobate, cup-shaped chromatophore. The mitochondria possessed irregular profiles with constrictions and were mainly located on the outer surface of the chloroplast. Intracytoplasmic, convoluted inclusions and interthylakoidal crystals have been observed. Microbody-like organelles, similar to those in plant leaf tissue, occurred in autotrophically grownC. segnis.

ISSN:0008-4026    

DOI:10.1139/b73-011

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Areas of boreal forest in the Clay Belt of northern Ontario, burned at a range of times from 0 to 57 years before the present, were examined. The range of vegetation present was sampled by means of a number of plots in each area. A simple test of heterogeneity, based on the number of significant correlations between species, was applied to the data from each area. Vegetation samples and species were each classified into nonexclusive groups, and the properties of the groups explored. Maturity weightings, based on the age of the site at which each species was first detected, were calculated for each sample.The results of analyses indicated the presence of four stages in the succession: (a) initial heterogeneity; (b) early phase; (c) heterogeneous phase; and (d) late phase. Initial heterogeneity, attributable to burning intensity, persists for a year, but is succeeded by a more homogeneous phase dominated by species which survive the fire in various ways. The heterogeneous phase is dominated by environmentally differentiated mosaic elements; it is succeeded by the late phase as a canopy develops and as ephemeral species, which colonized the disturbed area, disappear. The late phase is dominated by jack pine in sandy areas and by black spruce in peaty areas.There is evidence that the changes from one phase to the next are spatially heterogeneous because some sites mature more rapidly than others. The paths of succession at different sites within an area may differ, but there is convergence to one of the two main vegetation types in the late phase. The late phase types are differentiated at a much larger scale than the seral mosaic elements.

ISSN:0008-4026    

DOI:10.1139/b73-012

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Cycloheximide inhibits the incorporation of acetate-2-14C into protein and into asparagine in corn root tips. It also causes an accumulation of glutamine and, over a concentration range of 0.4 to 5.0 μg/ml, a transient accumulation of the neutral and basic amino acids. In mature sections, cycloheximide inhibits protein synthesis but causes an increase in the incorporation of radioactivity into both glutamine and asparagine. Azaserine, a glutamine analogue, also inhibits the formation of asparagine in root-tip sections but has only a minor effect on protein synthesis. In mature root sections, there is an accumulation of glutamine but no effect on asparagine formation when azaserine is used. Glutamine additions to root tips or mature root sections affect neither asparagine formation nor protein synthesis. We conclude that cycloheximide is behaving as a glutamine analogue in its effect on asparagine biosynthesis, and that its effect as a glutamine analogue is lost as cells mature.

ISSN:0008-4026    

DOI:10.1139/b73-013

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

The myxomycetePerichaena vermicularishas been fixed with formaldehyde–glutaraldehyde at various stages of fruiting and the distribution of β-glycerophosphatase determined at the electron microscope level using a modified Gomori procedure. Specimens from various stages of the developing fruiting body when incubated for 70–105 min at 39 °C in a medium containing β-glycerophosphate showed good localization of reaction product. High β-glycerophosphatase activity was localized in single-membrane-bound vacuoles at all stages of fruiting body formation. These vacuoles are similar to lysosomes of animals, higher plants, and fungi in that they are surrounded by a single membrane, contain cell components at various stages of disintegration, and have a high acid phosphatase activity.Reaction product was also localized in the walls of mature spores and was variably associated with nuclei and mitochondria. Most probably the staining of some nuclei and mitochondria is a lead absorption artifact.

ISSN:0008-4026    

DOI:10.1139/b73-014

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Young red pine trees were supplied with14CO2through a branch in the third whorl. Darkening or removal of all other needles caused a major diversion of14C to the expanding terminal shoot. Defoliation had a much greater effect than darkening. The diversion can be only partially explained on the basis of removal of competing sources of carbohydrate. Use as well as distribution of labeled photosynthate was affected by the treatments.

ISSN:0008-4026    

DOI:10.1139/b73-015

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

The conidial state ofXylaria johorensisis described from pure culture. Because of a close morphological similarity between both the perfect and conidial state of the fungus and species ofPoronia, it is transferred to that genus.

ISSN:0008-4026    

DOI:10.1139/b73-016

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Developing synchronous cells ofScenedesmus obtusiusculusChod. were investigated during the 15-h light period of the 24-h life cycle. Measurements were made of photosynthesis and of the chlorophyll, carotene, nucleic acid, and protein content, including intracellular phosphorus.Photosynthetic oxygen evolution (μmol/mg chlorophyll) increased during the early growing stage and declined gradually in the older cells. Chlorophyll, carotene, protein, ribonucleic acid, and ribonucleic acid phosphate of these cells increased during the growth phase (dry weight basis) and declined in the sporulating phase, whereas the deoxyribonucleic acid and deoxyribonucleic phosphate decreased during the growth phase. Deoxyribonucleic acid increased slightly in the sporulating phase, but deoxyribonucleic acid phosphate remained relatively constant during this period. When calculated on a per cell basis, ribonucleic acid and ribonucleic acid phosphate increased steadily throughout the period of observation, whereas deoxyribonucleic acid and deoxyribonucleic acid phosphate remained constant during the first 5 h and then increased gradually. Analysis of the intracellular distribution of phosphorus(dry weight basis) revealed that methanol-soluble (lipid) phosphorus decreased steadily with cell growth, whereas the content of acid-soluble phosphorus and ethanol–ether-soluble (lipid) phosphorus fluctuated markedly. The pH of the culture medium increased concomitantly with cellular development during the light period.

ISSN:0008-4026    

DOI:10.1139/b73-017

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

The influence of calcium supply on the chlorophyll, carotene, nucleic acid, and protein content inScenedesmus obtusiusculusChod. was investigated. Evidence showed that upon addition of calcium-starved cells to a culture medium containing calcium, the levels of all these components increased slowly for 15 h. During the next 33 h chlorophyll and carotene content increased more rapidly, and the chlorophylla:bratio also increased. During this growth period, both RNA and protein content increased linearly whereas DNA content did not increase on a dry weight basis throughout the period of observation.

ISSN:0008-4026    

DOI:10.1139/b73-018

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Mycoarctium ciliatum, a coprophilic discomycete, was isolated from deer dung and grown on nutrient medium. Single ascospore cultures form ascocarps within 2 weeks. Typically, apothecial formation is associated with two to six well-developed ascogonia; ontogeny of the ascogonium is discussed. Excipulum and paraphyses both originate from the basal cells of the ascogonium and appear before the ascogenous system. The ascogonium also produces septate ascogenous hyphae of two types, primary and secondary. Asci form directly from ascogenous hyphal tips or via croziers, and may or may not be delimited by a septum from the subtending element. Conjugate division in ascogenous hyphae is implied by the presence of nuclear quartets. There is some evidence that asci may occasionally arise from paraphyses.

ISSN:0008-4026    

DOI:10.1139/b73-019

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Good saprobic growth of primary and established cultures ofMelampsora lini(Ehrenb.) Lév., race 3, was obtained on chemically defined media containing modified Knop's minerals, various trace elements, 5% sucrose, and aspartic acid. Cysteine, cystine, and glutathione had to be added to the base medium singly or in combination. Alanine and methionine, added to minerals and sucrose, supported only sporadic and slow growth of primary flax rust cultures; and established cultures started on media containing more complex amino acid mixtures did not survive on the alanine–methionine medium. Types and concentrations of essential amino acids determined the rate of mycelial growth.

ISSN:0008-4026    

DOI:10.1139/b73-020

出版商:NRC Research Press    

年代:1973

数据来源: NRC