摘要:

The little known chrysophycean genusSpiniferomonasTakahashi is an important component of the phytoplankton of many Ontario lakes. Ten species have been found, only three of which (S.trioralisTak.,S.bourrelliiTak., andS.andersoniiGreen) are known previously from North America. Two species (S.andersonii,S.conicaTak.) are shown to be synonymous with the type species,S.bourrellii. Two new species are described (Spiniferomonas takahashiiandSpiniferomonas serrata) and a revised key to all known species is presented.Spiniferomonas trioralisis the most abundant and widely distributed species in Ontario and is clearly eurytopic in its requirements for growth. It is common in a variety of lakes having Secchi disc visibilities of 2–10 m and pH and alkalinity ranges of 5.8–8.5 and 5–150 mg CaCO3/L, respectively.

ISSN:0008-4026    

DOI:10.1139/b81-018

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

A greenhouse experiment was conducted to examine the effects of water depth on the growth and reproduction ofScirpus maritimusL. Plants grown at or above the water surface had higher shoot survivorship, greater numbers of vegetative tillers, and higher underground biomass, while seed production was small. With increasing water depth plants had taller shoots and greater seed production but total biomass, numbers of vegetative tillers, and underground biomass were reduced. This shift from clonal growth to seed production with increasing water depth is interpreted as a strategy that permits survival ofS.maritimuspopulations through the wet and dry climatic periods of the Canadian prairies.

ISSN:0008-4026    

DOI:10.1139/b81-019

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The development of sori, sporogenesis, and characteristics of the hyphae inUstilago pustulataandU.scabiosaehave been investigated by light and scanning electron microscopy. The septa of both species form clamp connections. InU.scabiosaethe sporogenous cells are comparable with budding mycelia. The teliospores ofUstilago pustulataandU.scabiosaeare formed endogenously in chains.

ISSN:0008-4026    

DOI:10.1139/b81-020

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Bean plants, when inoculated withFusarium oxysporumdeveloped disease symptoms 7–9 days later and died within the next 3 weeks. The most common visible symptoms of the disease were wilting, yellowing, vein clearing, and necrosis of the leaves. Just before expression of these symptoms, from 5 days onwards, the leaves of the infected plant respired at a higher rate than those of the healthy plant. With the appearance of the foliar symptoms on the 7th or 8th day, however, the respiration rate began to fall steadily until the plant wilted completely. The tracheal sap of the inoculated plant was found to be toxic and increased the rate of respiration of leaf tissues.

ISSN:0008-4026    

DOI:10.1139/b81-021

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The nondestructive pulse method for studying14C-labelled photoassimilate translocation inAlaria esculentahas been adapted for species of Laminariales with flat, thick blades, in this case,Laminaria digitata. A 1-h pulse of [14C]bicarbonate(25 μCi) was applied to one side of the blade surface via a 12 mm diameter by 22 mm high, closed cylindrical incubation chamber. The upper 20-mm closed portion of the chamber was removed after the incubation period, the lower 2-mm open portion remained glued to the blade surface during the subsequent translocation period. A Geiger-Müller (G-M) detector probe with a 50 mm diameter end-window was used to measure the disappearance of radioactive organic matter from the pulsed region over the next 11–12 days. Accurate monitoring of the movement of14C-labelled solutes through the cortex and into the medulla was confounded by changing absorption of radioactivity by the cortex. Uniform absorption was achieved once the translocatable radioactivity reached the medullary conducting cells (sieve filaments). Thus arrival and accumulation of14C-labelled assimilate in the blade sink (meristem) was reliably measured with the G-M probe. ForLaminaria digitata, the translocation velocity of the moving solute front was 1.7 cm∙h−1. The specific mass transfer of carbon was estimated at 0.4 mg C∙week−1∙mm−2cross-sectioned medulla. Fifty-seven percent of assimilated carbon was exported in 10 days; 97% of the14C remaining in the source was in insoluble matter and 3% was in soluble matter. Cutting sieve filaments on the sink side of the incubation chamber did not stop short distance transport through the cortex, but significant14C-labelled photoassimilate was apparently unable to be re-routed around the cut as no radioactivity was detected in the sink area, the meristematic region at the base of the

ISSN:0008-4026    

DOI:10.1139/b81-022

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The ultrastructural cytology of the zoospores of the polycentric chytrids,Nowakowskiella elegans(Nowak.) Schroeter andCladochytrium replicatumKarling is very similar. In both there is a single lipid globule. A microbody lies between the lipid globule and a central, disc-shaped nucleus. On the other side of the nucleus there is a cluster of ribosomes. The ribosome cluster and nucleus are enveloped by a common double membrane. A number of mitochondria are appressed to the outside of the double membrane. A nonkinetosomal centriole is adjacent and parallel to the kinetosome, and there is an electron-opaque area at the base of the flagellum. Linked microtubules, numbering approximately 25 inN.elegansand 19 inC.replicatum, emerge from an area lateral to the kinetosome and run to the rumposome which lies on the surface of the lipid globule and faces the exterior of the zoospore. A number of the kinetosome-associated microtubules lie over the surface of the rumposome and appear connected to it. The significance of these results on taxonomic and phylogenetic concepts of the Chytridiales is discussed.

ISSN:0008-4026    

DOI:10.1139/b81-023

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Roots of 2-month-old Douglas-fir seedlings were exposed to six ethylene concentrations, ranging from 0.006 (soil ambient control) to 0.5 ppm, by adding ethephon, an ethylene-releasing compound, as a soil drench to the root zone. After 2 months exposure, 0.01–0.05 ppm had stimulated, 0.05–0.15 ppm had no effect, and concentrations > 0.15 ppm had inhibited lateral root formation. Root dry weight increased and shoot dry weight decreased as the ethylene concentration was increased.Ectomycorrhiza formation on 4-month-old seedlings inoculated withHebeloma crustuliniformewas not increased by exposure of the root zone to 0.1 ppm ethylene for 3 months, whether or not the seedling roots had been previously exposed to ethylene for 2 months before inoculation. By contrast, when 2-month-old seedlings preinoculated withFusarium oxysporumf. sp.piniwere exposed to 0.1 ppm ethylene for 2 months, disease incidence was significantly increased. These data suggest that the presence of ethylene in the root zone may have a different effect on root infections by pathogenic fungi than by mycorrhizal fungi.

ISSN:0008-4026    

DOI:10.1139/b81-024

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Nectar secretion in unpollinated flowers ofClintonia borealis(Ait) Raf. (Liliaceae) began as the tepals first opened, reached a maximum at about the time the anthers dehisced, and ceased after the tepals began to curl back. Total lifetime sugar production was highly correlated with flower size and was not affected by daily nectar removals. Nectar concentration varied widely as a response to fluctuations in atmospheric relative humidity. It is suggested that since freshly secretedClintonianectar ranged in concentration from 4 to 63% sugar by weight, comparisons of nectar concentration among different species may not be meaningful unless accompanied by environmental data at and prior to the time of sampling.

ISSN:0008-4026    

DOI:10.1139/b81-025

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Three races ofPuccinia graminis triticideveloped by successive mutations to give increased virulence (i.e., incompatible → mesothetic → compatible) on theSr6gene for resistance were compared histologically on cv. McMurachy (Sr6gene) growing at 20.5 °C. The length of the longest hyphae and the size of the lesions remained similar in the three interactions up to 3 days after inoculation and then comparative degrees of growth occurred in the following decreasing order; compatible > mesothetic > incompatible. Necrotic cells in the compatible interaction were infrequent (maximum of 6% of infection sites) and hyphae radiated out from the point of ingress in an unimpeded manner. Although necrosis in the incompatible interaction occurred 1 day in advance of necrosis in the mesothetic reaction, by the 6th day, 98–100% of the infection sites in both systems had necrotic cells. In the mesothetic reaction, hyphae grew beyond the area of necrosis in a high proportion (70% at day 6) of the infection sites whereas the incidence of such growth was much less (8% at day 6) in the incompatible reaction. The role of the hypersensitive reaction in these interactions is discussed.

ISSN:0008-4026    

DOI:10.1139/b81-026

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Five plots (15 m × 0.3 m) containing similar numbers ofVaccinium angustifoliumshoots were laid out within a clearing in a naturalPinus banksianastand. The area was burned in late April. Wooden screens were then erected to provide 0,25, 50,75, and 100% shade over the plots. Growth of blueberries and competing vegetation was monitored throughout the growing season using 10 quadrats (930 cm2) per plot. Soil characteristics, temperature, moisture, and light were measured.Quadrats with low preburn densities showed a greater increase in shoot numbers than those with high densities, regardless of shade. The times of shoot emergence and apical abortion were also independent of shade. Other blueberry characteristics were influenced by shade. Shoot density, shoot branching, and number of branches per shoot were highest in the open; frost damage was also greatest.However, blueberries under intermediate shade grew faster, had larger leaves, longer and stouter shoots, and experienced a more favorable water economy. In general, shade, considered detrimental to blueberries in the Atlantic Provinces, may be essential for optimal growth in Manitoba's continental climate.

ISSN:0008-4026    

DOI:10.1139/b81-027

出版商:NRC Research Press    

年代:1981

数据来源: NRC