摘要:

The nature of the fungus–alga association between the lichen-forming basidiomyceteDictyonema irpicinumMont. and itsScytonemahost was investigated using light and electron microscopical techniques. The lichen-like basidiocarp is established as a result of the active capture of free-livingScytonemasp. trichomes by the fungal symbiont. A septate, intracellular haustorial hypha is produced by the basidiomycetous fungus within the filamentous blue-green alga. This specialized haustorial apparatus appears to enhance the survivorship of the otherwise ephemeral fungus, allowing it to maintain a long-term, stable association with the algal host.

ISSN:0008-4026    

DOI:10.1139/b80-124

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Levels of gibberellins and cytokinins in dormantAvena fatuaL. seeds were measured by bioassay during the afterripening process. Little change in the level of either hormone was detected in the dry seed. Following imbibition of fully afterripened seed, however, gibberellin levels increased while cytokinin levels declined. Seed strains varying in their degree of dormancy were also analysed for hormone levels; a significantly higher level of cytokinin activity was found in the most dormant strain compared with the least dormant strain. Low levels of bound hormones, including cytokinin ribotides and gibberellin glucose conjugates, were detected following enzyme hydrolysis but neither class of compounds varied greatly in level during afterripening.The major cytokinins detected inAvena fatuaseeds cochromatographed with zeatin-9-glucoside, zeatin riboside, and zeatin on both HPLC columns and chromatography paper. The major gibberellin activity cochromatographed with GA4/GA7on silica gel partition columns and thin-layer plates.Germination studies demonstrated that GA4/7is significantly more active than GA3in promoting the germination of dormantAvena fatuaseeds. External applications of cytokinins were not found to affect the germination of dormant seed, but did promote germination in partially afterripened material.

ISSN:0008-4026    

DOI:10.1139/b80-125

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Isolates of five species of aquatic hyphomycetes were grown in pure culture with hickory leaf material as the sole source of carbon and energy. Enzymatic activity by all five species resulted in the skeletonization of leaves through maceration of the leaf matrix and subsequent release of leaf cells as fine particulate organic matter. Fractionation and analysis of leaf material after incubation indicated that all five species metabolized (degraded) cellulose and two species metabolized (degraded) hemicelluloses. In cultures inoculated withTetracladium marchalianum, fine particulate release coincided with increases in fungal biomass (ATP) and activity of enzymes in the supernatant which degraded carboxymethylcellulose, xylan, and polygalacturonic acid. Macerating activity increased with increasing pH suggesting involvement of pectintrans-eliminase in the softening of leaf tissue by this fungus.

ISSN:0008-4026    

DOI:10.1139/b80-126

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The fusion of protoplasts isolated from leaves ofCatharanthus roseusandNicotiana glaucawith protoplasts fromHaplopappus graciliscell cultures resulted in heavy precipitation of granules in vacuoles of the fusion products. The occurrence of this precipitate is seen as an indication that subsequent to protoplast fusion cell sap vacuoles fuse also.

ISSN:0008-4026    

DOI:10.1139/b80-127

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Harpella leptosa(Harpellales, Harpellaceae) from the midget region of blackfly larvae (Simuliidae) is described. With the light microscope it is distinguished from the only known species of the genus,H. melusinae, primarily by its smaller dimensions and less conspicuous holdfast, but electron microscopic studies reveal significant differences in the substructure of the trichospore appendages and holdfast apparatus.Harpella leptosais presently known only from the northern Rocky Mountains. The two species ofHarpellaare sympatric, and occasionally live simultaneously in the same host gut.

ISSN:0008-4026    

DOI:10.1139/b80-128

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The four lodicules of the male spikelet ofZea maysL. are supplied by one, two, or three traces. In the lower regions of the traces intermediary cells and a few phloem transfer cells occur with the companion cells and sieve tubes. Xylem transfer cells with a variety of wall thickenings intermingle in the lower regions of the traces with tracheary elements. Tracheary elements and sieve tubes in this region do not touch but are separated by the phloem and xylem parenchyma. As the lodicule trace nears the base of the lodicule, intermediary cells and transfer cells diminish. A bundle sheath surrounds the lodicule trace but does not surround the minor veins of the lodicule proper. Within the lodicule proper the trace branches prolifically, and the minor veins become peripherally placed. Most of the minor veins contain vessels and sieve tubes but a few contain sieve tubes alone. Companion cells occur in some veins but not in others. Vessels and sieve tubes frequently touch each other. Many minor veins end simultaneously in sieve elements and tracheary elements but some end in one or the other cell type. Parenchyma cells with wrinkled walls occur near the minor veins. The abaxial epidermis of the upper regions of the lodicule contains stomates.

ISSN:0008-4026    

DOI:10.1139/b80-129

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Tylosis formation in American elm was sparse during development ofCeratocystis ulmiinfection in the period of highest tree susceptibility, as observed in numerous periodically sampled field-inoculated trees from 1970–1978. Tyloses are more frequent in greenhouse-grown than in field-grown trees. They are abundant, sometimes in invaded vessels, in field samples collected after acute wilting (in surviving trees) at the end of summer or during the following spring. Aborted, collapsed, or disintegrated tyloses have been observed. The first tylosis wall layer (continuous with the protective layer of the parenchyma cell) is thickened in some tyloses; papilla-like structures are present in others. Often, masses of osmiophilic material are located outside the tylosis, with strands extending into the tylosis wall. An almost translucent, often lamellate layer is deposited in more mature tyloses.Other structures having the external configuration of tyloses but differing from them in organization, form abundantly in vessels shortly after inoculation in both greenhouse- and field-grown trees. Called bubbles, these structures are similar to, and often in continuity with, a coating on inner vessel walls.These observations are discussed in relation to previous ultrastructural observations of infected elms and in general with other plant wilts of fungal origin.

ISSN:0008-4026    

DOI:10.1139/b80-130

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

An electron microscope study reveals considerable variation in the holdfast structure by which the fungal thalli of Trichomycetes attach to the gut lining of their arthropod hosts.Enterobryus attenuatus(Eccrinaceae) has a compound holdfast system where the holdfast substance is secreted through a reticulate ring complex located at the base of each individual thallus. The ring complex is rich in polysaccharides, as is the outermost layer of the cell wall.Enterobryus elegansproduces large, single holdfasts with a fibrous matrix containing numerous parallel channels, some of which open to the gut lumen.Genistellospora homothallica(Legeriomycetaceae) has a dense and homogeneous biconcave holdfast, whereasPennella angustispora, belonging to the same family and found in the same host, secretes an amorphous cementing substance throughout the length of the basal cell wall.

ISSN:0008-4026    

DOI:10.1139/b80-131

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Nitrate reductase activity, the assimilation of NO3−, and growth were studied in suspension cultures ofRosacv. Paul's Scarlet grown in media with either 24 mM NO3−,or with 24 mM NO3− + 0.91 mM NH4+.Ammonium partially repressed the development of nitrate reductase during the first 4 days of growth and the degree of repression was more pronounced when cells were provided with lower concentrations of NO3−. The repression of nitrate reductase by NH4+was only observed when casein was used during enzyme extraction. The repression of nitrate reductase activity by NH4+was not recognized in earlier work when no casein was used.The presence of casein in the extraction or assay medium increased the total recoverable nitrate reductase activity. The enhancement was differential depending on cell age with the greatest influence being on young and old cells where 100 and 400% enhancements were observed, respectively.In vitronitrate reductase activity correlated well with NO3−assimilation. Over 14 days of growth, the ratio of total nitrate reductase activity to the total amount of NO3−reduced was 3.8 for cultures grown with or without NH4+. Cultures grown with NH4+achieved 80% more fresh weight and reduced 70% more NO3−over 14 days than cultures grown without NH4+.

ISSN:0008-4026    

DOI:10.1139/b80-132

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The population ecology of the annual plantCakile edentulawas studied on a gravel bar in Halifax County, Nova Scotia, where it grows in a two phase mosaic consisting of (1) open shingle or gravel and (2) thick mats of deadZostera marinawrack. Cohorts of seedlings were marked and regularly counted in both habitats. Reproductive output and seed dispersal were also studied.There were marked differences inC. edentulaecology between the two habitats. In general, survivorship and reproductive output were both greater in shingle. However, caterpillar grazing in late summer was concentrated on shingle plants, with the eventual result that net reproductive output was greater in wrack. There was no evidence of seed movement between wrack and shingle.Seedlings ofC. edentulaoften grew in dense clusters around the remains of the previous year's parent(s). In both habitats,C. edentulaseedling density declined with distance from the centre of clusters. Reproductive output increased with distance in both habitats; survivorship increased with distance only in wrack. Distal fruit segments were dispersed further than proximal segments; thus seedlings derived from distal segments tended to grow further from the previous year's parent, and in turn had higher survivorship and reproductive output. Distal fruit segments are normally thought to function primarily for long-distance dispersal; on shingle beaches "long-distance dispersal" of less than a metre could significantly improve the reproductive success of a seedling.

ISSN:0008-4026    

DOI:10.1139/b80-133

出版商:NRC Research Press    

年代:1980

数据来源: NRC