摘要:

The inoculation of the host plantComptonia peregrina(L.) Coult. (Myrica asplenifoliaL.) by a pure culture of a free-living actinomycete, isolated fromComptoniaroot nodules by Callahamet al. (1978, Science, 199: 899–902), was successful. Short-term and long-term nodulation tests confirmed the infectivity of theComptoniaisolate. Acetylene reduction assays of the nodules induced by this prokaryote isolate demonstrated nitrogen fixation activity. This nitrogen fixation activity was able to sustain a prolific growth of the nodulated host plants growing in a N-free substrate. Indirect immufluorescence reactions, using specific gamma globulin against the actinomycetal isolate of theComptoniaroot nodule, demonstrated the identity of this actinomycete in thesein vitroproducedComptoniaroot nodules. Ultrastructure of theComptoniaisolate, developing as a free-living or endophytic actinomycete, was observed by light microscopy, freeze etching, and transmission electron microscopy. The free-living filamentous and sporulating isolate produced typical hyphae and vesicles when growing as an endophyte in theComptonianodule. These endophytic hyphae and vesicles were always encapsulated by a polysaccharide material which was surrounded by a host membrane envelope. A polysaccharide capsule was not demonstrated on the free-livingComptoniaisolate. The endophytic vesicles were club shaped and highly septate. Such vesicles were never produced by the free-living isolate growing in an artificial medium. TheComptoniaisolate is a spore former in pure culture and was able to sporulate in basal tissues of 5-month-oldComptonianodules.

ISSN:0008-4026    

DOI:10.1139/b78-316

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Nitrogen fixation was measured using the acetylene reduction technique in soil cores of 13 nonnodulated, herbaceous plant species growing in mesic and wetland habitats. Six species that grew in a well-drained portion of an old field exhibited low rates of N2fixation (7 g N∙ha−1∙day−1). A bulrush,Scirpus atrovirens, which grew in an area of compacted soil in the old field, showed a moderate rate of N2fixation (30–100 g N∙ha−1∙day−1). These old field species exhibited a lag of only a few hours before a constant rate of acetylene reduction occurred. The estimated rates for the six wetland species were generally higher, and there was a lag such that the activity was still increasing after 20 h of incubation. N2fixation in cores ofS. atrovirenswas primarily associated with the roots and adhering soil. Incubation of the cores in N2for 24 h caused a fourfold increase in the acetylene reduction rate over that in air, although the rates during the first 4 h were

ISSN:0008-4026    

DOI:10.1139/b78-317

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Axenic cultures of the fusiform rust fungus (Cronartium fusiforme) were initiated from basidiospores, aeciospores, and uredospores. The morphology, cytology, and nuclear condition of the mycelium from the three spore stages are described and illustrated. Cultures derived from aeciospores and uredospores ofC. fusiformeare reported for the first time. An improved culture medium is described. Inoculation of slash pine (Pinus elliottiivar.elliottii) seedlings with suspensions of mycelium from basidiospores induced some typical galls which produced pycnial exudates and aeciospores. On synthetic medium, cultures from basidiospores were monokaryotic. Mostly dikaryotic mycelium was produced from aeciospores and uredospores, but some monokaryotic hyphae were observed.

ISSN:0008-4026    

DOI:10.1139/b78-318

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The authors have described the morphological deformations owing to copper deficiency inPseudotsuga menziesiiandPicea sitchensis. The experimental studies entered upon have enabled us to determine the copper deficiency level for both species. With Douglas fir, the deficiencies occur under 4 ppm in the leaves; with spruce, the level is set at 2.5 ppm. Treatment of the plantations with 20 g of copper sulphate per tree increases the copper content in the leaves. This treatment also brings about the straightening of the distorted axes; the recorded effects depend upon the state of the saplings before treatment.

ISSN:0008-4026    

DOI:10.1139/b78-319

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Cultured cell lines ofHaplopappus gracilisresistant to the purine analog 8-azaguanine (AG) have been isolated. One such line is 50 times more resistant to the drug than are wild-type cells. This line of AG-resistant cells also exhibits increased resistance to 8-azaadenine, but it responds to kinetin in a manner identical with that of wild-type cells. The resistance phenotype is stable for many generations in the absence of selection. In cultures of wild-type or mutant cells, more than 95% of cells are diploid.

ISSN:0008-4026    

DOI:10.1139/b78-320

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Seven years (1970–1977) of comparative light and electron microscope studies show that extensive cell wall disruption and breakdown occur consistently in elm xylem tissues infected byCeratocystis ulmi(Buism.) C. Moreau. These alterations, noticeable even in incipient infection, can be related to the severity of wilting development and occur in association with the presence of an unbound osmiophilic material containing fine fibrillar material, dense particles of approximately 15 nm, and multilamellate structures. Masses of unbound osmiophilic material in host walls and walled fungal cells with which it is sometimes continuous are highly and exclusively labeled following injection of [6-3H]thymidine.The presence of osmiophilic material in host walls and the interrelation between the two was further established by examining stereoscopic pairs of prints taken at various angles with a goniometer. This type of cell wall breakdown seems difficult to relate to other known types of wood rots. Further discussion on the possible nature and origin of the osmiophilic material is presented.

ISSN:0008-4026    

DOI:10.1139/b78-321

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Light and electron microscopy have revealed that the meiotic-1 (mei-1) mutant ofNeurospora crassais defective in chromosome pairing (asynaptic) although plenty of axial components of the synaptonemal complex are produced and occasional tripartite synaptonemal complexes can be formed. Themei-1mutant is most probably defective in bringing the homologous chromosomes together for pairing and for assembly of the synaptonemal complex. Themei-1mutant is also defective in nuclear separation which leads to a four-poled spindle at the subsequent division. The lack of chromosome pairing, the incomplete assembly of the synaptonemal complex, and the four-poled spindles account for absence of recombination and for the nondisjunction found in genetic analysis.

ISSN:0008-4026    

DOI:10.1139/b78-322

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Stipe elongation rates were measured over an 18-month period which included one normal summer and one in which there was unusually heavy epiphytism and defoliation. Calculated standard growth rates (G) followed atypical boreal pattern, rising in February through April, with a summer maximum of ca. 40 mm/day, and falling in October and November. This contrasts withM. pyriferain southern California, which hasGca. 70 mm/day throughout the year. The maximum number of fronds that could be produced in the growing season by a frond series of M.integrifoliais about 20, but the number actually produced is 8; many frond initials are lost through grazing or abrasion or may be suppressed by high frond densities.

ISSN:0008-4026    

DOI:10.1139/b78-323

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The grassAgropyron tsukushiensevar.transiensis native to Far East Asia, andHordeum compressumis native to southern South America. They were found to be susceptible to all the races that they were tested to of the following: loose smut of wheat (Ustilago tritici): loose, covered, and false loose smut of barley (U. nuda, U. hordei, andU. nigra); loose and covered smut of oats (U. avenaeandU. kolleri); and head smut of grasses (U. bullata). The two grasses are the first known common hosts for these smuts and will be used to study the relationships between these pathogens.

ISSN:0008-4026    

DOI:10.1139/b78-324

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Differentiation in a stem-derived callus ofRuta graveolenswas studied by correlated light and electron microscopy. Shoot apical meristems, some of which initiated leaves, differentiated randomly at the surface of the callus. Some of the apical meristems had a tunica–corpus organization. Cells of the tunica and corpus had large nuclei with prominent nucleoli, small vacuoles, mitochondria, endoplasmic reticulum cisternae, and leucoplasts. The leaves were radial and had well developed stomata and chloroplasts of two types, one storing large starch grains and the other with no starch but with well developed grana. Lysigenous and schizolysigenous secretory glands were initiated in the leaves and towards the periphery of the callus. Central cells in the lysigenous glands underwent lysis forming a gland lumen into which lipid-like material from the degenerating cells was released. During early stages of cell lysis, breakdown of the middle lamella occurred, followed by the degeneration of cell walls. The lipid-like deposits are thought to be the essential oils known to be produced by these callus cultures. Schizolysigenous glands are formed by the separation of gland cells along the middle lamella and the subsequent development of an epithelial layer or layers surrounding a gland lumen. The cytology of epithelial cells was characterized by numerous ribosomes and the presence of plastids with lipid-like deposits, rough endoplasmic reticulum which occurred either as sheets of cisternae or tubular profiles, and osmiophilic deposits in the cytoplasm. Changes in the epithelial cell walls bordering on the gland lumen indicated that these cells were probably undergoing lysis in older stages of gland development.

ISSN:0008-4026    

DOI:10.1139/b78-325

出版商:NRC Research Press    

年代:1978

数据来源: NRC