摘要:

Striga hermonthica(Del.) Benth., (Scrophulariaceae) a parasite of pearl millet (Pennisetum typhoides(Burm.) Stapf and Hubb.), is attached to its host roots by suckers (also called haustoria). The anatomy and ultrastructure of the haustoria described in this study, including the cytology of such haustorial features as intrusive cells, intertracheidal parenchymatous cells, axial vascular core, hyalin tissue, and radial vascular system. Investigations with both electron and fluorescence microscopy did not disclose the presence of phloem. This lack is considered to be a common feature of the haustoria of parasitic Scrophulariaceae.

ISSN:0008-4026    

DOI:10.1139/b88-289

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Observations concerning morphology, structure, and ontogeny of the thallus of a squamulous species,Endocarpon pusillumHedw., are presented. The latter is composed of squamules, most of which are interconnected by a well developed network of rhizomorphs. Four types of squamules have been distinguished according to their morphological characters and their location with regard to rhizomorphs. The squamules ofE.pusillumare characterized by the lack of lacunae and the presence of numerous rhizomorphic-like hyphae in the medulla, which are in topographical relation with the hyphae of the rhizomorphs. Morphological and structural data allowed us to follow an ontogenic continuum from the smallest squamules, i.e. the least differentiated, to the one bearing fruiting-bodies, which show numerous rhizomorphs.

ISSN:0008-4026    

DOI:10.1139/b88-290

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Sydowia semenosporasp.nov. (anamorph:Sclerophoma semenosporaFunk) is described from amabilis fir (Abies amabilis(Dougl.) Forbes) on Vancouver Island, B.C., Canada.

ISSN:0008-4026    

DOI:10.1139/b88-291

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Two new species,Lepanthes apricaandLepanthes oreophila, are described from the state of Oaxaca, Mexico. The latter species is similar toL.blepharistesRchb.f. andL.schiediiRchb.f.Lepanthes apricadoes not closely resemble any other Mesoamerican species.

ISSN:0008-4026    

DOI:10.1139/b88-292

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

The holotypes ofXanthoconium affine,X.affinevar.maculosum,X.purpureum,X.stramineum, andGyroporus woodiaewere studied microscopically. The results supported earlier type studies ofX.affineandX.affinevar.maculosumby other authors and confirmed the synonymy ofG.woodiaeandX.stramineum.

ISSN:0008-4026    

DOI:10.1139/b88-293

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

The role of ethylene in mediating the response of primary roots ofZea mayscv. Merit to experimentally imposed mechanical impedance was examined. Root elongation was stimulated during the first 100 min of impedance. Within 300 min, impedance inhibited ethylene evolution while simultaneously stimulating 1-aminocyclopropane-1-carboxylic acid production. The root cap is not necessary for the observed impedance-mediated inhibition in ethylene, and ethylene evolution was not stimulated by excising root caps. Ethylene synthesis in roots is normally controlled by the production of 1-aminocyclopropane-1-carboxylic acid.

ISSN:0008-4026    

DOI:10.1139/b88-294

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

A new anamorph genus,Zetesimomyces, is proposed to accommodate a coelomycetous anamorph collected on leaf litter in Cuba and New Zealand.

ISSN:0008-4026    

DOI:10.1139/b88-295

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

A dark lignicolous hyphomycete with dichotomously branched conidiophores ending in clustered lobes giving rise to catenate, septate conidia is described and illustrated asDicholobodigitus nigergen. et sp. nov.

ISSN:0008-4026    

DOI:10.1139/b88-296

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Sixty-three upland True and Upper Coastal Prairie grasslands were sampled for vegetation composition and soil variables. The first axis from principal components analysis produced a south to north arrangement of stands along which temperature and precipitation decrease and soil organic matter increases (P < 0.0001). The second principal components analysis axis was related to a soils gradient, primarily within Texas communities, which had more varied soils than grasslands to the north. Species response curves against the first axis showed a continual replacement from north to south, withSchizachyrium scopariumandPaspalum plicatulumdominants in the south,Andropogon gerardiimore important in central and northern communities, andStipa sparteaandSporobolus heterolepisimportant in the north. The C3/C4ratio of grasses increased rapidly northward from Nebraska. Species diversity and richness did not vary greatly and showed nonsignificant correlations with environmental variables across this latitudinal gradient. Stand relationships from cluster analysis corresponded with the results of principal components analysis, and based on these analyses, plus a review of the literature, seven community types were recognized. Five form a continuum, across whichAndropogon gerardiiincreases northward andSchizachyrium scopariumincreases southward, while two are limited to high-precipitation areas of north Texas.

ISSN:0008-4026    

DOI:10.1139/b88-297

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

The present investigation deals with the production of extracellular and intracellular endoglucanase and β-glucosidase enzymes and the study of their multiple molecular forms inChaetomium erraticum. WhenC.erraticumwas grown on carboxymethyl cellulose as the sole carbon source, more than 90% of the endoglucanase was extracellular, while most of the β-glucosidase was intracellular. However, the relative distribution of these enzymes varied with the age of the culture. Two forms of each of endoglucanase (EG-I, EG-II) and β-glucosidase (βGlu-I, βGlu-II) were detected after 4 and 6 days of incubation, respectively. Additional intracellular forms of endoglucanase and β-glucosidase i.e., EG-III and βGlu-III, appeared at later stages, when perithecia developed, indicating that EG-III and βGlu-III are related to the development of perithecia. These multiple molecular forms were further differentiated by their response to temperature, pH, ethylenediaminetetraacetic acid, and metal ions.

ISSN:0008-4026    

DOI:10.1139/b88-298

出版商:NRC Research Press    

年代:1988

数据来源: NRC