摘要:

To use the15N natural abundance method to evaluate the symbiotic nitrogen fixation by actinorhizal trees, it is necessary to determine the isotopic identity of assimilated nitrogen from two sources: the soil and the air. This study reports an isotopic value of fixed nitrogen by two alder species (Alnus incana(L.) Moench andAlnus glutinosa(L.) Gaertn. growing on nitrogen-free medium in greenhouse experiments. The δ15N value of the aerial parts was −2. This value was stable with time and did not depend on theFrankiastrains used. This value could be used to estimate the nitrogen fixation in the natural ecosystem. Other parameters such as the mobilization of nitrogen reserves and the choice of the reference plant must be investigated to apply this method. The nodules of these two alder species were enriched in15N relative to the rest of the plant but there was no relationship between symbiotic effectiveness ofFrankiastrains and15N enrichment of nodules. On the other hand, for naturally growing trees, an enrichment in15N was found primarily in the vesicles of nodules that are the sites of nitrogen fixation.

ISSN:0008-4026    

DOI:10.1139/b88-177

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

The distribution of two systemic insecticides (carbofuran, dimethoate) in floral parts and nectar ofAjuga reptansL. (Lamiaceae),Brassica napusL. (Brassicaceae), andVicia fabaL. (Leguminosae), which differ in their types of nectary vascular supply, was determined. Radioactivity was detected in all floral organs when excised flowering plant tops were cultured in sucrose solution containing a combination of14C-labelled and formulated (unlabelled) insecticide. InA.reptansandB.napus, combined nectary tissue and nectar contained the most radioactivity on a fresh weight basis. Radioactivity was detected in floral nectar of all species, and in extrafloral nectar ofV.faba. Estimated concentrations of insecticide were much higher in extrafloral than in floral nectar ofV.faba; the presence of xylem in the nectary vasculature to the former may be responsible. However, the presence of xylem is not necessary for the secretion of systemic insecticides by nectaries.

ISSN:0008-4026    

DOI:10.1139/b88-178

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Bertia sinensissp.nov. is described and illustrated from Yunnan province, China. It is compared withB.moriformisvar.latispora. The taxonomic position ofBertiais reviewed.

ISSN:0008-4026    

DOI:10.1139/b88-179

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

At least 20 species of Trichomycetes (Zygomycotina) were dissected from the hindguts and peritrophic membranes of larval Diptera (Simuliidae, Chironomidae), Ephemeroptera, and Plecoptera in two high-altitude streams, and the trichomycete species diversity in the two streams was compared. Periodic sampling of larvae over a 6-week summer period showed that some gut fungi are widely distributed in their respective host types, whereas other fungal species are more localized. Insect populations had infestations that varied from low to as high as 100% of the insects dissected, depending on the fungal species. There was no general increase over time, from early to late season, in fungal species diversity or percentage of larval infestation, nor were larvae in second- and third-order sites of one stream generally more infested than in a first-order site in that stream.

ISSN:0008-4026    

DOI:10.1139/b88-180

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

A reexamination of the ascus structure, spore type, and chemistry of the saxicolous lichensPertusaria subplicansNyl. andP.rhodoleucaTh. Fr. has revealed them to be better classified within the genusOchrolechia. The following new combinations have therefore been introduced:Ochrolechia subplicans(Nyl.) comb.nov. andO. rhodoleuca(Th. Fr.) comb.nov.Ochrolechia rhodoleucais apparently restricted to northern Europe, leavingO.subplicansas the name of the American material. It is possible to discern two ecologically defined subspecies withinO.subplicans, each with slight chemical and morphological distinctions: subsp.subplicansand subsp.hultenii(Erichs.) Brodo comb.nov. A method is described for determining the precise location of gyrophoric, alectoronic, and variolaric acids within an ascoma by using a combination of conventional ultraviolet and spot-test techniques.

ISSN:0008-4026    

DOI:10.1139/b88-181

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Both phyllodes and so-called stipules develop on a whorl platform that surrounds the shoot apex. Phyllodes usually are initiated as radial primordia. During their development, although they become acrovergent and show a slight differentiation gradient from the abaxial towards the adaxial side, they retain a circular outline in transection until maturity. Longitudinally they differentiate into a basal pulvinus, a photosynthetic zone, and a terminal mucro. While only one concentric vascular bundle is formed in the pulvinus region, a cylindrical vascular network differentiates in the photosynthetic zone and only one collateral bundle surrounded by sclerenchyma develops in the mucro. In terms of both external symmetry and internal organization, phyllodes show a striking resemblance to stems, whereas so-called stipules appear more leaf-like because of their dorsiventral symmetry. After a detailed discussion of the role symmetry plays in various complementary interpretations of phyllodes and so-called stipules, symmetry transformations in angiosperms in general are illustrated. It is concluded that symmetry, growth pattern, and position do not constitute criteria that allow us to assign all known developmental pathways to mutually exclusive categories such as caulome or phyllome. Transformational analysis is suggested as a more adequate and dynamic tool for understanding the diversity of plant form.

ISSN:0008-4026    

DOI:10.1139/b88-182

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

In this second contribution to the Gasteromycetes of southern South America seven species ofVascellumSmarda found in that area are described. Of these,V. pampeanum(Speg.) Homrich is a new combination andV. cingulatumHomrich,V. cuzcoenseHomrich,V. delicatumHomrich, andV. hyalinumHomrich are new species. Complete descriptions and illustrations of all features of the species are given, together with a key for their identification.

ISSN:0008-4026    

DOI:10.1139/b88-183

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Cell elongation in the Ceramiaceae typically occurs by means of one or two bands located apically and (or) basally in each cell. In axial cells ofAntithamnion defectumtwo bands are present; however, most cell elongation occurs as a result of new wall deposition in bands at the base of each axial cell. In cells of determinate branches, only the basal band is present. In experimental conditions in which apical cells of indeterminate branches are differentially excised, location of the primary elongation band can be reestablished in relation to remaining indeterminate axes. Thus, the primary elongation band in axial cells is always basal with respect to indeterminate apical cells. When all indeterminate apices are removed, band growth becomes highly disrupted, and diffuse, irregularly located bands are formed. These results suggest that regulation of band position and elongation is through apical control.

ISSN:0008-4026    

DOI:10.1139/b88-184

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Monokaryotic strains ofTyphula incarnataLasch ex Fr. are able to produce small, unicellular, hyaline blastoconidia in basipetal sequence. The conidia are encapsulated by sticky mucilage and are derived from conidiogenous projections, each at the distal end of a conidiogenous cell. These structures elongate with formation of each new conidium. Tiny wall scars, visible in the transmission electron microscope, indicate an annellidic mode of conidiogenesis. However, the proliferation shows a weak sympodial tendency, owing to the partial plasticisation and integration of the preceding ring scars. This pattern was hitherto unknown for Basidiomycetes.

ISSN:0008-4026    

DOI:10.1139/b88-185

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

The conidia of monokaryotic strains ofTyphula incarnataLasch ex Fr. failed to germinate. However, homing reactions in compatible mycelia were induced. The homing branches of hyphae often fused with conidia. As a result of dikaryon formation the production of clamp connections took place. These characteristics, their “wet” surface, and their minute size permit us to term the conidia ofT.incarnata"spermatia."

ISSN:0008-4026    

DOI:10.1139/b88-186

出版商:NRC Research Press    

年代:1988

数据来源: NRC