摘要:

Physical and nutritional factors influencing the growth and sporulation ofConidiobolus obscurus(Hall et Dunn) Remaudière et Keller were studied using simple and fragmented factorial designs and centered composite designs. Culture conditions allowing maximum sporulation were a temperature of 20 °C, complete darkness, and a near neutral pH of around 6.5. Under our experimental conditions, dextrose influenced neither the growth nor the sporulation ofC.obscurus. The cations stimulating the formation of azygospores were magnesium and to a lesser extent zinc and manganese. Sulphur must be added to the medium in a reduced or oxydized form. Phosphates must be present in the culture medium, but at a concentration less than 30 mM/L. Vitamins stimulating sporulation were thiamine, biotin, and folic acid while pantothenic acid favoured growth. Among the 20 amino acids tested, proline, leucine, methionine, glutamic and aspartic acids, glutamine, asparagine, histidine, phenylalanine, lysine, and arginine were the most favourable for growth and sporulation ofC.obscurus. Growth and sporulation in the optimized defined medium containing 11 amino acids, four vitamins, four salts, and dextrose were comparable to the best results obtained in a nondefined medium composed of dextrose and yeast extract.

ISSN:0008-4026    

DOI:10.1139/b85-011

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

The interphase nucleus in secondary sporidia ofTilletia foetidaconsists of mostly diffuse chromatin, one or two nucleoli, and an area of heterochromatin located opposite an electron-dense, extranuclear spindle pole body (SPB). The interphase SPB is an oval- to bar-shaped, double-structured disc that has a crystallinelike substructure. During nuclear migration into nascent sporidia, SPBs and nucleoli are randomly oriented. At the onset of division, chromatin begins to condense and the SPB becomes located on a nuclear protuberance. Cytoplasmic microtubules terminate at the SPBs and multivesicular bodies surround the SPBs from the early stages of SPB division to early postdivision. SPB discs become spheroid and each develops a medial, dense layer. Then, a basal, dense layer develops and elongates as the SPBs separate and become positioned on opposite sides of the nuclear protuberance. The nuclear membrane opens opposite the SPB during SPB division. The nucleolus is extruded into a nuclear bleb and degenerates. SPBs migrate to opposing sides of the nucleus and become diffuse as a microtubular spindle develops between them. Some spindle microtubules terminate at dense chromatin patches that are contiguous with the major mass of chromatin surrounding the spindle. During late division stages, spindle microtubules often appear to be closely juxtaposed. Except for polar openings adjacent to the SPBs, the nuclear membrane is entire until late division when it degenerates in the midregion of the nucleus. During early postdivision, the SPB condenses into a small, dense sphere as the chromatin and heterochromatin opposite the SPB become diffuse. The SPB then elongates into a dense bar and SPB material increases, except at the midportion, reforming the double structure of interphase.

ISSN:0008-4026    

DOI:10.1139/b85-012

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

The period of initiation of sporopollenin precursors studied by transmission electron microscopy in the anthers of three species of the genusSaxifraga(S.cymbalariassp.huetiana,sempervivumandclusii) reveals two main phases. They are characterized successively by the elaboration of the ectexine (outer layer of the exine composed of sporopollenin) and endexine (inner layer of the same wall). This phenomenon has been observed in the tapetal periplasm and the sporal periplasm; the latter has been chosen as the reference point in establishing the chronology of the ontogenetic stages as well as the terminology of the sporopollenin structures. Proectexine and proendexine are distinctly stratified in the microspore while they become intermingled in the proorbicules. Proendexine could be elaborated according to a fluid mosaic model in relation to the plasmalemma. During this period, the relationships revealed between the plasmalemma–glycocalyx system (glycolemma) and the cytoskeleton (microtubules, microfilaments, and microfibrils) are emphasized. Thus, their functional role in the setting up of sporopollenin precursors is suggested.

ISSN:0008-4026    

DOI:10.1139/b85-013

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Some aspects of the population biology of two dune-forming perennial grasses,Ammophila breviligulataFern. andCalamovilfa longifolia(Hook) Scribn., growing along Lake Huron shoreline, were investigated under natural and controlled conditions. Plants ofA.breviligulataexhibit erratic flowering, ranging from no panicles in some areas to 16 per hundred tillers in others.Calamovilfa longifoliaplants occur as single clumps of varying diameters and flower profusely.Ammophila breviligulataexpands into adjacent areas by producing plagiotropic rhizomes ranging in length from 1 to several m and then producing ramets on some of the nodes. Such a growth form is best suited for rapid colonization of bare areas. Clumps ofC.longifoliaexpand outward in concentric circles through the development of diving rhizomes, and the radius of a clump increases by about 15 to 31 cm per year. This growth form is well suited for local occupancy.Ammophila breviligulatais more tolerant of burial (100 cm) in sand thanC.longifolia(60 cm).Calamovilfa longifoliaproduces larger number of caryopses per square metre thanA.breviligulata. The weight per caryopsis of both species is similar, but the significantly greater surface area per fruit ofA.breviligulataimproves its flotation ability in water, thus facilitating long-distance dispersal of fruits. Establishment ofC.longifoliaplants under natural conditions occurred almost exclusively from seedlings. In contrast, the establishment ofA.breviligulataseedlings was rare and almost all new plants along the beach originated from clonal fragments cast on the drift line by high waves.

ISSN:0008-4026    

DOI:10.1139/b85-014

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Studies on spatial pattern and seed dispersal ofLithospermum caroliniense(Walt.) MacMill. on Lake Huron sand dunes revealed that the ratio of pin to thrum plants was approximately 1: 1 on the south slope of the first dune ridge and slack. However, thrum plants had a higher proportion than pin plants on the crest of the dune ridge. The density of plants was highest on the south slope as compared with the other topographical zones. The spatial pattern of plants was nonrandom and plants were clustered in each of the three topographical zones. Most dispersed seeds ofL.carolinienseremained within 1 m of the parent plant. The seed dispersal was not radially symmetrical around the parent plant. The steepness of the dune slope affected the dispersal distance of some propagules. Some seeds were retained on the parent, but few of these seeds were normal. About 40 to 64% of the recovered seeds contained holes in the seed coat. Eight months after marking, about one-third of the original marked seeds were still intact.

ISSN:0008-4026    

DOI:10.1139/b85-015

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Pyrola sikkimensisis recognized as being of hybrid origin betweenP.minorandP.rotundifolia s.l. on the basis of several distinctive floral features that characterize hybrids ofPyrolain which one of the parents isP.minor. The similarity in morphology ofP.sikkimensistoP.media, an amphidiploid betweenP.minorandP.rotundifolia, suggests thatP.sikkimensisis conspecific withP.media.

ISSN:0008-4026    

DOI:10.1139/b85-016

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

The rootlet systems, kinetosomes, and transition zones in zoospores ofPhytophthora parasitica,Thraustochytrium aureum, andRhizidiomyces apophysatusand secondary zoospores ofSaprolegnia diclinaare compared. Rootlet systems inP.parasiticaandS.diclinaare very similar and there are only minor differences between these taxa in morphology of their transition zones. InP.parasiticaandT.aureuma number of differences exist in the rootlet systems, but the position and orientation of individual rootlets are similar. There are also differences between these taxa in the alignment of their kinetosomes, the morphology of their kinetosome cores, and transition zones.Rhizidiomyces apophysatushas rootlets that correspond in position and orientation toP.parasitica, but there are not as many rootlets and these are morphologically distinctive. However,R.apophysatusandS.diclinahave flagellar transition zones that are morphologically alike. Thus, probably the Hyphochytriomycetes are phylogenetically quite closely related to the Saprolegniales and more distantly related to the Peronosporales. In contrast, the Thraustochytriales are distantly related to the Oomycetes and Hyphochytriomycetes, but nonetheless similarities in the flagellar apparatus indicate that all have a common ancestor.

ISSN:0008-4026    

DOI:10.1139/b85-017

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Cell proliferation inAllium sativumL. primary root meristems is stimulated by poly-D-lysine. This effect has been studied on asynchronous and on hydroxyurea-synchronized meristems using cell kinetics techniques and DNA microdensitometry. The rapid increase of mitotic indices is the result of the onset of mitosis in 4C cells which are arrested in G2. However, neither the initiation of DNA synthesis in G1cells, nor the labelling index of roots continuously incubated with tritiated thymidine, are altered. Thus, poly-D-lysine has a selective effect on G2cells, triggering the onset of mitosis in those cells. Our results, which show that mitosis can be induced in G2cells by an exogenous supply of a polycationic compound, are discussed in relation to the occurrence and the features of G2-arrested cells within root meristems.

ISSN:0008-4026    

DOI:10.1139/b85-018

出版商:NRC Research Press    

年代:1985

数据来源: NRC