摘要:

One of the causal agents of fisheye rot of apples in cold storage, long known under the inapplicable name ofCorticium centrifugumsensu Butler, is redescribed asButlerelfia eustaceiWeres, & Illman, gen. et sp. nov., named in honour of H. J. Eustace and L. F. Butler, who first made it known to science.

ISSN:0008-4026    

DOI:10.1139/b80-016

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The leaf morphology and anatomy, fruit morphology, growth forms, and distribution patterns of species of the three goldenaster generaChrysopsis, Heterotheca, andPityopsiswere analyzed and compared, with the conclusion that they should be treated as three distinct genera. The species ofChrysopsiswere characterized by flexible flagelliform hairs.Heterothecahad stiff uniseriate, osteolate hairs.Pityopsishad long filamentous hairs that adhered to each other in a reticulate pattern.ChrysopsisandHeterothecahad similar leaf anatomy and compressed-obconic fruits (except for the epappose ray floret fruits of sect.Heterotheca).Pityopsishad distinctive leaf anatomy and morphology and had fusiform fruits.Chrysopsisincluded one annual plus biennial to weakly perennial and true perennial species distributed primarily in Florida.Pityopsisincluded only herbaceous perennials with fibrous roots distributed throughout the southeastern United States for the most part.Heterothecaincluded mostly herbaceous perennials with taproots distributed throughout western North America from Canada to Mexico. Some members of sect.Heterothecawere annuals occurring in the southern United States. A key to the genera and sections of the goldenasters has been included. The following new nomenclatural combinations have been made:Chrysopsis gossypinassp.cruiseana, C. gossypinassp.hyssopifolia, C. gossypina,f.trichophylla, Heterotheca camphorata, Pityopsis adenolepsis, andPityopsis graminifoliavar.microcephala.

ISSN:0008-4026    

DOI:10.1139/b80-017

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The karyotypes of all species ofChrysopsiswere analysed and four basic complements were recognised. TheX = 5 karyotype was possessed by all sevenn = 5 species and consisted of three submetacentric and two acrocentric chromosomes, one bearing the nucleolar organizer region medially on its short arm. EachX = 4 species had a distinct karyotype. Then = 4 karyotype ofC. marianahad diverged less from theX = 5 karyotype than that ofC. pilosa. The X2 = 9 karyotype shared by threen = 9 taxa was found to be little more than a combination of theX = 5 karyotype and theX = 4marianakaryotype and was therefore of allopolyploid origin. Some shifting in the location of the nucleolar organizer region has occurred in each group.

ISSN:0008-4026    

DOI:10.1139/b80-018

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Mitotic karyotypes and meiotic pairing were studied in wild, cultivated, and experimentally produced hybrids betweenChrysopsis godfreyi(n = 5) andC. gossypinassp.cruiseana(n = 9) and betweenC. godfreyiandC. linearifolia(n = 5). Hybrids were first detected on morphological grounds. During metaphase 1 in the amphidiploid2n = 14 hybrids (godfreyi×cruiseana) the following associations were most frequent: 3III + 2II + 1I, 2III + 3II + 2I. During meiosis in the 2n = 10 hybrid (godfreyi×linearifolia) an association of 4II + 2Iwas most frequently observed. Meiotic and karyotype data indicate that ann = 5 taxon gave rise to ann = 4 taxon; these or their derivatives hybridized to yield ultimately a 2n = 18 allopolyploid taxon. Some changes in gene arrangement have occurred in then = 9 taxa and in onen = 5 phylogenetic line, as indicated by chromosome and chromatid bridge formation in meiosis of the hybrids.

ISSN:0008-4026    

DOI:10.1139/b80-019

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The main morphological and cytological changes which accompany oospore maturation and germination in an emasculate isolate ofSaprolegnia feraxhave been followed by light and transmission electron microscopy. Oospore development proved similar to that described in antheridiate species except for the absence of motile granules within the central ooplast vacuole. Germination followed within a few days of maturation although it did not occur synchronously within a single oogonium. The ending of dormancy is indicated by a thinning of the oospore wall and a decrease in cytoplasmic refractivity. A new germination wall is secreted around the protoplast and the contents of the central ooplast break down and are partially dispersed into the peripheral cytoplasm as it becomes transformed into a typical somatic vacuole. Oospores swell slightly before the emergence of between one and four germ tubes. These often grow extensively within the oogonium, occasionally infesting and possibly parasitizing neighbouring germlings, before rupturing either the thin-walled pits or basal septa. After emergence most germ tubes continue to grow vegetatively in a sparsely branched fashion, although a few develop terminal sporangia. Oospore germination in this isolate is compared with that described in other oomycete species.

ISSN:0008-4026    

DOI:10.1139/b80-020

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The fine structure of oogonium and oospore walls ofSaprolegnia feraxand the changes associated with germination are described. Mature oogonium walls have well defined primary and secondary layers with pits arising as the result of the localized absence of secondary wall deposition. The mature oospore wall has a 0.1 μm thick outer wall separated from a 2.0 μm thick inner wall by a thin (40 nm) electron-dense, multilaminate layer. Within the inner wall is an optically dense (0.5 μm) inner zone composed of particulate and membranous material. At the onset of germination most of the microfibrillar inner wall is digested and reabsorbed and a new germination wall is secreted around the protoplast. As the spores swell the vestigial oospore remnants either rupture or disintegrate and germ tubes develop by the outgrowth of the germination wall. Elaborate plasmalemmasome complexes appear during the period of spore swelling and the mature germling walls become thickened and contain abundant lomasomes and peglike ingrowths. Oospore wall morphogenesis inSaprolegniais compared with that in other oomycetes and discussed in relation to the possible mechanisms of dormancy.

ISSN:0008-4026    

DOI:10.1139/b80-021

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Changes in the structure of the main cytoplasmic organelles (excluding wall and nuclei) during the formation, maturation, and germination ofSaprolegnia feraxoospores have been followed by transmission electron microscopy and their status assessed by stereologic analysis of micrographs. During oosphere differentiation there is a steady accumulation of lipid and dense-body (lipo-phospho glucan complexes) reserves; at the same time the overall status quo of other organelles is maintained. Oospore maturation is associated with the coalescence of dense-body vesicles, partial utilization of neutral lipid reserves, and dramatic decline in most other cell organelles. This is preceded by a marked increase in lipid-associated microbodies (glyoxysomes) which appear to develop from the fragmentation of cisternae of smooth endoplasmic reticulum. At the onset of germination the inner oospore wall is rapidly digested and normal levels of cytoplasmic organelles is restored. The neutral lipid fraction progressively declines with half the reserves being utilized before germ tube emergence. The osmiophilic dense-body vesicle derived ooplast matrix disintegrates and dense-bodylike granules are released into the expanding central vacuole and peripheral cytoplasmic vesicles, which eventually become associated with cup-shaped mitochondria. Unusual reticular bodies (mitochondria), crystalline aggregates (virus particles), and multivesicular bodies are also described in the cytoplasm of germinating spores. The results are discussed in relation to the possible metabolic pathways associated with the utilization of endogenous reserves.

ISSN:0008-4026    

DOI:10.1139/b80-022

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Changes in nuclear ultrastructure during the formation, maturation, and germination of oospores produced by an agamospermous (emasculate) isolate ofSaprolegnia feraxare described. Oogonium nuclei undergo synchronous meiotic divisions which appear identical to those previously reported in antheridiate species. Fusion of two typical gametic nuclei result in the formation of a single, unusually large, restitution nucleus within delimited oospheres. During the activation phase of germination the nuclei undergo three or four successive, near synchronous, mitotic divisions which appear similar to those described in other oomycetes. There was no evidence to support the occurrence of zygotic meiosis. Some nuclei in germinating oospores contain unusual spheroidal and lamellar inclusions, whereas others have abnormally large, irregularly lobed, profiles. Nuclear autolysis was also a common event in germlings. These results are compared with those in other oomycetes and the evidence supporting automictic sexuality discussed.

ISSN:0008-4026    

DOI:10.1139/b80-023

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Various aspects of interactions between tall fescue and ladino clover were observed in the presence and absence of O3. Ozone reduced the growth of clover and fescue seedlings. Fescue seedlings were less sensitive to O3than were clover seedlings. Leaf leachate from transplanted fescue plants inhibited the growth of clover. Nodulation of clover was reduced by leachate from fescue plants exposed to O3, but not by leachate from nonexposed fescue plants. The addition of fescue, clover, or fescue and clover debris to soil stimulated the growth of both clover and fescue. This stimulation was reduced or eliminated by O3. Root interactions of seedling fescue and clover had little effect on clover, but transplanted fescue and clover root interactions reduced the growth of clover. The direct and indirect effects of O3and (or) fescue on clover are discussed.

ISSN:0008-4026    

DOI:10.1139/b80-024

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Aldehyde fixation ofAbutilonnectaries induces deposition of callose, probably at plasmodes-mata. The phenomenon was analysed by examining a range of other tissues, several of which show a similar response, and by varying the fixation conditions. Callose deposition occurs within 15 min of the onset of fixation in immature nectaries, and does not occur in mature nectaries. Low temperature controls show that the deposition is artefactual and that it may give an erroneous view of the structure of plasmodesmata.

ISSN:0008-4026    

DOI:10.1139/b80-025

出版商:NRC Research Press    

年代:1980

数据来源: NRC