摘要:

Ascospore and spore appendage ultrastructure inPleospora gaudefroyiis described. Ascospore walls comprise a three-layered mesosporium within which electron-dense bodies (melanin?) are deposited in two layers (W2, W3), a tripartite episporium (W4), and an outer mucilaginous sheath (exosporium?). The electron-dense inclusions in the mesosporium are compared with those in the conidia ofAlternaria brassicicolaand ascospores ofCarbosphaerella leptosphaerioides. In the unitunicate marine Ascomycetes, ascospores with a sheath are uncommon, whereas in the Loculoascomycetes many species have such ascospores. The sheath inP.gaudefroyiis compared with those ofParaliomyces lentiferus,Massarina thalassiae, andMassarina armatispora(all Loculoascomycetes).Key words: appendage ontogeny, marine Ascomycotina, taxonomy, ultrastructure.

ISSN:0008-4026    

DOI:10.1139/b94-001

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Infection of malformed and nonmalformed mango (Mangifera indica) trees byFusarium subglutinanswas assessed in Florida. All malformed floral panicles, but only 50% of the nonmalformed panicles, were infected by the fungus. When within-panicle infection was evaluated, an average of 84.5 % of the small pedicel and peduncle tissue pieces from malformed panicles were infected. When malformed and nonmalformed panicles were both assessed, 68.3% of the tissues from malformed panicles, but only 11.7% from nonmalformed panicles, were infected. Slight infection (2.2%) was observed in branch tissue that supported malformed panicles, and the fungus was never isolated from branches that supported nonmalformed panicles. In nutritional complementation tests with nitrate nonutilizing (nit) mutants, 55 of 64 isolates ofF.subglutinansfrom malformed mango panicles were in the same vegetative compatibility group. The data indicate that mango malformation in the study area was significantly correlated (P < 0.0001) with infection by genetically related populations ofF.subglutinans. The far greater prevalence ofF.subglutinansin malformed than in asymptomatic panicles suggests that malformation symptoms develop in floral tissues only after they are extensively colonized by this fungus.Key words:Fusarium subglutinans, mango malformation, vegetative compatibility.

ISSN:0008-4026    

DOI:10.1139/b94-002

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Variation in life-history traits such as emergence, survival, time of flowering, and fecundity were studied inDiplotaxis erucoides, a mediterranean winter annual weed, by analyzing cohorts that emerged in autumn, early spring, and spring. The response of the plants to the environment, as reflected by plant architecture and pattern of biomass allocation, was also studied. Seedlings that germinate in autumn produced from 3 to 10 times more seeds than those that germinated in spring. The main factor affecting the number of seeds produced appears to be the life-span. Reduction of the growing period led to a decrease in both number and length of modular units, which resulted in decreased numbers of leaves, flowers, and fruits of each module. In semelparousD.erucoidesplants, differences in the pattern of biomass allocation to reproduction are related to plant size. Our field data indicate that an increase of reproductive effort with size occurs in small individuals; however, a decrease occurs for vegetative biomass greater than 2 g and less than 5 g. Little variation in reproductive effort occurs when vegetative biomass is greater than 5 g. From a strategic point of view, size-dependent variation of reproductive effort inD.erucoidescan be interpreted as good tactics to favour a higher proportion of resources devoted to reproduction in small individuals, thus ensuring some offspring. However, structural, developmental, and physiological constraints lead to stabilization or even a decrease in reproductive effort above a certain threshold size, when production of offspring is already ensured.Key words: phenotypic plasticity, plant architecture, biomass allocation,Diplotaxis erucoides.

ISSN:0008-4026    

DOI:10.1139/b94-003

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

The new speciesPenicillium kananaskenseis described based on an isolate from soil in aPinus contortaforest from Alberta, Canada. Colonies are characterized by their relatively rapid growth, velutinous texture, white to slightly pink conidial masses, growth at 5 °C, and absence of growth at 37 °C. The conidiophores are monoverticillate or have one metula, are up to 300 μm tall, smooth walled or with slightly roughened walls, vesiculate, and bear ampulliform phialides, 8–11.5(−14.5) × 2.5–4 μm, that produce disordered chains of ellipsoidal conidia, 3–5 × 2.5–4 μm, with smooth or finely roughened walls. The species is compared with previously described taxa and its subgeneric affinities are discussed. Preliminary data on the many secondary metabolites produced by the ex-type culture are presented.Key words:Penicillium kananaskense, soil,Pinus contortavar.latifolia, mycotoxins.

ISSN:0008-4026    

DOI:10.1139/b94-004

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Further variations of the rotated-lamina syndrome are described inMagnoliaspp. andRhamnus imeretinus, as well as an abnormal adult shoot ofUlmus glabrawithout lamina rotation. All magnolias investigated show lamina rotation, but there are four possible forms of shoot symmetry: (i) dorsiventral distichous shoots with the form of rotated-lamina syndrome previously described, i.e., laminae of young leaves all face towards the same (upper) side of the bud or towards the parental axis in axillary buds; (ii) another form of dorsiventral symmetry in which lamina rotation occurs in the reverse direction; (iii) spiral phyllotaxis with laminae rotated to face up the genetic spiral; and (iv) spiral phyllotaxis with laminae rotated to face down the genetic spiral. Shoot symmetry and development of lamina rotation in leaf primordia correlate with the taxo-nomic subdivision of the genus. Shoots ofR.imeretinusare dorsiventral, with leaves arranged in four ranks, and lamina rotation occurs towards the upper side of the shoot. The sense of rotation of leaf primordia reverses with a periodicity of two plastochrons. In the abnormal shoot ofUlmuswithout lamina rotation, phyllotaxis was distichous and leaf primordia were symmetrical. The various cases are discussed in relation to the previously erected hypothesis that control of development in dorsiventral shoots with the rotated-lamina syndrome resides in alternating states of asymmetry in the shoot apex, and the corollary that a shoot with spiral phyllotaxis and one sense of lamina rotation should result if the state of asymmetry is maintained and does not alternate.Key words:Magnoliaspp.,Rhamnus imeretinus,Ulmus glabra, leaf, development, dorsiventrality, lamina rotation.

ISSN:0008-4026    

DOI:10.1139/b94-005

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Regeneration of salal (Gaultheria shallonPursh.) by seedling establishment and vegetative expansion was examined under various forest conditions in the central Coast Range of Oregon. Size and expansion rate of individual clonal fragments were negatively correlated with overstory stand density (p ≤ 0.039). As overstory basal area increased from 25 to 75 m2/ha, mean annual growth percentage of clone rhizome systems decreased from 23.7 to 0.0% and mean total rhizome length decreased from 102 to 0.89 m. Interclonal competition in dense clumps of salal apparently causes rhizomes to die and clones to fragment. In these patches, rhizome biomass and density, aerial stem biomass and density, and total biomass were negatively correlated with overstory density (p ≤ 0.01). For example, in clearcuts, salal clumps had up to 177.7 m rhizome/m2and 346 stems/m2, whereas patches under dense overstories had as few as 10.6 m rhizome/m2and 19 stems/m2. Aerial stem populations had uneven-age distributions of aerial stems in all overstory conditions. This structure is apparently maintained through annual production of new ramets. Salal seedling establishment rates were significantly affected by study site location, overstory density, and substrate (p ≤ 0.05). Two-year survival was highest on rotten logs and stumps in thinned stands.Key words: clonal morphology, clone populations, Douglas-fir forests,Gaultheria shallon, seedling establishment, vegetative expansion.

ISSN:0008-4026    

DOI:10.1139/b94-006

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Vegetative cover, fruiting phenology, and seed production was estimated from sixVacciniaheathlands on the Avalon Peninsula of Newfoundland so that the efficacy of theVacciniumseed bank could be ascertained. Out of the six species ofVacciniumpresent in this vegetation, onlyV.angustifoliumandV.borealewere recovered from 120 soil cores taken;V.uliginosumandV.vitis-idaea, two of the most common species on these heaths, were not represented in the seed bank at all, yet experimentally buried seeds from both these taxa will successfully germinate when exhumed after 6 years of burial. Indeed, 81% of the germinants were from taxa with dry fruits such asKalmia,Luzula,Juncus, andAgrostis. Paucity ofVacciniumseed in the soil column may be due in part to fungal rot and avian predation.Key words:Vaccinium, seed production, seed banks, heaths.

ISSN:0008-4026    

DOI:10.1139/b94-007

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Arnaudiella eucalyptorumis described as a new saprobic Ascomycete fromEucalyptusleaf litter. Its anamorph, which developed in pure culture, is placed in a new hyphomycetous genus,Xenogliocladiopsis.Xenogliocladiopsis eucalyptorumsp.nov. is known from collections ofEucalyptusleaf litter in the Transvaal and Cape provinces of South Africa, where it appears to be specific to this substrate.Key words:Arnaudiella eucalyptorum, Ascomycetes, Dothideales,Eucalyptusleaves, hyphomycetes,Xenogliocladiopsis eucalyptorum.

ISSN:0008-4026    

DOI:10.1139/b94-008

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Monoplastidic meiosis is reported for the first time in three seemingly unrelated liverworts, namelyBlasia pusilla(Metzgeriales),Monoclea gottschei(Monocleales), andHaplomitrium blumei(Haplomitriales). A second species ofHaplomitrium,H.hookeri, is polyplastidic as previously reported. All three taxa represent isolated relicts of ancient liverwort lineages. Monoplastidy in these hepatics is evident in archesporial tissue and is maintained through successive sporogenous cell generations. In archesporial mitosis, the single plastid divides and the two resultant plastids are precisely positioned so that one is inherited by each daughter cell. In the nascent spore mother cell, the solitary plastid undergoes two successive divisions and the resulting four plastids become positioned in a tetrahedral arrangement. Concomitantly, the sporocyte assumes a quadrilobed shape, which is less exaggerated inMonoclea, and a single large plastid is situated in each lobe. Details of plastid ultrastructure and morphology vary slightly among the three taxa. Evidence is presented thatBlasiaandMonocleashare a common ancestry and represent pivotal taxa in the evolution of the two main lines of liverworts.Haplomitriumis suggested to occupy a more basal position in bryophyte phylogeny. Monoplastidy in meiosis of liverworts links the charophytes, the three bryophyte clades, and the lycopsid pteridophytes and supports a monophyletic interpretation of land plant phylogeny.Key words: chloroplast, liverwort, meiosis, monoplastidy, phylogeny, sporogenesis.

ISSN:0008-4026    

DOI:10.1139/b94-009

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

The role of soil fungi andBacillusin the Chinese fir (Cunninghamia lanceolata) replant problem was investigated. Several pathogenic fungi isolated were more abundant in replant than in non-replant woodland soil, but the species composition of soil bacteria showed no significant differences. Fumigation of replant soils with methyl bromide significantly increased the growth of Chinese fir compared with nonfumigated soils. Inoculation of steam-sterilized soil with the pathogenic fungi caused significant reduction of growth of Chinese fir seedlings, while amendment with bacteria from the soil had no effect on seedling growth. However, the combination of pathogenic fungi and bacteria greatly reduced plant growth and increased root rot compared with pathogenic fungi or bacteria alone. It is suggested that fungi alone or in combination with bacteria may be important biotic factors in the Chinese fir replant problem.Key words: fungi, bacteria, Chinese fir, replanted soil, seedling growth.

ISSN:0008-4026    

DOI:10.1139/b94-010

出版商:NRC Research Press    

年代:1994

数据来源: NRC