摘要:

The greenish-brown margin of discolored wood in three living silver maple trees,Acer saccharinumL., was examined by scanning electron microscopy and microbiological culture techniques. Micrographs of xylem vessels revealed filamentous structures; some of them appeared to be actinomycetous hyphae. Actinomycetes identified asStreptomyces parvullusWaksman & Gregory,S.sparsogenesOwen, Dietz & Camiener, and a thirdStreptomycesstrain were isolated repeatedly from discolored wood of each tree. These isolates grew in liquid media in the presence of 0.1% (w/v) concentrations of several phenols. Although other phenols included in the test were not substantially degraded,p-hydroxybenzoic acid was utilized as a carbon source byS.parvullus. All three actinomycetes inhibited growth of selected wood-inhabiting fungi when paired on malt agar. When inoculated on sterilized sapwood and discolored wood from silver maple, the actinomycetes colonized vessel walls and occlusions, but were not observed to decay cell walls.

ISSN:0008-4026    

DOI:10.1139/b81-001

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Young pepper plants treated with gibberellic acid (GA3) before the initiation of floral organs produced abnormalities in flowers subsequently formed. The development of petals and stamens was affected by GA3, but sepals and the gynoecium were insensitive to the treatment. The effect on petals was on the unrolling of organs but stamen development was affected more dramatically. GA3caused abnormalities in pollen development and induced the carpelization of stamens. The expression of feminization of stamens ranged from the production of a few external ovules to a complete transformation of a stamen to a carpel with ovary, style, and stigma. In some instances, the growth of stamens was also inhibited. GA3also induced supernumerary organs in flowers; all of which were "carpel-like." These and other observations are discussed in relation to the hormonal status and the genetic make-up of plants.

ISSN:0008-4026    

DOI:10.1139/b81-002

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The correct taxonomic position ofSolidago ptarmicoides(Nees) Boivin has long been debated. The abundance of hybrids between this taxonand species ofSolidago, especially species of Sect.Oligoneuron, suggests an affinity with this group. The white colour of florets in this taxon could be due to a mutation interfering with synthesis of the flavonoids accounting for the yellow color inSolidago. In our study of the genusAster, we found that phyllary morphology is a very clear character for excludingA.ptarmicoidesfrom the genusAsterand including it intoSolidago. This conclusion is suported by other morphological features, such as habit and leaf anatomy, and is strengthened by geographical, ecological, and chromosomal data. It is, therefore, suggested that this taxon be definitely removed from the genusAsterand included inSolidagoSect.Oligoneuron. The following new combination is proposed:Solidago×luteus(= ×Solidaster hybridus, ×S.luteus).Solidasterand ×Asteragoare reduced to synonyms underSolidago.

ISSN:0008-4026    

DOI:10.1139/b81-003

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Using light and electron microscopy,Gliocladium virensis proved to be a hyperparasiteof Rhizoctonia solani. When hyphae ofG.virenscome in contact with those ofR.solani, the following sequence of events are observed (i) contact ofG.virenswith host cells, (ii) formation of appresoria, (iii) penetration of host cells, (iv) formation of intracellular hyphae, and (v) collapse and death of host cells.In vitro,G.virenseffectively inhibited sclerotial formation ofR.solani.Greenhouse tests showed that the presence ofG.virensin soil artificially infested withR.solanireduced at planting the severity ofRhizoctoniaroot rot in white beans. Root rot severity decreased with increasing concentrations ofG.virens. A similar result was obtained in soil treated with the two fungi 2 months prior to planting. This study suggests thatG.virensmay be a promising biological control agent forRhizoctoniaroot rot of white beans.

ISSN:0008-4026    

DOI:10.1139/b81-004

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The effects of position and age of leaves on CO2exchange rate (CER) are described for a single-cross corn (Zea maysL.) hybrid ('Harrow 691') grown at 10-h and 20-h photoperiods. The effect of leaf age is also described for barren plants grown at a 10-h photoperiod.CER of newly matured leaves increased from leaf 3 to leaf 6 (10 h) or 8 (20 h). The rates were not significantly different for leaves 6 to 13, but were lower for leaf 14, at 10 h; while the rate for leaf 10 was lower than for leaf 8 but not different from that for leaves 11–15, at 20 h.CER declined with leaf age, but the rate of decline was reduced after pollination at both 10 h and 20 h. The stomatal resistance changed little for a period of 4 to 5 weeks following silking. The decline in CER of all leaves studied for barren plants was smooth, with the rate being unaffected in the postsilking period; in these plants changes in stomatal resistance closely reflected the decrease in photosynthetic rates.The results emphasize that the CER of newly matured leaves was lower for leaves produced in the early stages of ontogeny than for those maturing later, and that the pattern of decline with age in photosynthetic activity varied considerably amongst those leaves that would have been contributing assimilates to the developing ear.

ISSN:0008-4026    

DOI:10.1139/b81-005

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Symbiotic associations were established between nitrogen-fixing nonleguminous (actinorrhizal) snowbrush (Ceanothus velutinusDougl.) seedlings and two categories of microorganisms: vesicular–arbuscular (VA) mycorrhizal fungi and a filamentous actinomycete capable of inducing nodule formation. The actinomycete is housed in nodules where fixation of atmospheric dinitrogen occurs and is made available to the host plant; the mycorrhizal fungus is both inter- and intra-cellular within the root tissue and may be found within the nodules. The two major nutrients, N and P, are made available and can be supplied to the host plant by these two symbiotic microorganisms. The root system of snowbrush seedlings was dually colonized by VA mycorrhizal fungi and a nitrogen-fixing actinomycete and the possibility of a direct interaction between the endophytes in the symbioses was investigated. Dually infected plants showed increases in total dry weight of shoots and roots, number of nodules, weight of nodular tissue, as well as higher levels of N, Ca2+, and P, and an increase in nitrogenase activity as measured by acetylene reduction.

ISSN:0008-4026    

DOI:10.1139/b81-006

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The perithecial development ofHypoxylon serpens(Pers. ex Fr.) Kickx in artificial culture is described. Perithecia develop from initials formed within the vegetative mycelium. Perithecial initials include an ascogonium and surrounding envelope. The ascogonium gives rise to ascogenous elements and eventually asci. The envelope gives rise to all sterile structures, including paraphyses and pseudoparenchyma. Features ofHypoxylon serpensperithecia are representative of theXylaria-typecentrum. The relationship of theXylaria-typecentrum with some other centra is discussed.

ISSN:0008-4026    

DOI:10.1139/b81-007

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Daytime stomatal conductance of McIntosh apple leaves was variable and relatively high (1.4 to 3.8 mm s−1) up until fruit removal. Leaf chlorophyll content, total leaf water potential, and specific leaf weight were less variable. Stem water content declined linearly by 10% from mid-August to late October. After fruit removal stomatal conductance, leaf chlorphyll content, and total leaf water potential decreased to low levels. Specific leaf weight did not decline until very late in leaf senescence.A simple model of stomatal response to environmental factors was tested and, following calculation of appropriate parameter values, gave acceptable agreement between measured and calculated stomatal conductances.

ISSN:0008-4026    

DOI:10.1139/b81-008

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The phototoxicity of polyacetylenes from representatives of the Asteraceae to a broad range of freshwater and marine algal species was observed. In the tests triacetylenes were more toxic than diacetylenes. In addition, a small group of polyacetylenes with terminal alcohol or aldehyde groups were found to be toxic with or without ultraviolet (UV) treatment (300–400 nm). Quantitative tests withEuglenaandValoniaindicated toxic reactions with three compounds at concentrations greater than 1 ppm. Considering the toxicity of polyacetylenes to bacteria, fungi, invertebrates, and fish, the present work with plants is further evidence of their general cytotoxic nature.

ISSN:0008-4026    

DOI:10.1139/b81-009

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Light and scanning electron microscopy ofEpicoccumaleuriospores substantiate reports that these spores are forcibly released. Our observations of thin, protruding cross walls between the stalk and adjoining basal cell of the spore, and the circumscissile fracture of the rough outer sheath of the stalk are indicative of an active mechanism of spore release inEpicoccumrather than the passive, lytic mechanism suggested by other workers.

ISSN:0008-4026    

DOI:10.1139/b81-010

出版商:NRC Research Press    

年代:1981

数据来源: NRC