摘要:

In the taxa that constituteCrataegus crus-galliL.sensu latoshort-shoot leaves vary progressively from node to node in both size and shape. The pattern of this variation may differ not only between taxa but also within taxa, among local stands. Failure to recognize such variation may confound taxonomic studies based on leaf shape, judging from the results of parallel canonical variates analyses differing in whether or not sampling was stratified by leaf position. With the incorporation of such stratification into the sampling design, however, leaf descriptors provide a valuable source of data for studies of group differentiation inCrataegustaxa.

ISSN:0008-4026    

DOI:10.1139/b84-241

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Thirteen populations ofSorghum halepense, Johnson grass, were sampled from fields in Ontario, Canada, and Ohio and New York, United States. Only four of these populations were reported to overwinter as rhizomes. The morphology, phenology, resource allocation patterns, and growth of seedling and mature plants of the overwintering and the non-overwintering populations were compared. Field-collected specimens from the nonoverwintering populations had wider culms and leaves and larger seeds and inflorescences. Analysis of material grown in a 5-month greenhouse trial indicated similar differences. Greenhouse plants from the nonoverwintering populations were also characterized by greater percent emergence, larger and faster growing seedlings, earlier flowering, larger culms and seeds, greater reproductive dry weight per plant, and about 1/10th the rhizome dry weight of overwintering plants. Differences between populations within a biotype were evident for both biotypes, although there was little within-population variation, except in rhizome production, where certain individuals of some nonoverwintering populations did not produce extended rhizomes. Among the five enzymes which were examined electrophoretically, only one, phosphoglucomutase (PGM), showed variable isozyme patterns. No differences in enzyme patterns were apparent between the overwintering and the nonoverwintering biotypes. The relationship of the nonoverwintering populations to the cultivated species,Sorghum bicolorandS.almum, an introgressant betweenS.halepenseandS.bicolor, is discussed.

ISSN:0008-4026    

DOI:10.1139/b84-242

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Embryos and young plants of tomato, radish, and red cabbage germinated in different media showed an ascending degree of tolerance to NaCl. Red cabbage embryos were tolerant to salinity and showed the highest K+and Ca2+fixation capacities which were correlated to the lowest initial adsorption of Na+. Furthermore, initial accumulation of K+and Ca2+in red cabbage was increased with increasing NaCl in the medium. Conversely, salt-sensitive tomato embryos showed the lowest initial internal ratios of Ca2+/Na+and K+/Na+, and increasing NaCl concentrations did not provoke any increase in contents of K+and Ca2+. No correlation was found between tolerance to salinity and Na+content of young plants. However, Ca2+accumulation capacity in a (NaCl + CaCl2) medium was associated with the degree of tolerance, although the ratio of internal Ca2+/Na+decreased. In tomato and red cabbage, a competitive interaction was found between K+and Na+at high salt concentrations, while in radish allosteric interactions were observed. Thus, radish accumulated more K+than Na+at high KCl and NaCl concentrations and young plants of radish and red cabbage had the highest selectivity for potassium. Plant tolerance to salinity, during seed germination, was correlated to accumulations of K+and Na+in embryos. The mobilization of Ca2+stored in the seed does seem to have a regulatory role in the plasmalemma selectivity.

ISSN:0008-4026    

DOI:10.1139/b84-243

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

The function of diatom mucilage in the formation of spatially complex periphyton communities was investigated in McConaughy reservoir (Nebraska, U.S.A.). Seasonal biofilms on natural and artificial substrates revealed high densities of periphytic diatoms (up to 3.5 × 104 cells mm-2). Growth habits of the dominant taxa (short stalk,Achnanthes minutissima; long stalk,Cymbella affinisandGomphonema olivaceum; rosette,Fragilaria vaucheriaeandSynedra radians) depend on the mucilage morphology. The volume of stalk mucilage in late stages of community development was estimated to be more than two times the volume of the cells producing it. When the periphytic biomass exceeded the carrying capacity of its substrate, portions of the community were sloughed, resulting in the loss of the upper story of cells and mucilage. Diatom mucilage affects community structure as follows: (i) it allows cell–surface adhesion; (ii) stalks ofCym.affinisprovide increased surface area for attachment byAch.minutissima; (iii) dense canopies of long-stalkedCym.affinisandGomphonema olivaceumtrap euplanktonic algae which have settled into the periphyton; (iv) mucilage binds detrital particulates; (v) stalked diatoms enable vertical stratification in the community, as spring collections revealed the development of an upper tier composed ofGomphonema olivaceumandCym.affiniscovering a lower tier dominated byF.vaucheriaeandStephanodiscus minutula.

ISSN:0008-4026    

DOI:10.1139/b84-244

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

During the 1981 and 1982 growing seasons,Aureobasidium pullulans(de Bary) Arnaud andChaetomium globosumKunze: Fr. spore suspensions were applied to apple saplings in an orchard at 1- to 2-week intervals to control the apple scab pathogen,Venturia inaequalis(Cke.) Wint. (anamorph,Spilocaea pomiFr.). Population densities of applied antagonists were monitored during 1982 trials by dilution plating of leaf washings onto selective media.Aureobasidium pullulansandC.globosumpopulations averaged 54 and 314 colony-forming units (CFU) per milligram of leaf tissue 3 h after application and declined to means of 15.9 and 35.7 CFU mg−1, respectively, before the next application. Relative to buffer controls, spore suspensions ofA.pullulanswere only slightly antagonistic toV.inaequalisinfection, butC.globosumascospore suspensions reduced scab more than 20% in both years. Light and scanning electron microscope examination of leaf surfaces following inoculation of seedlings in growth chambers showed a 25% increase inC.globosumascospore germination on scab-infected tissue relative to healthy tissue. The minimum concentration ofC.globosuminocula effectively reducing apple scab in growth chamber experiments was approximately 1 × 106ascospores mL−1.

ISSN:0008-4026    

DOI:10.1139/b84-245

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Ascospore suspensions and culture extracts ofChaetomium globosumKunze: Fr. reduced infection of apple seedlings byVenturia inaequalis(Cke.) Wint. (anamorph,Spilocaea pomiFr.) in growth-chamber studies. An agar diffusion assay was developed to assess the relative fungistatic activity of culture extracts ofC.globosum. No differences were observed in the sensitivity of 37V.inaequalisstrains toC.globosumextracts. Seven strains ofC.globosumfrom diverse habitats were evaluated for antibiotic production in culture. Significant differences in antibiotic production between strains were observed, and antibiotic levels were positively correlated with antagonism toV.inaequalison seedlings in growth-chamber studies. The antibiotic chetomin was tentatively identified in culture extracts by thin-layer chromatography and ultraviolet absorbance. The selection of high antibiotic producing strains ofC.globosummay significantly improve antagonistic performance in the field.

ISSN:0008-4026    

DOI:10.1139/b84-246

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Changes in nitrogen, calcium, water-soluble compounds, and total available carbohydrate in decomposing leaf litter of six tree and one shrub species, enclosed in nylon net bags and placed in a mixed oak conifer forest, were examined for a period of 487 days. The concentration of nitrogen increased during decomposition in all litter species. This increase was up to threefold inAesculus indica,Quercus floribunda, andQuercus leucotrichophora. In most species the absolute increase in nitrogen mass was observed when decomposition had progressed up to 213 days. However, inDaphne cannabinaandIlex dipyrena, the absolute mass of nitrogen was never greater than the initial mass at any stage of decomposition. The absolute mass of calcium in litter bags generally declined with time. The concentration of water-soluble compounds and of total available carbohydrates varied from species to species; both these constituents, however, continually decreased with the progress of decomposition. Within 1 year, the release of nitrogen, water-soluble compounds, and total available carbohydrates was 100% inD.cannabina,A.indica, andI.dipyrena. InCedrus deodara,Q.floribunda, andQ.leucotrichophoraabout 50% of total nitrogen input to the forest floor as litter fall was released by decomposition. InCupressus torulosaonly 14% of nitrogen falling as leaf litter was released during a period of 1 year.

ISSN:0008-4026    

DOI:10.1139/b84-247

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Germination tests have been carried out on seeds of a Mediterranean population of sea fennel (Crithmum maritimumL.) collected from plants in Santa Margherita di Pula, in the southwest of Sardinia, Italy. Germination was evaluated in the dark at different temperatures and at various salt concentrations. The optimal conditions for germination were a constant 20 °C in deionized water or at a very low salt concentration. These conditions are strikingly different from those necessary for the germination of seeds from the Atlantic coast (Meadfoot Bay, England). The presence of dormancy in the seeds is analyzed and discussed in terms of ecophysiological control and mechanisms which prevent germination under adverse environmental conditions.

ISSN:0008-4026    

DOI:10.1139/b84-248

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Lophophacidium dooksiin. sp. (Phacidiaceae) occurring on needles ofPinus strobusL. is described, illustrated, and compared withLophophacidium hyperboreumLagerberg, the type species. Ascomata ofL.dooksiimature during the spring and summer on attached 2nd-year needles.

ISSN:0008-4026    

DOI:10.1139/b84-249

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

MitteriellaandQuestieriellasynanamorphs ofSchiffnerula barnadesiaeare illustrated, described, and compared with those of two other species, namelyM.ziziphinaandM.ziziphi-rugosae.Clypeolella ziziphina, the teleomorph ofM.ziziphina, is transferred toSchiffnerula.

ISSN:0008-4026    

DOI:10.1139/b84-250

出版商:NRC Research Press    

年代:1984

数据来源: NRC