摘要:

A study was made of several factors influencing the growth and survival of rhizobia in humus and soil cultures. Screw-capped glass jars were more satisfactory than the foil-lined cardboard cartons used commercially for packaging of seed inoculation cultures because contaminants were excluded and moisture retained more effectively. Refrigeration of the cultures reduced water losses and proved to be an excellent method of maintaining large numbers of living bacteria for a long time. The addition of sucrose to the humus cultures ordinarily produced large increases in numbers of rhizobia, as determined by plate counts, and the addition of various inorganic nutrients generally produced smaller increases. In general, any particular element stimulated growth only if the level of that element in the soil used as a base was below optimum. Nitrate and sucrose stimulated growth when either was used alone, but together they greatly depressed growth.

ISSN:0008-4026    

DOI:10.1139/b53-022

出版商:NRC Research Press    

年代:1953

数据来源: NRC

摘要:

Bacillus subtilis(Ford's type) was able to fix only 3% of the NaHC14O3added during anaerobic dissimilation of glucose, under conditions whereSerratia marcescensandAerobacter aerogenesfixed 38% and 54% respectively. The carbon-14 was found mainly in succinic acid, lactic acid carboxyl, and formic acid, in decreasing order of specific activity. Similar experiments with labelled formate showed it to be relatively inert, most of it being recovered unchanged. Acetate was readily metabolized byB.subtilisduring the fermentation of glucose with a marked increase in the amount of 2,3-butanediol and ethanol formed, while the amount of glycerol was decreased to less than one-tenth of the normal value. Experiments with CH3C14OONa proved that the acetate was reduced to ethanol, only traces of acetate carbon being found in 2,3-butanediol or lactic acid. Fermentation of glucose-1-C14gave 2,3-butanediol and lactic acid labelled in the methyl groups and glycerol labelled mainly in the primary alcohol groups; only a small part of the carbon-14 being found in carbon dioxide.

ISSN:0008-4026    

DOI:10.1139/b53-023

出版商:NRC Research Press    

年代:1953

数据来源: NRC

摘要:

Microbiological studies involving the use of three soil fumigants, methyl bromide, a propane–propene mixture, and ethylene dibromide, established a biological basis for the evaluation of soil fumigants as fungicides, bactericides, and actinomycides and provided quantitative and qualitative data from which the efficacy of each fumigant was rated as high, medium, low, and poor in each capacity and permitted a study of the significance of population trends. Due emphasis was placed on the two factors, concentration of the fumigant and the period of confined exposure, by determining the value of each factor required to produce, under controlled conditions of temperature and soil moisture, a 90% reduction in numbers of each microbiological group. Methyl bromide proved to be the most effective fumigant in all three capacities while ethylene dibromide formulations were least effective. The concentrations of, and exposure periods to, ethylene dibromide and the propane–propene mixture required to give satisfactory reduction of the three microbiological populations are considered high and neither fumigant is recommended as a fungicide, bactericide, or actinomycide. However, ethylene dibromide proved to be more effective than methyl bromide against root-knot nematodes and is recommended for use in this capacity. Soil fumigation effectively altered the microbiological balance in favor of fungi that were normally suppressed by a predominance of aspergilli and penicillia. Of four physiological groups of bacteria studied, nitrifiers and cellulose decomposers were most severely reduced in numbers by methyl bromide fumigation. The actinomycetes showed a greater tolerance of fumigation than either the fungi or bacteria.

ISSN:0008-4026    

DOI:10.1139/b53-024

出版商:NRC Research Press    

年代:1953

数据来源: NRC

摘要:

Quantitative and qualitative studies were made of the fungi in the air over various parts of Canada and Alaska, continuing studies in arctic aerobiology. In winter, arctic air is apparently sterile: in summer, at Ft. Churchill, Man., ground level samples varied from 0.5 to 4.4 per cu. ft.Cladosporiumwas the commonest fungus (average 0.5 per cu. ft.), followed by yeasts (0.16),Penicillium(0.06), andStemphylium(0.03 per cu. ft.). Other fungi present werePullularia,Botrytis,Aspergillus,Verticillium,Pyrenochaete,Helminthosporium,Phyllosticta,Papularia,Cunninghamella, andSporormia. Of 3711 colonies 57% failed to sporulate. Silicone slide readings as high as 114.9 fungus spores per cu. ft. were obtained and included the following: yeasts (8.6),Cladosporium(3.8), smuts (2.5),Fusarium(0.6),Alternaria(0.06 per cu. ft.),Venturia,Cercospora,Septoria, rusts,Leptosphaeria,Sordaria, andPleosporaand many hyaline one-celled spores. In two flights to Resolute Bay, N.W.T., the flora was found to be similar to that at Ft. Churchill but numbers did not exceed 1 per cu. ft., although readings up to 78 fungus spores per cu. ft. were recorded on slides in warm air over Hudson Bay. Most of the fungi are considered to be soil types originating in agricultural areas and carried northward by southerly winds. The majority are no longer viable when they reach the arctic. There is evidence that the numbers of fungi are correlated with air masses, not only in the arctic but also in air over other parts of Canada.

ISSN:0008-4026    

DOI:10.1139/b53-025

出版商:NRC Research Press    

年代:1953

数据来源: NRC

摘要:

Movement of rubidium86and calcium45injected into the trunks of yellow birch and white pine was followed with a newly-developed portable scintillation counter. Maximum rate of upward movement of the rubidium86in the xylem of yellow birch approximates one foot per minute along a narrow channel spiralling upward (usually dextrally) from the point where the isotope was first introduced. Movement in decadent yellow birch was very slow with an apparent increase of permeability of the bark tissue as indicated by lateral diffusion of the isotope. In October no upward movement was discerned in healthy trees but rather an active downward translocation in the phloem.

ISSN:0008-4026    

DOI:10.1139/b53-026

出版商:NRC Research Press    

年代:1953

数据来源: NRC

摘要:

Four separate investigations of decay in balsam fir (Abies balsamea(L.) Mill.) have been carried out in recent years by forest pathologists in Eastern North America. Early in these studies it became apparent that the existing ideas concerning the identity of the fungi responsible for decay in living balsam fir trees required considerable revision. Trunk rot was confirmed as being caused mainly byStereum sanguinolentumAlb. and Schw. ex Fries; however, five fungi, headed byCorticium galactinum(Fries) Burt, were found associated with most of the white stringy butt rots, and two fungi,Coniophora puteana(Schum. ex Fries) Karst. andPolyporus balsameusPeck, were associated with most of the brown cubical butt rots. HithertoPoria subacida(Peck) Sacc. andP.balsameuswere believed to cause practically all white and brown butt rots, respectively, in this species. The effect of site on the decay of living balsam fir is discussed, as is the extent and kind of decay with which each of the nine predominant heart-rot fungi was found associated. A brief outline is presented concerning the fungi found associated with the deterioration of dead balsam fir.

ISSN:0008-4026    

DOI:10.1139/b53-027

出版商:NRC Research Press    

年代:1953

数据来源: NRC