摘要:

Four distinct types of colonial mutation were obtained by X-ray irradiation of a parasitic strain of alfalfaRhizobium. Two types were procured from an effective strain. Colonial morphology remained stable throughout serial transfer on artificial medium, but changed considerably after one plant passage. Three variants derived from the parasitic parent were found to be efficient in nitrogen fixation when tested by sterile plant growth procedures and the Virtanen technique. This efficiency increased during the course of two plant passages. Colonial variation and effectivity changes occurred independently of one another.

ISSN:0008-4026    

DOI:10.1139/b52-010

出版商:NRC Research Press    

年代:1952

数据来源: NRC

摘要:

The gaseous exchange accompanying decomposition of dithiocarbamate fungicides was measured in the Warburg manometer. Sodium diethyl dithiocarbamate decomposed under slightly acid conditions, producing carbon disulphide and a salt of diethylamine. The insoluble zinc and iron salts of dimethyl dithiocarbamic acid also decomposed in a similar fashion, but no carbon disulphide was given off from the more stable copper salt of this compound. The rate of decomposition of these metallic salts fell in the following decreasing order:Disodium ethylenebis-dithiocarbamate (nabam) decomposed under slightly acid conditions to produce approximately equal volumes of hydrogen sulphide and carbon disulphide, and presumably left a residue of ethylene thiourea. In distilled water, on the other hand, nabam underwent a slow basic hydrolysis and oxidation, with absorption of approximately two volumes of oxygen, and evolution of one volume of carbon disulphide. Apparently the sulphur fraction which is evolved as hydrogen sulphide from nabam under acid conditions is, under basic conditions, oxidized in solution by atmospheric oxygen to sulphate.

ISSN:0008-4026    

DOI:10.1139/b52-011

出版商:NRC Research Press    

年代:1952

数据来源: NRC

摘要:

A study has been made of the comparative X-ray sensitivity of cells of diploid and tetraploid species ofTradescantiaat two different resting stages during the development of the pollen grains. At the resting stage midway between meiosis and the pollen grain division, no significant difference was found in the number of breaks per chromosome in the two species. At the resting stage just following the pollen grain division, the tetraploid chromosomes showed a slightly higher break frequency, a difference which was statistically significant. This increase was due, at least in part, to the presence of a small portion of cells which showed an abnormally high sensitivity. From a detailed study of the cells at each stage and the types of aberrations induced it is concluded that the chromosomes of each species are of equal sensitivity, and that any difference in the reaction of the diploid and tetraploid cells to irradiation is due simply to the numerical difference in the chromosomes of the cells, or to differences in the nuclear stage when X-rayed.

ISSN:0008-4026    

DOI:10.1139/b52-012

出版商:NRC Research Press    

年代:1952

数据来源: NRC

摘要:

A halophilic coccus,Micrococcus halodenitrificansn. sp., isolated from meat curing brines is described. This organism grows optimally in media containing between 4.4 and 8.8% sodium chloride as determined by viable counts and manometric methods. The viable count decreases in media containing 2.2% or less sodium chloride. As salt concentrations increase above 8.8%, the length of the lag phase increases and the rate of growth decreases. The organism exhibits a specific sodium chloride requirement for growth. However, it continues to respire in the presence of sodium bromide.

ISSN:0008-4026    

DOI:10.1139/b52-013

出版商:NRC Research Press    

年代:1952

数据来源: NRC

摘要:

WithMicrococcus halodenitrificans, maximum production of nitritase occurs just after nitrite has been reduced completely to nitrogen. Maximum denitrifying activity takes place at pH 7.6 in the presence of 0.38 to 0.75 molar sodium chloride or sodium bromide. The activity is slightly less in the presence of lithium chloride but reaches a peak at 0.19 to 0.38 molar concentration. The reduction of nitrate to nitrite is inhibited by azide whereas reduction of nitrite to nitrogen is not, suggesting the possibility that at least two separate enzymes may be involved in these reactions. The lactic acid dehydrogenase of this organism shows maximum activity in the presence of 0.75 molar sodium chloride.

ISSN:0008-4026    

DOI:10.1139/b52-014

出版商:NRC Research Press    

年代:1952

数据来源: NRC

摘要:

Tests made at regular intervals over a period of 10 years on naturally infested seed of wheat, oats, and barley that had been held in storage showed that most of the seed, while retaining its germinability, became free from viable fungi before the end of the storage period.Alternaria tenuis sensuWiltshire in all three crops,Helminthosporium sativumP.K. & B. in wheat and barley, andSeptoria nodorumBerk, in wheat died out comparatively rapidly.H.avenaeEidam in oats andH.teresSacc. in barley lost their viability slowly and since, by the end of the storage period, most of the microorganisms associated with them in infested kernels were dead, these two fungi could generally be recovered in pure culture.

ISSN:0008-4026    

DOI:10.1139/b52-015

出版商:NRC Research Press    

年代:1952

数据来源: NRC

摘要:

Trends in variation in different parts of the tree with regard to such anatomical features as tracheid and ray cell dimensions, size and distribution of rays, size and arrangement of pits, and thickness of cell walls resemble those recorded for other Cupressaceae. Comparative data relating to homologous wood samples show slight differences in mean values between the three American species ofChamaecyparis, but the intraspecific variability is usually so extensive that the specific ranges overlap widely. No single microscopic character seems completely reliable for diagnostic purposes, but certain structural features are valuable when used together. These are the frequency of ray tracheids in newly formed rays, the thickness of the horizontal and end walls of ray parenchyma cells, the number of pits per crossing field, and the height/width ratio of ray cells viewed tangentially.

ISSN:0008-4026    

DOI:10.1139/b52-016

出版商:NRC Research Press    

年代:1952

数据来源: NRC

摘要:

Roots of water hyacinth (Eichhornia crassipes(Mart.) Soims.) and frogbit (Hydrocharis morsus-ranaeL.) when grown In solution cultures adjusted to pH 3.5, 4.0, 5.0, 6.0, and 6.5 did not suffer decidedly adverse, direct effects from hydrogen ions except at extreme acidities represented by a pH value of less than 4. During cool weather the plants were able to grow at a somewhat higher concentration of hydrogen ions than was possible in the warm summer months. The boundary between good growth and toxicity was a narrow one. Extreme acidity, short of the critical point, inhibited the growth of the roots by decreasing cell division and cell elongation. In the roots investigated, cell division at pH 3.5 was reduced to one-half of the rate at pH 5.0 and this reduction accounted for three-quarters of the inhibition in the growth of the roots. When grown in a highly acid medium, root cells acquired a resistance to the hydrogen ions. Water hyacinth meristem cells from the highly acid media exhibited a pronounced resistance to hydrochloric acid. It is suggested that this increased resistance is due to the cells having acquired a greater impermeability to the acids. Determination of the pH of expressed root juices revealed that, although all of the saps were decidedly less acid than were the media in which the plants were grown, roots grown in an extremely acid medium had a slightly more acid sap than those grown in a less acid one. A comparison of rates of streaming and the action of protoplasts during plasmolysis indicated that extreme acidity in the growth medium increased the viscosity of the cytoplasm of root cells. No significant difference was noted in the osmotic pressure of the root cells from the different cultures. The absolute permeability of frogbit root hairs to thiourea, as calculated from the formula, did not vary significantly from.0012 millimoles per square centimeter of surface per hour per molar concentration difference for plants grown within the range of pH 3.6 to pH 6.0.

ISSN:0008-4026    

DOI:10.1139/b52-017

出版商:NRC Research Press    

年代:1952

数据来源: NRC

摘要:

During the present investigation, a total of 1579 seed samples of wheat, 1042 of barley, and 1152 of oats (100 kernels per sample), were examined microbiologically for the presence ofFusarium. Of these samples, 402 of wheat, 513 of barley, and 636 of oats originated in the seed inspection districts of Eastern Canada, and 1177 of wheat, 529 of barley, and 516 of oats in those of Western Canada. Isolates ofFusariumwere obtained from approximately 41.8% of the samples of wheat (1.5% of the kernels), 76.2% of the samples of barley (3.9% of the kernels), and 79.6% of the samples of oats (5.7% of the kernels) that originated in Eastern Canada, whereas only 13,8% of the samples of wheat (0.2% of the kernels), 36.3% of the samples of barley (0.7% of the kernels), and 38.9% of the samples of oats (1.1% of the kernels) from Western Canada yieldedFusarium. In classifying the different wild types ofFusariumthat were obtained from cereal seed the system of taxonomy and nomenclature of Wollenweber and Reinking was chiefly followed, but certain sections of the genus were revised extensively, partly in accordance with Snyder and Hansens' concept of species in this genus. Four new combinations are proposed, namelyF.compactum(Wr.) n. eomb.,F.lateritiumNees emend. Snyder & Hansen formacajani(Padwick) n. comb.,F.lateritiumNees emend. Snyder&. Hansen formacrotalariae(Padwick) n. comb., andF.oxysporumSchlecht. emend. Snyder & Hansen var.redolens(Wr.) n. comb. A total of 16 species and varieties ofFusarium, classified in nine sections of the genus, was isolated from cereal seed during this investigation. These species and varieties are, namely,F.poae(Pk.) Wr.,F.sporotrichioidesSherb.,F.avenaceum(Fr.) Sacc,F.arthrosporioidesSherb.,P.semitectumBerk. & Rav.,F.equiseti(Cda.) Sacc,F.acuminatumEll. & Ev.,F.culmorum(W. G. Sm.) Sacc,F.graminearumSchwabe,F.sambucinumFuckel,F.sambucinumvar.coeruleumWr.,F.lateritiumNees emend. Snyder & Hansen,F.moniliformeSheld. emend. Snyder&Hansen,F.oxysporumvar.redolens(Wr.) n. comb., andF.solani(App. & Wr.) Wr. emend. Snyder & Hansen.F.poae,F.avenaceum, andF.acuminatumwere most frequently isolated.F.concolorRg. andF.sambucinumf. 6 Wr,, that were previously recorded from cereal seed in Manitoba, and three additional species, namely,F.dimerumPenz.,F.merismoidesCda., andF.nivale(Fr.) Ces., that may be encountered in the future among isolates from cereal seed in Canada, were also included in this study.

ISSN:0008-4026    

DOI:10.1139/b52-018

出版商:NRC Research Press    

年代:1952

数据来源: NRC

摘要:

A method for preparing carbon and oxidation–reduction balances of aerobic fermentations is described. In spite of the complexity of the microbial cell, relatively few and simple analyses of the material are necessary for the purpose of constructing the balances. To test the method, balances were made on citric acid and ustilagic acid fermentations. Excellent results were obtained. Based on the principle of material balance, a number of formulae for calculating the fermentation efficiency and respiratory loss have been established for fermentations involving substrates and products of varied oxidation–reduction status. Limitations of the method and formulae are also discussed. Results obtained by the described methods and equations are of value in correlating the various processes occurring in an aerobic fermentation and in providing an over-all picture of the fermentation.

ISSN:0008-4026    

DOI:10.1139/b52-019

出版商:NRC Research Press    

年代:1952

数据来源: NRC