摘要:

A study was made of the more specific amino acid requirements of bacteria from the rhizospheres of clover, flax, and wheat plants for which a chemically defined medium containing 23 amino acids provided essentials for maximum growth. Of seven groups of amino acids, the sulphur-containing group (cysteine, methionine, and taurine) was found to be of special significance, the omission of this group resulting in a pronounced decrease in the percentage of organisms able to develop. Further study of organisms dependent upon this group of amino acids for growth showed methionine to be by far the most essential compound. While evident for bacteria from the rhizosphere of all three crops, the effect was more pronounced in the case of clover than with flax or wheat.

ISSN:1923-4287    

DOI:10.1139/cjr50c-001

出版商:NRC Research Press    

年代:1950

数据来源: NRC

摘要:

The kinetics of the malic dehydrogenase in cell-free extracts of wheat seedlings have been studied by the Warburg technique, using methylene blue. The enzyme behaves analogously to the animal enzyme in that it is coenzyme I-linked and its oxidation product, oxalacetic acid, is inhibitory to the reaction. Oxalacetic acid is removed by either a ketone fixative orl(+) glutamic acid, the latter by being involved in a transamination. Cell-free extracts also contain peroxidase and ascorbic acid oxidase, but no phenolases. In embryonic tissue the succinoxidase system, including cytochrome oxidase, is present. Usingl(+) glutamic acid to remove oxalacetic acid, ascorbic acid can replace methylene blue and function as a respiratory carrier mobilizing the hydrogen from dihydrocoenzyme I indirectly via a pigment of unknown chemical nature. A proposed carrier system for the wheat plant includes coenzyme I, flavin, pigment, and ascorbic acid.In vitro, the entry of oxygen to the system is catalyzed by ascorbic acid oxidase supported by a thermostable copper-catalyzed reaction. Alcohol, hexosediphosphate, and fumarate can donate hydrogen to this carrier system.

ISSN:1923-4287    

DOI:10.1139/cjr50c-002

出版商:NRC Research Press    

年代:1950

数据来源: NRC

摘要:

Two species ofAleurodiscusoccurring on conifers, which have been under observation for several years, are described as new. Both are related toAleurodiscus roseus(Pers. ex Fr.) Höhn. & Litsch. The first, described asA.Minnsiaesp. nov., occurs most commonly onTsuga canadensisand is noteworthy because of an associated sclerotial disseminating phase of characteristic morphology, which has been known under the herbarium nameMinnsia carneaE. & E. ined. The history of our knowledge of this phase is given in some detail. The second species occurs onPinus Strobusand is described asA.Pinisp. nov. The known collections of both species are listed. Comparative culture work was conducted which showed that the two species are heterothallic, have a different growth rate, and are incompatible. They are also different from a form ofA.roseusoccurring onPopuluswhich proved to be homothallic.

ISSN:1923-4287    

DOI:10.1139/cjr50c-003

出版商:NRC Research Press    

年代:1950

数据来源: NRC

摘要:

Oxygen production by illuminated chloroplasts inp-benzoquinone solution proceeds most rapidly at neutrality, is more rapid with sorbitol borate than phosphate buffer, is insensitive to buffer molarity, and does not require carbon dioxide. In 0.08% quinone solution, the oxygen yields are 65 to 75% of the theoretical with crude spinach chloroplasts and 85 to 95% with separated chloroplasts. At concentrations above 0.08%, quinone strongly inhibits the photochemical reaction in which it serves as hydrogen acceptor, decreasing the total yield of oxygen as well as the initial rate of its production. Separation of the cell sap and cytoplasm from the chloroplasts by centrifuging and washing treatments largely eliminates dark reactions but also decreases photochemical activity in Hill and quinone solutions. Centrifuged chloroplasts have similar activities when resuspended in cell sap, distilled water, phosphate buffer, sucrose solution, or phosphate–sucrose solution. The supernatant fraction obtained by high speed centrifuging shows higher photochemical quotients in quinone solution and lower photochemical quotients in Hill solution than the chloroplast fraction diluted to the same chlorophyll concentration. The photochemical activity of crude and separated chloroplast suspensions in Hill and quinone solutions is inhibited to various degrees by 10−3Mazide and hydroxylamine, but not by 10−3Mfluoride. The presence of tannins or 2 × 10−3Madenosine triphosphate has no effect, but 1/10th saturated vitamin K weakly inhibits photochemical activity in quinone solution. The constant relation which was observed between the photochemical yields of H+and oxygen in Hill solution, employing different reaction periods, chloroplast concentrations, or Hill solution minus certain components, indicates that these products have a common source, and that illuminated chloroplasts effect a photodecomposition of water.

ISSN:1923-4287    

DOI:10.1139/cjr50c-004

出版商:NRC Research Press    

年代:1950

数据来源: NRC

摘要:

Chloroplast suspensions from the majority of plant species produce titratable acidity in darkness when mixed with ferricyanide – ferric oxalate solution. The rate of production and yield of acid increases between pH 6.0 and 7.5. This oxidation–reduction requires the presence of ferricyanide or ferric oxalate and does not involve enzymes. The nonsugar reducing substances in chloroplast suspensions which participate are water-soluble, and may include ascorbic acid, glutathione, and tannins. By applying a correction for dark acid production, photochemical activity in chloroplast suspensions showing this reaction may be measured by the Holt and French titration method. Boiled leaf sap of Broad Windsor bean produces carbon dioxide rapidly when mixed with ferricyanide – ferric oxalate solution, apparently by oxidative decarboxylation. Crude chloroplast suspensions from this species also exhibit oxygen absorption and dark acid production. Simultaneous measurement of these reactions shows no evidence of quantitative relations. The precipitation of oxalate causes an alkaline drift in pH when crude chloroplast suspensions ofLycopodiumorSedumare mixed with Hill solution in darkness. With crude spinach chloroplast suspensions, interference by dark reactions in photochemical activity measurements is generally negligible.

ISSN:1923-4287    

DOI:10.1139/cjr50c-005

出版商:NRC Research Press    

年代:1950

数据来源: NRC

摘要:

A survey of the major subdivisions of the plant kingdom revealed photochemical activity in chloroplasts and chloroplast fragments isolated from unicellular and filamentous green algae, liverworts, horsetails, herbaceous monocotyledons, and dicotyledons. Active chloroplasts were not obtained from mosses, ferns, gymnosperms, and woody angiosperms. Among 80 species and varieties tested in Hill solution by the titration method, 45 showed photochemical activity quotients above 100, 19 had quotients above 500, and six (millet, flax, spinach, lamb's-quarters, Swiss chard, and lettuce) showed quotients above 1000. Photochemical activity varied greatly within both genera and species. The majority of the chloroplast suspensions produced acid in darkness when mixed with ferricyanide – ferric oxalate solution. Natural inhibitors of photochemical activity were found in the cell sap and cytoplasm of several species.Chloroplast activity quotients in ferricyanide – ferric oxalate and quinone solutions increased with leaf maturation, and declined with senescence. Chloroplasts isolated from very young green leaves of active species were photochemically inactive. The activity of the chloroplasts was relatively insensitive to the supply of essential mineral nutrients and water as well as to growth temperature. Chloroplasts isolated from leaves showing pronounced symptoms of nitrogen, iron, copper, manganese, or magnesium deficiency had low activity quotients, but remained photochemically active until the leaves were about to die. The observed responses to previous illumination and darkness did not support the hypothesis that a labile photosynthetic intermediate, stored in the chloroplasts, is required for oxygen production after isolation.Chloroplast activity was stabilized for weeks by snap-freezing suspensions containing 0.5 Msucrose and storing at or below −40 °C. Lyophilization did not prevent storage deterioration at higher temperatures.

ISSN:1923-4287    

DOI:10.1139/cjr50c-006

出版商:NRC Research Press    

年代:1950

数据来源: NRC

摘要:

The decomposition of soybean, rye, and red clover in naturally infested potato scab soil resulted in marked quantitative and qualitative changes in the microflora, but only soybean reduced disease incidence. Soybean and red clover increased the numbers of bacteria, actinomycetes, and fungi, with rye having a similar effect except on actinomycetes. Tubers invariably supported higher numbers of organisms than corresponding soils. In the soybean soil amino-acid-requiring bacteria were preferentially stimulated, while those with more complex requirements were relatively suppressed. Amino-acid-requiring fungi also were slightly increased and there was a corresponding decrease in those with simple nutrient requirements. A similar effect occurred in the rye soil. When potatoes were grown in the soybean soil, the amino-acid-requiring bacteria were markedly increased on, and correspondingly decreased apart from, the tubers. In contrast, amino-acid-requiring fungi were completely suppressed in the soybean soil, still further increased in the rye soil, and preferentially stimulated only on the tubers in the control soil. The Bacterial Balance Index showed a relationship with degree of infection, the high index in the soybean soil being associated with least scab. This effect was particularly emphasized in soil on the tubers.

ISSN:1923-4287    

DOI:10.1139/cjr50c-007

出版商:NRC Research Press    

年代:1950

数据来源: NRC

摘要:

The compactoid mutants of wheat are, both phenotypically and cytogenetically, the reciprocals of the speltoid mutations. They are determined by excess dosages of the long arm of the C chromosome. This may be through primary polysomy involving the whole C chromosome, or through formation of isochromosomes comprising two long arms of C, or through fragmentation and the presence of excess telokinetic long arms of C. The short arm affects the phenotype slightly in the opposite direction. Other chromosomes present in excess may compensate for lack of C, especially in determining fertility. Most of the compactoid, subcompactoid, and subnormal types are of low fertility but the genetic data obtainable agree with cytological expectation. Very different progeny types and segregation ratios result from compactoid mutants that may be phenotypically and genically similar but different in the structure of their C chromosome constitution. There are three main types of subcompactoids and many subsidiary ones. Primary trisomic subcompactoids usually give only normal, subcompactoid, and compactoid progeny while a secondary type gives normals, subnormals, het speltoids, subcompactoids, and compactoids as regular segregates, besides other abnormal offspring. The data have significance for general problems of polyploid cytogenetics and the systematics of polyploid cereals.

ISSN:1923-4287    

DOI:10.1139/cjr50c-008

出版商:NRC Research Press    

年代:1950

数据来源: NRC