摘要:

The method of Lowry and Lopez using ascorbic acid as the reducing agent with the Fiske–Subbarow reagents at pH 4.0 is proposed for the estimation of phosphate in plant extracts. The method has been reinvestigated with respect to its adaptation to the Coleman Universal spectrophotometer, Model 14, to suitability of wave length, pH range, reagent concentration, rate of reaction, color stability, and the effect of silicate. The experiments, in general, confirm those of Lowry and Lopez. A wave length of 650 mμ has been employed. No blue color is formed in the reagent blank between a pH of 3.1 and 4.2; accordingly a pH of 4.0, maintained by a sodium acetate – acetic acid buffer, has been used. A concentration of 0.25% ammonium molybdate and 0.1% ascorbic acid has been shown to be optimum for maximum color development in concentrations of phosphate up to about 25 μgm. P in the final volume. The reduction of phosphomolybdic acid is complete in about five minutes, and the method is characterized by a high degree of color stability. Silicate interferes with the reaction. Where the plant has a liberal silicate economy the cell wall material, with which the silicon is associated, must be removed from the extract. The method has been applied to the estimation of phosphate liberated from organic combination by hydrolysis for specified times in 1 Nhydrochloric acid. Total phosphate is estimated by wet ashing with 60% perchloric acid. Recovery tests of known amounts of inorganic phosphate and glucose-1-phosphate added to wheat leaf and seedling extracts give an absolute error within 2%, which is considered permissible. A balance sheet of phosphate fractions in the supernatant, residue, and whole juice of wheat leaves is discussed.

ISSN:1923-4287    

DOI:10.1139/cjr48c-030

出版商:NRC Research Press    

年代:1948

数据来源: NRC

摘要:

Bacteria and fungi, each cultured on appropriate media at 25 °C., were found to constitute the major groups of organisms in five brands of commercial flour. Numbers of these organisms showed the same trend in relation to brands and the difference between brands was found to be significant. In addition, these brands harbored mesophilic acid-producing bacteria, thermophilic flat-sour spores, anaerobic thermophilic spores, spores of rope-producing bacteria, and yeasts. Numbers of organisms in the latter groups did not show a consistent relationship to brands. The usual method for determining spores of rope-producing bacteria proved to be inadequate for obtaining counts of spores of species known to produce rope in bread. Replication of sampling and careful laboratory procedures were found to be necessary for obtaining reliable estimates of any population in flour.

ISSN:1923-4287    

DOI:10.1139/cjr48c-031

出版商:NRC Research Press    

年代:1948

数据来源: NRC

摘要:

In the examination of agricultural seeds for the presence of seed-borne fungi, five species ofSordariahave been isolated. Three species,S.fimicola(Rob.) Ces. & De Not. isolated from a wide variety of seeds,S.humana(Fuckel) Winter isolated from corn, andS.setosaWinter isolated from beets, are common coprophilous fungi. Two species,S.inaequalisCain isolated from a variety of seeds, andS.curvisporaCain from carrot and celery seed are described for the first time. The fungi do not appear to be of any pathological significance.

ISSN:1923-4287    

DOI:10.1139/cjr48c-032

出版商:NRC Research Press    

年代:1948

数据来源: NRC

摘要:

The Cobb scale and the modified Cobb (U.S.D.A.) scale were devised for estimating, by means of diagrams, the proportion of the area of a leaf or stem occupied by rust pustules. Existing diagrams illustrating these scales are inadequate in being arranged in intervals that are too large and irregular, and in not depicting a sufficient range of pustule sizes. New diagrams are presented using smaller regular intervals of rust intensity and a greater range of pustule sizes, thus providing a basis for more objective and accurate determinations.

ISSN:1923-4287    

DOI:10.1139/cjr48c-033

出版商:NRC Research Press    

年代:1948

数据来源: NRC