A NEW STEM-END ROT OF POTATO

1932 ◽  
Vol 7 (5) ◽  
pp. 520-523
Author(s):  
W. R. Foster ◽  
H. S. MacLeod
Keyword(s):  
Field Experiments ◽  
Storage Temperature ◽  
Control Measure ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Effective Control ◽  
New Disease ◽  
Optimum Temperature ◽  
Causal Organism ◽  
Hydrogen Ion Concentration

A new disease of potato, a hard, dry, corky, stem-end rot with a sharply defined margin, is reported from the coastal area of British Columbia. Stem-end hard rot is the name suggested for this disease. A fungus, Phomopsis tuberivora Güssow and Foster, isolated from rot lesions, reproduced typical symptoms of the characteristic stem-end rot. The optimum temperature for the growth of the causal organism is between 20° and 25 °C. The optimum hydrogen ion concentration for the growth is approximately 6.5.Between 38° to 40° F. (3.34 to 4.45 °C.) the usual storage temperature for potatoes, the disease makes little progress. Dipping the diseased potatoes in mercuric chloride, 1:1000, was not an effective control measure. Evidence of field experiments indicates that diseased tubers should not be used for planting purposes.

scholarly journals Studies in the mechanism of enzyme action. I.—Rôle of the reaction of the medium in fixing the optimum temperature of a ferment

1921 ◽  
Vol 92 (642) ◽  
pp. 1-6 ◽  
Keyword(s):  
Enzyme Activity ◽  
Temperature Effect ◽  
Acid Medium ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Optimum Temperature ◽  
Hydrogen Ion Concentration ◽  
Enzyme Action

Previously, it has been shown for the enzyme maltase —enzyme requiring an acid medium in which to act to best advantage—that increase in the acidity or hydrogen ion concentration of the medium in which the enzyme acts, beyond the optimum acidity, leads to a fall of optimum temperature. The mechanism of his temperature of this temperature effect appears clearly to be due to a certain disablement of the enzyme activity, estimated at the optimum temperature point; which decrease of activity is itself a function of the degree of acidity of the medium in excess of that necessary to produce optimum activation. Being in this way a disablement effect, the question arises whether, by adding to the quantity of enzyme in action, the lowering of optimum temperature which takes place can be controlled. To answer that question, the experiments described in the present paper were undertaken. For the investigation, the enzyme used is the maltase of Aspergillus oryzœ , the same preparation being employed as studied by us in two previous communications, a specially active specimen of takadiastase, purified by repeated solution in water and reprecipitation by alcohol.

scholarly journals The influence of the hydrogen concentration upon the optimum temperature of a ferment

1915 ◽  
Vol 88 (605) ◽  
pp. 408-417 ◽  
Keyword(s):  
Experimental Investigation ◽  
Alkaline Medium ◽  
Hydrogen Concentration ◽  
Special Interest ◽  
Ionic Concentration ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Optimum Temperature ◽  
Hydrogen Ion Concentration

The present investigation is an outcome of previous work, resulting in the discovery that the optimum temperature of any ferment, or ferment function, occurring in a given enzymic preparation, is independent of the concentration both of the substrate and of the enzyme, the duration of the substrate and of the action being constant. To follow up this observation it was felt desirable to investigate in a similar way the influence, if any, of the reaction, that is of the hydrogen ion concentration of the medium, on the reaction, that is of the hydrogen ion concentration of the medium, on the optimum temperature of enzyme action: the more so because enzymes, as regards their activity, are known to be extremely sensitive to this factor—some requiring an acid, others a neutral, and others again an alkaline medium in which to act. The question, moreover, is of special interest on account of the fact that Sörensen, in his classical researches on the rôle of the ionic concentration of the medium in activating enzymes, alludes to it, and predicts in regard to it that, when investigated, the optimum temperature will no doubt be found to vary with the hydrogen ion concentration of the medium. That opinion, being of a speculative nature, was not deemed a sufficient answer to the question; its experimental investigation therefore became the more needed. The enzyme chosen was the maltase of Aspergillus oryzæ , the same preparation being used as had already been studied in a former communication, where its optimum temperature, in an action of 16 hours’ duration, and H+ concentration that of the preparation simply dissolved in redistilled water, is shown to be +47º.

EFFECTS OF SOIL ACIDITY ON RHIZOBIA NUMBERS, NODULATION AND NITROGEN FIXATION BY ALFALFA AND RED CLOVER

1977 ◽  
Vol 57 (2) ◽  
pp. 197-203 ◽  
Author(s):  
W. A. RICE ◽  
D. C. PENNEY ◽  
M. NYBORG
Keyword(s):  
Nitrogen Fixation ◽  
Soil Ph ◽  
Soil Acidity ◽  
Field Experiments ◽  
Rhizobium Meliloti ◽  
Acid Soils ◽  
Red Clover ◽  
Ion Concentration ◽  
Hydrogen Ion Concentration ◽  
Greenhouse Experiments

The effects of soil acidity on nitrogen fixation by alfalfa (Medicago sativa L.) and red clover (Trifolium pratense L.) were investigated in field experiments at 28 locations, and in greenhouse experiments using soils from these locations. The pH of the soils (limed and unlimed) varied from 4.5 to 7.2. Rhizobia populations in the soil, nodulation, and relative forage yields (yield without N/yield with N) were measured in both the field and greenhouse experiments. Rhizobium meliloti numbers, nodulation scores, and relative yields of alfalfa decreased sharply as the pH of the soils decreased below 6.0. For soils with pH 6.0 or greater, there was very little effect of pH on any of the above factors for alfalfa. Soil pH in the range studied had no effect on nodulation scores and relative yields of red clover. However, R. trifolii numbers were reduced when the pH of the soil was less than 4.9. These results demonstrate that hydrogen ion concentration is an important factor limiting alfalfa growth on acid soils of Alberta and northeastern British Columbia, but it is less important for red clover. This supports the continued use of measurements of soil pH, as well as plant-available Al and Mn for predicting crop response to lime.

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