Premium
THE INFLUENCE OF HYDROGEN‐ION CONCENTRATION ON THE GROWTH OF CERTAIN BACTERIAL PLANT PARASITES AND SAPROPHYTES
Author(s) -
BERRIDGE EMILY M.
Publication year - 1924
Publication title -
annals of applied biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.677
H-Index - 80
eISSN - 1744-7348
pISSN - 0003-4746
DOI - 10.1111/j.1744-7348.1924.tb05694.x
Subject(s) - biology , pseudomonas fluorescens , ammonia , botany , vicia faba , bacteria , food science , biochemistry , genetics
Summary and Discussion. It is interesting to see in the foregoing series of experiments that most of the bacterial plant parasites, especially those of the Pseudomonas type, and the non‐parasitic species of the fluorescens type seem to possess three associated characteristics, namely high acid agglutination points and limits of growth, and a capacity to produce alkali rapidly in the presence of nitrogenous food materials. This latter capacity is shown in a less marked degree by other non‐sporing saprophytio organisms such as B. lactis aemgenes . Many sporing species, on the other hand, appear to possess a different physiological constitution, since they produce acid in the earlier stages of growth in sugar‐free peptonized broth, and are characterized by comparatively low agglutination points and growth limits. Tests by Marchal and other observers (14) at a later period of their development have caused these sporing organisms to be regarded as the chief ammonia producers in the soil. The experiments also show that the hydrogen‐ion only begins to act injuriously on the bacteria at concentrations about p H 5.0–4.4. Such hydrogen‐ion concentrations are seldom met with in plant tissues except in the case of acid fruits. The acidity of the cell sap has been determined by several investigators by the hydrogen electrode method; Clevenger(8) found that it varied from p H 4.33 for Buckwheat seedlings to p H 6.40 for Soy bean leaves. The values obtained by Hoagland(ii) for barley tops, by Phillips (17) for Indian Corn and Vicia faba , and by Wagner (21) by means of an indicator method for Sinapis alba, Brassica oleofera, Solanum tuberosum and Sempervivum Hausmanni all lie between p H 4.9 and p H 6.2. The cell sap used in these experiments was generally obtained by pressure of the tissues after grinding with sand; treatment of sections of fresh tissues with methyl red indicates that the acidity of the protoplasm itself is somewhat higher than that of the cell sap, whilst Atkins (1) found that the liquid centrif uged from the tracheae of Acer pseudoplatanus was neutral to litmus. Priestley (18) too remarks with respect to the sap collected from a bleeding vine stem, that, “tested with the usual series of indicators, the p H values of the sap in the vines was practically that of true neutrality.”