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The Action of Toxic Agents Used in the Eradication of Noxious Plants 1
Author(s) -
Harvey R. B.
Publication year - 1931
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj1931.00021962002300060007x
Subject(s) - citation , action (physics) , library science , horticulture , operations research , computer science , mathematics , biology , physics , quantum mechanics
The substances now used for killing noxious weeds and shrubs may be classified on tl~e basis of their type of toxic action as follows: First, substances which by their osmotic action plasmolyze cells and prevent~ plants which are treated with them from obtaining water. An example of such substances is common salt. A second class includes those substances, such ~as hydrocarbons, which by their physical action dissolve or dilute protoplasmic constituents and disorganize the cell by changing its permeability and other physical properties. A third type includes the protoplasmic poisons which stop the action of enzymes, coagulate protein, or combine with other constituents of the protoplasm. Examples of this class are mercuric chloride, cyanides, copper salts, ferrous sulfate, etc. Recent work of the author indicates that this is a type of action exhibited by certain substances which react with the respiratory pigments of plants and interfere with the oxidation-reduction balance in cells. An example of this class ’is sulfur dioxide, which causes the reduction of respiratory pigments so that they can no longer function. Other agents of this type will be discussed later. All of these types may be shown by a substance, the main action being that which comes to expression at the lowest concentrations. For instance, mercuric chloride has an osmotic action, but this does not come into effect generally because the effect of the mercuric ion as a coagulant of proteins occurs at much lower concentrations. To use the osmotic action for killing plants requires that the concentration of the solution shall be rather high, at least higher than the osmotic concentration of the cells of the plant to be killed. The usual range of osmotic pressure in plants is from .~ to 2o atmospheres, but osmotic concentrations of some halophytes may be as high as ~6~ atmospheres. Dry seeds may be able to imbibe water against a force of nearly ~,ooo atmospheres of osmotic pressure. Large quantities of the plasmolyzing agent are required to kill, and to be useful for an eradicant the substance must be very inexpensive. The use of pure saturated hydrocarbons, gasoline, or oils to eliminate plant pests is dependent upon .penetration and conduction