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Studies upon the copper fungicides
Author(s) -
Wain R. L.,
Wilkinson E. H.
Publication year - 1943
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.1744-7348.1943.tb06719.x
Subject(s) - copper , spore , bordeaux mixture , dissolution , alkalinity , fungicide , hard water , sterilization (economics) , nutrient , botany , horticulture , biology , nuclear chemistry , chemistry , ecology , organic chemistry , monetary economics , economics , foreign exchange market , foreign exchange
The soluble copper in freshly prepared 4:4:50 Bordeaux mixture was of the order of 7 p.p.m. but on standing in absence of air this fell to 0.7 p.p.m. after 10 days. The dried deposit on glass plates yielded about 0.5 p.p.m. of copper to water. With increasing alkalinity, the soluble copper in freshly prepared Burgundy mixtures decreased to a minimum of about 3 p.p.m. and then rose again. This effect was not observed using dried deposits which yielded consistently less copper to water. The amounts of copper dissolved by water from dried 4:4:50 Bordeaux deposit on runner bean leaves were slightly greater than from the same deposit on glass plates. The results cannot be taken as positive evidence that leaf excretions are involved in the liberation of soluble copper since detached leaves were used and the influence of bacteria could not be eliminated. Suspensions of Neurospora sitophila spores and the nitrates therefrom dissolved copper from dried 4:4:50 Bordeaux deposit in excess of the amount dissolved by water, though these quantities, as well as the amounts of soluble solids in spore filtrates, were appreciably less than were found by other workers in a similar investigation. Steam sterilization of spore filtrates had little effect on their capacity to dissolve copper from dried 4:4:50 Bordeaux. The temperature at which spores were suspended in water was a factor, though the substances capable of dissolving copper were rapidly yielded to water. The nutrient agar on which the fungus was grown influenced the amount of soluble solids in the spore filtrate and the capacity of these nitrates to dissolve copper from dried Bordeaux deposit. Study of the solvent properties of solutions of pure chemical substances of many types showed that copper could only dissolve from dried 4:4:50 Bordeaux deposit by a mechanism involving complex formation. Active substances included amino‐, hydroxy‐, and certain dicarboxylic acids and their salts, all possible constituents of spore exudate. The results obtained with carbohydrates indicated that such substances are not involved in the liberation of soluble copper from this fungicide. A hypothesis on the mechanism of the fungicidal action of copper, based on the results obtained, is presented. This assumes that copper dissolves from the deposit under the influence of excretions from the fungus spore and that the cupri‐complexes produced are the means by which soluble copper is transported to the spore wall. Dissociation of these complexes then make it possible for the active toxicant to be removed by the spore, thus enabling any reversible reactions involved to continue.