34 Effect of Copper Compounds 



Trabut (1895) found that on treating smutty wheat with a 2% 

 solution of copper sulphate he obtained a mass of flocculent white 

 mycelium, whose surface was soon covered with aerial branches bearing 

 pale rose-coloured spores, and he gave the provisional name of Penicilliimi 

 cwpricum to the species. On preparing nutritive solutions by steeping 

 a handful of wheat in water for 24 hours, and then adding various 

 amounts of copper sulphate to them, Penicillium was found to vegetate 

 quite well until the amount of copper sulphate reached 9^ grams in 

 100 cc, after which the seedings with spores did not develope at all. De 

 Seynes tested this Penicillium more exhaustively with different culture 

 media under various conditions and decided that Trabut was right in only 

 assigning the name P. cupricum provisionally, as the mould reverts to 

 the form P. glaucum when seeded in a natural medium, indicating that 

 P. cupricum has not an autonomous existence, but is P. glaucum which 

 modifies the colour of its conidia under the influence of copper sulphate, 

 in the same way that it often modifies them in other media. It is 

 noticeable that the mycelium arising from the germination of conidia of 

 P. cupricum in a normal medium has a very poor capacity for producing 

 reproductive organs, but this diminished activity is attributed not to a 

 special deleterious action of the copper sulphate but to the impulse given 

 to the vegetative functions, at the expense of the reproductive, when the 

 spores are seeded in a richer medium than the solutions of copper 

 sulphate which serve as the soil for P. cupricum. 



Ono found that Aspergillus and Penicillium are retarded in growth 

 in the higher concentrations of copper sulphate, but that they are 

 stimulated by weaker strengths. The range of stimulating concentra- 

 tions is given as from -0015 7,, — "012 7o, the biggest crop being obtained 

 with both moulds in the strongest of these solutions. Hattori gives 

 the optimum as being considerably lower for the two fungi mentioned, 

 Penicillium being at its best in a solution of -008 °/^ and Aspergillus in 

 •004 7„. A. Richter (1901) opposes this absolutely so far as Aspergillus 

 niger is concerned. In his experiments copper appears invariably as a 

 depressant, all concentrations from 1/150 to 1/150,000,000 giving growth 

 below the normal, no stimulative action ever being observed. Zinc 

 however proved to be a definite stimulant and in a mixture of copper 

 and zinc salts in appropriate concentrations the toxic effect of the 

 copper was completely paralysed by the stimulating action of the zinc, 

 1/200,000 zinc salt paralysing or overcoming the copper salt at 1/1125 



Ono states that the optimal quantity of such poisons as copper salts 

 is lower for algae than for fungi, copper failing to stimulate algae at 



