66 RESPIRATION 



TABLE 7 

 Inhibition of Hvphae of Aspergillus oryzae by Cyanide 



Concentration of Cyanide 



STIMULATION OF RESPIRATION 



That it is possible to stimulate or increase the respiratory rate 

 of fungi has been shown by a number of investigators. Pratt and 

 Williams (1939) determined that thiamin and pantothenic acid 

 increase the respiration of certain yeasts. Dammann et al. (1938) 

 showed that Gibberella saitb'mettii, in the presence of thiamin, is 

 able to ferment glucose at an increased rate and that this greater 

 activity 7 is not correlated with increase in mycelial weight. 



Similarly Hawker (1944) demonstrated that thiamin (aneurin) 

 in the amount of 10 y per 100 ml of medium increases the amount 

 of glucose consumed per unit dry weight of mycelium by 

 Melanospora destruens. 



IMPLICATIONS 



Problems related to dormancy of spores and to their germina- 

 tion and early growth appear to be worthy of study by respirom- 

 etry. The Warburg respirometer or some modification of it 

 is also suitable for testing the ability of the selected fungus to 

 utilize different nutrient complexes, for discovering its metabolic 

 rate, and for determining the kind of enzymes that the organism 

 is able to produce. It is possible that the modifying effect of such 

 environmental factors as temperature, pH, and perhaps light might 

 be better understood by respirometrv. In experiments of this 

 sort caution must be exercised in interpreting the results, for the 

 reason that several substrates may be oxidized simultaneously. If 

 a number of oxidative changes are proceeding concurrently and 

 at equal rates, the respiratory ratio cannot be known with any de- 

 gree of accuracy. If the evidence indicates that one substrate is 

 being oxidized to the extent that its respiration predominates, how- 

 ever, the respiratory ratio becomes meaningful. Again, if the 



