114 EFFECTS OF TEMPERATURE ON FUNGI 



at 22.5° C, 30 days; and at 30° C, 17 days. At 22.5° C Neocos- 

 vwspora vasinfecta requires 45 days; at 28.5° C, 30 davs; and at 

 31.5° C, 17 davs. Undoubtedly low temperature is a primary 

 factor in the formation of sporophores by many Thelephoraceae 

 and Polyporaceae, but not all species. This statement is substan- 

 tiated by the occurrence in North Carolina of fresh sporophores 

 of Fomes annosus, Poly poms abietinus, P. sanguineus, Sterenm 

 lobatum, and S. jasciatinn at any time in the interval from Oc- 

 tober to March. 



TEMPERATURE AND ZONATIOX 



Alternation of light and darkness is known to stimulate the pro- 

 duction of daily bands of conidia and hence of zonation in various 

 fungi grown in Petri dishes, as described in Chapter 6. Tempera- 

 ture may also play an important role in zonation. Bisby (1925) 

 made the observation that Fnsariimi discolor sulphureum, which 

 forms zones in response to alternating light and darkness, can be 

 induced to form zones in constant darkness provided that tem- 

 perature is favorable. At a temperature of 16° to 18° C zonation 

 does not occur, even though the cultures are exposed to alternate 

 light and darkness. At 21° C zones can be formed under the 

 stimulus of lisrht, but similar cultures in constant darkness are 

 without zones. At 30° C, however, rings were formed when the 

 cultures were maintained in constant darkness. 



TEMPERATURE COEFFICIENTS 



By temperature coefficient is meant the ratio of the rate of a 

 given physiological process, for example, respiration, at any given 

 temperature to the rate at which this process proceeds at another 

 temperature. Temperature coefficient is frequently represented 

 by the symbol Q ut , meaning that the interval is 10° and that the 

 rate at the given higher temperature is divided by the rate at the 

 temperature 10° lower. Biologists well appreciate the fact that 

 within a range which approximates the minimal and maximal 

 temperature limits for the given organism, the reaction-velocity 

 changes follow van't HoiTs rule. According to this rule, Q u > for 

 the physiological orocess in question should lie between 2 and 3 

 as a minimum. 



