CHAPTER 16 

 SPORE GERMINATION 



Spore germination, in general, implies a change from an inactive to an 

 actively growing condition. This is accomplished in most fungi b}^ the 

 formation of a germ tube, which continues to elongate and ultimately 

 leads to the formation of the vegetative body of the fungus. In the 

 Phycomycetes the germination of oospores and of some sporangia may 

 take place by the internal formation of zoospores. Certain higher fungi 

 also produce secondary spores externally without the formation of 

 mycelium. 



Among the universal requirements for the germination of spores are 

 (1) suitable temperature, (2) adequate moisture supply, (3) adequate 

 oxygen supply, (4) suitable hydrogen-ion concentration, and (5) viable 

 spores. 



Some of these factors may be measured quantitatively, and for each 

 there is an optimum for germination for a given fungus. The maximum 

 percentage of spore germination in the shortest time will occur when all 

 the influencing factors are at or near the optimum. This is a situation 

 which might seldom occur in nature. Germination will occur or not 

 depending upon the number and relative importance of the favorable 

 factors. 



Clayton (1942) suggests that the differences in nutritional require- 

 ments for germination shown by the various species may be due to dif- 

 ferences in the spore wall and in the composition and quantity of reserve 

 foods. Some spores contain stored food in the form of oil, while others 

 contain glycogen. It is believed that water enters the spore by imbibition 

 or osmosis and activates the enzyme, glycogenase, which hydrolyzes 

 glycogen to sugars. 



Spores which do not germinate after being exposed to the usually 

 favorable conditions for a reasonable length of time are said to have a 

 period of dormancy, which may be broken by the presence of a special 

 set of conditions. Among these are (1) exposure to high or low tempera- 

 ture, (2) the presence of certain nutrients or stimulants in natural prod- 

 ucts, (3) exposure to chemical stimulants, (4) alternate wetting and dry- 

 ing, and (5) aging. These same factors may also influence the percentage 

 of spore germination of many species which do not have a definite dormant 

 period. Dormancy may be due, at least in some cases, to the failure of 



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