SPORE GERMINATION 369 



present in appreciable quantities in vegetative cells. Since the metabolic 

 activity of a resting spore is at a minimum in contrast with that of actively- 

 growing vegetative cells, the internal responses to the environmental 

 factors may be quite different. 



The variability of the needs of spores of different fungi for germination 

 is adequately illustrated in the literature. Certain general conditions 

 are essential for all spores, while some require a special set of conditions. 

 Water is essential to activate certain enzyme systems, to initiate other 

 internal chemical changes, and to increase the volume of the germinating 

 spore. WTien the temperature is near the optimum, the enzymatic 

 activity and the rate of spore germination are increased. The supply of 

 oxygen must be adequate to meet the demands of the greatly increased 

 rate of respiration. The acidity of the substrate must be favorable. 

 Variability in the period of viability of spores is striking, but longevity 

 is greatly influenced by the environment. Much information is yet to be 

 gained regarding the longevity of spores, particularly of the plant 

 pathogens. 



Certain special conditions are required for germination of some spores. 

 These may act as a stimulant in breaking dormancy or may supply needed 

 nutrients. The effects of other living organisms, or even of the substrate 

 upon which they have grown, are of particular interest, for such associa- 

 tion is the usual condition under which germination occurs in nature 

 One might suppose that the secretions of certain plants would exert a 

 selective action on spore germination and affect the pathogenicity of 

 certain fungi, but evidence on this point is lacking. 



The production of short germ tubes by spores of some species of Ery- 

 siphe in an absolutely dry atmosphere is unusual. If this is to be con- 

 sidered as true germination, it must represent a unique method among 

 fungi. The Erysiphales, however, are excellent examples of fungi whose 

 spores germinate in atmospheres of lower relative humidity than most 

 fungi can endure. 



Under the changing conditions of nature, the period of time during 

 which a factor is active is of utmost importance. Germination is the 

 result of the action of all the influencing factors operating at the same 

 time. Most of these factors vary in intensity or concentration, so that 

 the combined optima of all factors are seldom, if ever, reached at any 

 given time in nature. As a result, an extremely low percentage of the 

 spores formed by a fungus ever germinate, while still fewer give rise to 

 extensive mycelium. 



REFERENCES 



Anderson, P. J., and W. H. Rankin: Endothia canker of chestnut, Cornell Univ. 



Agr. Expt. Sta. Bull. 347, 1914. 

 Bonner, J. T. : A study of the temperature and humidity requirements of Aspergiltus 



niger, Mycologia 40: 728-738, 1948- 



