MATURATION AND DORMANCY 



395 



Table 2. Endogenous and Exogenous Oxygen Uptake 

 by Conidia of Fungi* 



Oxygen Uptake f 



Species 

 Neurospora sitophila 

 Monilinia fruclicola 

 Cephalosporium acremonium 

 Myrothecium verrucaria 

 Stemphylium sarcinaejorme 

 Alttrnaria oleracea 

 Aspergillus niger 

 Rhizopus nigricans 



* Drawn from more extensive data of McCallan, Miller, and Weed (173), by 

 permission of the Boyce Thompson Institute for Plant Research, Inc. 

 f In fil/5 hr/mg fresh spores. 

 J Exogenous = uptake with sucrose less endogenous uptake. 



ficult (64, 110, 254). In general, but with some exceptions, germination 

 is more sensitive than spore respiration to both inorganic and organic 

 fungicides (Chapter 14). 



4. MATURATION AND DORMANCY 



It is a common observation that morphologically normal and appar- 

 ently fully developed spores often do not germinate until after a period 

 of time. If this period is relatively short, we speak of maturation; if it 

 is on the contrary a matter of weeks or months, the spore is said to have 

 a dormant stage or resting period. There is as yet no evidence which 

 enables us to say whether these two phenomena are different or the 

 same. 



The failure of newly formed spores to germinate normally is best 

 documented in studies on the uredospores of the rust fungi (73, 200, 

 245, 322), the behavior of which is exemplified by the data of Figure 3. 

 As shown, immature spores have both a slower rate of germination and 

 lower total germination than have mature spores. In addition, imma- 

 ture spores are more sensitive to unfavorable temperatures (57, 73). It 

 appears from most work that immature uredospores can ripen after 

 removal from the sorus (11, 57, 178). The very long period of poor 

 germinability of aeciospores of Gymnosporangium spp. has been note d 

 repeatedly but has not as yet been analyzed (20, 99, 178, 222, 282). 



Both asexual and sexual spores of ascomycetes germinate poorly 



