BIOCHEMICAL CHANGES IN SEED DORMANCY 199 



9 A. Poljakoff-Mayber, Enzymologia, 16 (1953) 122. 



10 A. Poljakoff-Mayber and A. M. Mayer, Bull. Research Council Israel, 

 6D (1958) 86. 



11 A. M. Mayer, unpublished results. 



12 A. Poljakoff-Mayber, unpublished results. 



1^ A. Poljakoff-Mayber and M. Ewenari, Physiol. Plantarum, 11 (1958) 84. 

 I'l A. M. Mayer, Physiol. Plantarum, 11 (1958) 75. 

 IS A. M. Mayer, Enzymologia, 20 (1959) 313. 



Note added in proof: Recent work has shown that ascorbic acid oxidase is 

 absent from lettuce seed and ascorbic acid is oxidized by phenolase in a 

 coupled oxidation (Stavy and Mayer, Bull. Research Council Israel, in 

 press, 1961. 



DISCUSSION 



Halvorson Jr. : Your finding of a shift to the tricarboxylic 

 acid cycle during germination is very interesting, as the opposite 

 is the case with bacterial spores. Is the system at this point 

 sensitive to antimycin A, particularly in the presence of thiourea? 

 Is germination stimulated by Krebs cycle intermediates? 



Mayer: I regret to say that we have not tried the sensitivity of 

 antimycin A. As to your second question, there is no clear 

 stimulation of germination by Krebs cycle intermediates. 



Avi-Dor: I wanted to ask you about the increase of activity 

 of the tricarboxylic acid cycle in the mitochondria, noted by you 

 during germination. This increase might be caused by an 

 increase in either the number or the size of the mitochondria, 

 and not by an increase in enzymatic activity. 



Poljakoff-Mayber: We hope to be able to solve this problem 

 with the help of electron microscopy, by observing both the 

 number and the size of mitochondria in different stages of 

 germination. In dried seeds the oxygen uptake per mg nitrogen 

 is very low. It increases during the process of germination from 

 2-5 //1/min/mg nitrogen to several hundreds of jul/mm/mg 

 nitrogen. 



Kohn: I do not understand why light should have any effect 

 on seeds, since they have to be in the ground before they 

 germinate. Could it not be the effect of infrared or heat radia- 



