778 Hall, Miller, and Herrero 



conditions is quite drastically repressed. On removal and exposure 

 to atmospheric conditions there is an increase in respiratory activity 

 and concomitant with this is an increase in ethylene production. Us- 

 ing this response of apples to these conditions of storage, C^^ labeled 

 carbon dioxide was incorporated into the storage atmosphere for sev- 

 eral days. Upon exposure to a normal atmosphere and collection of 

 the evolved ethylene in mercuric perchlorate, it was found that a 

 considerable portion of the fraction was active. I would also like to 

 direct a question to Dr. Hall which is. How do you distinguish ^vhether 

 or not ethylene is metabolized before or after transport? Since only 

 radioactivity is measured the ethylene could be metabolized within 

 the leaf and the labeled material transported as some other metabolite. 



Dr. Hall: At the present time we have not distinguished exactly 

 when the ethylene is metabolized. We do not know whether it's before 

 or after transport. However, it appears that most of the metabolism 

 takes place in the leaf following absorption, and before translocation 

 out of the leaf occurs. Apparently the leaves are the principal organs 

 of metabolism, since much less metabolism occurs after absorption by 

 roots or stems. 



Dr. Thimann: I assure Dr. Teubner I have no objection whatever 

 to intact tissue or anything else that works. It is only that if one needs 

 to feed organic substances to the tissue, the slices are much better. 

 But I would like to ask him if he can give any further details since 

 his experiment suggests that carbon dioxide is converted to ethylene 

 in some way. And so far our efforts to get evidence for this have sig- 

 nally failed. Not only carbon dioxide but many compounds that could 

 be metabolized to give carbon dioxide seem not to transfer any label 

 to ethylene, at least in short-term experiments. It is true that in long- 

 term experiments, labeled sugar gives rise to labeled ethylene but the 

 significance of that is hard to assess. 



Dr. Teubner: I'm not sure how much further these studies have 

 been carried. Complications arose in attempting to examine potential 

 precursors before the apples released their ethylene. We feel sure 

 there is an anaerobic fixation of carbon dioxide and incorporation 

 into organic acid fractions which are then metabolized. The acceler- 

 ated carbon dioxide production upon restoration to a normal atmos- 

 phere is reminiscent of an uncoupling effect. AVe attempted to exam- 

 ine the organic acids, but the quantity of malic acid in apples pre- 

 sented diffic ulties in specific activity determinations. 



