Studies With C^i-labded Ethylene llS 



15. Herrero, F. A., and Hall, W. C. Preliminary results on absorption and metab- 

 olism of ethylene-C" in plants. Proc. 56th Assoc. So. Agr. Workers. 1959: 

 224,225. 1959. 



1(3 ^ and Hall, W. C. I. General effects of ethylene on enzyme systems in 



the cotton leaf. (In preparation.) 



17. , and Hall, W. C. II. Effects of ethylene and ethylene derivatives on 



plant mitochondria and some other enzyme systems. (In preparation.) 



18. Kunitake, G., Stitt, C., and Saltman, P. Dark fixation of CO, by tobacco leaves. 

 Plant Physiol. 34: 123-127. 1959. 



19. Pratt, H. K. Direct chemical proof of ethylene production by detached leaves. 

 Plant Physiol. 29: 16-18. 1954. 



20. Ulrich, R. Postharvest physiology of fruits. Ann. Rev. Plant Physiol. 9: 385- 

 416. 1958. 



21. Young, R. E., Pratt, H. K., and Biale, J. B. Manometric determination of low 

 concentrations of ethylene with particular reference to plant material. Anal. 

 Chem. 24: 551-555. 1952. 



DISCUSSION 



Dr. Thimann: As a footnote to Dr. Hall's studies of what happens 

 to ethylene in the plant, I would like to mention some work we have 

 been doing for the last three years on the conditions for the formation 

 of ethylene. This work was carried out in collaboration with Dr. Stan- 

 ley Burg, with the valuable assistance for instrumentation of Dr. Jan 

 Stolwijk who joined us from Holland. I would like also to ac- 

 knowledge the continued advice and criticism of Dr. Bruce Stowe. The 

 first part of the work was largely devoted to improving the methods 

 for determining ethylene, which are very insensitive. Experiments 

 which require having three or four whole apples in a container for 

 several hours are very unsatisfactory for the study of biogenesis, but 

 fortunately Burg and Stolwijk were able to overcome this and, by 

 skillful adaptation of gas chromatographic methods, were able to 

 determine amounts of ethylene only about 1/ 1,000th of that required 

 with the existing procedure of absorbing first in mercury perchlorate 

 and then releasing and measuring the gas volume. I will mention only 

 three of the points which have become clear from this study. The first 

 is the very close relationship between the production of ethylene in 

 plugs or slices of apple, and their respiration. It is possible with these 

 small pieces of tissue to follow in parallel their oxygen consumption 

 and their ethylene production, as a function of oxygen tension. The 

 production of ethylene and oxygen consumption both have pOo^" at 

 between 1.5 and 2 per cent oxygen. Further, numerous respiration in- 

 hibitors all inhibit production of ethylene. Dinitrophenol, iodoacetate, 

 fluoride, fluoroacetate, or, a little less satisfactorily, arsenite, all show 

 the same thing: namely, that the influence on oxygen consumption is 

 paralleled extremely closely by an influence on ethylene production 

 and the level of the inhibitor which just causes a threshold effect is 

 exactly the same for the two processes. These data taken together con- 



