Studies With C^^-labeled Ethylene 



767 



Table 5. Comparison between fixation of C'-'02 by barley 

 in the light (2) and ethylene-C" fixation by cotton in the dark. 



Dried whole plant 



Ether soluble (I) 



Chlorins (II) 



Phytol (III) 



Carotenoids (IV) 



Other lipids (V) 



Amino acids (VI) 



Acids (VII) 



Sugars (VIII) 



Soluble protein (IX) ... 

 Nonprotein aqueous (X). 



Cellulose (XI) 



Lignins, etc. (XII) 



Barley, 



2.223 g. 

 with 2 X 10" 

 c.p.m. 



Cotton, 

 2.71 g. with 

 10.8 X 106 



c.p.m. 



(per cent) 

 100* 

 11 



* Loss of radioactivity was primarily due to oven-drying of 

 residues for counting purposes. 



the light by barley (2) shows a relatively higher fixation in the cell 

 wall constituents in the case of ethylene (Table 5). 



Amino Acid Fraction 



Chromatography of the amino acid fraction extracted by ethanol 

 (Figure 7) revealed that the radioactivity appeared primarily in one 

 amino acid-like compound. Only a trace amoimt of radioactivity was 

 found in two or three other amino acids as indicated by two dimen- 

 sional chromatography. 



Based on Rf values in several solvents and other tests, the major 

 radioactive compound was originally believed to be tryptophan. Con- 

 siderable attention was given this compound because of its possible 

 significance to indole-3-acetic acid biosynthesis. However, as shown 

 in Table 6, the conclusion that the compound was tryptophan is not 

 fully substantiated as shown by the Rf values in other solvents and 

 the color reactions performed. 



DISCUSSION 



The present experiments were designed primarily to develop basic 

 background information for more detailed experiments on the bio- 

 genesis, metabolism, and physiological functions of ethylene in plants. 

 It was also hoped that the results would serve as a guide to means of 

 increasing the amount of ethylene fixed, and by shortening the fixa- 

 tion period, to facilitate determining the sequence of metabolite 

 formation. 



