studies With C^i-labeled Ethylene 769 



thirds or more can be removed by oven-drying or other techniques 

 and when introduced through the roots it is partially lost via the 



foliage. 



The fixed ethylene apparently does not enter readily into the 

 normal metabolic pathways that result in respiration to carbon di- 

 oxide. More ethylene is fixed by actively growing older plants but 

 not necessarily by older leaves. 



Translocation of ethylene-C^^ or its metabolites was demonstrated 

 by its movement from treated roots or leaves to other parts of the 

 plant. When applied to roots, the highest concentration of radio- 

 activity was found in the terminal meristem. The cotyledons of cot- 

 ton plants in the two true leaf stage contained more radioactive 

 metabolites than the true leaves. When applied to a single leaf, move- 

 ment of radioactivity occurred to nontreatd leaves where it accu- 

 mulated in higher amounts than in the treated leaf. Intact leaves ab- 

 sorbed and fixed larger amounts of ethylene-C^^ than detached leaves. 

 Although more fixation occurred in the dark, more metabolites were 

 translocated under conditions permitting photosynthesis and trans- 

 piration. 



The aqueous extracts from both cotton and Coleus plants con- 

 tained at least two major radioactive metabolites with acidic prop- 

 erties since they were absorbed by and could not be eluted from anion 

 exchangers with electronegative reagents. The major radioactive frac- 

 tion from both sources eluted from the exchange column as the sec- 

 ond peak in the elution sequence. After exposure to radioactive ethyl- 

 ene, as many as seven and nine metabolites were detected by radio- 

 chromatographing the water-soluble fraction of cotton and Coleus, 

 respectively. This suggests either the reactivity of ethylene towards 

 certain native plant materials or the entrance of the ethylene mole- 

 cule into some major metabolic pathway. At present the former pos- 

 sibility seems more logical. Although the amount of radioactivity in- 

 corporated from "aged" ethylene-C^^ compares favorably to the quan- 

 tities of Ci^ from carbon dioxide fixed in the dark by tobacco (18) 

 and by barley in the light (2), the distribution and proportion of the 

 metabolites contained in the various soluble fractions of cotton sug- 

 gest that the C^^ was not incorporated as carbon dioxide. Fixation 

 atypical of carbon dioxide is also indicated by higher radioactivity 

 in the cell wall constituents but lower amounts in the soluble com- 

 pounds than would be expected in 15 hrs. It is highly probable 

 that ethylene is translocated both as the gas and in the form of water- 

 soluble metabolites. 



The major water-soluble metabolites in addition to being strongly 

 electronegative possessed a phosphate ester moiety as indicated by the 



