770 Hallj Miller, and Herrero 



positive Hanes and Isherwood reaction. It has been reported that 

 certain phosphorylated organic compounds, mainly insecticides, are 

 able to elicit ethylene-like symptoms in cotton, tomato, carnation, and 

 other plants (11, 12, 13). All of these compounds have free or potential 

 ethyl phosphate groups as parts of more complex molecules. It is 

 possible that these ethyl phosphate-containing compounds are metabo- 

 lized by plants to ethylene, or, more logically, ethylene enters into 

 direct combination with one or more of the many fundamental phos- 

 phorylated compounds known to exist in plants. This suggests a re- 

 lationship between ethylene and phosphorylation reactions and a 

 feasible explanation of some of the striking effects of ethylene treat- 

 ment on plants. For example, it would be attractive to propose as 

 suggested in the literature (9) that ethylene functions by uncoupling 

 phosphorylation from oxidation. This, however, is not the case since 

 significant effects of ethylene upon phosphate uptake or on the 

 transfer of phosphate from ATP to glucose could not be demon- 

 strated with cytoplasmic homogenates or with mitochondria (17). 

 Neither was ethylene-C^^ incorporated by mitochondria (17). Other 

 theoretical implications of ethylene upon phosphorylation could be 

 postulated, but any hypothesis based on the available evidence would 

 be largely speculation. 



The observation by Buhler et al. (7) concerning the incorporation 

 of ethylene specifically into succinic and fumaric acids has not been 

 confirmed from the present material under study. Labeled organic 

 acids do exist in the alcohol-soluble fraction. 



In both Coleus and cotton the major portion of the labeled carbon 

 in the ether-soluble fraction was found in association with the caro- 

 tenes. Radioactivity in the xanthophylls suggests turnover from the 

 carotenes by oxidation. Genevois in 1954 (10) expressed the opinion 

 that carotenoids may arise from ethylene. Since some 65 per cent of the 

 ether-soluble radioactivity was present in the carotenoid fraction, it 

 may be assumed that ethylene has reacted with /^-carotene or served 

 as a precursor in its formation. The function of ethylene in inducing 

 chlorosis, coloring, and ripening changes in green organs attaches 

 physiological significance to these observations. A corollary observa- 

 tion is that catalase is inhibited by ethylene (15). The effects of ethyl- 

 ene upon the pigments and catalase, all found in close structural 

 proximity on the chloroplasts, may have more significance than cir- 

 cumstantial evidence and speculation now permits. 



Rapid fixation and a relatively high retention of the radioactivity 

 from ethylene-C^^ by cell wall constituents may prove to be important 

 in explaining cell wall modifications induced by ethylene, including 

 cellular growth, ripening, and abscission. The preliminary results ob- 

 tained to date do not permit any positive conclusions in this regard. 



