Some Effects of Ethylene on the Metabolism of Plants

Ethylene was found to be very effective in producing changes in the general processes of plant metabolism. 2. Chemical analyses showed that ethylene caused the simple soluble substances to increase at the expense of the higher soluble and insoluble forms. a) The hot alcohol-ether soluble substances (sugars, amino acids, amids, polypeptides, lipoids, etc.) increased by 8-9 per cent, while the insoluble substances (proteins, starch, cellulose, ligno-celluloses, etc.) were correspondingly diminished. The water content of the ethylene treated and control tissues was the same. b) The lower soluble sugars (by direct reduction) were about II per cent more and the higher soluble sugars (by reduction after hydrolysis) about 3 per cent less. The reducing power of the alcohol-ether insoluble residue, after hydrolysis, was decidedly less for the ethylene treated tissue; also, the cellulose content was diminished by about 3 per cent. c) Amino acid plus amids were more, and the polypeptides apparently less in the ethylene treated tissue. The protein content also was about 3 per cent less. d) Fats were much less abundant in the treated tissue. The free fatty acid value was unchanged. 3. The acidity of the ethylene treated tissue was not found to be changed. 4. Ethylene caused an increase of osmotic pressure, as measured both by the freezing point and plasmolytic methods. 5. The permeability was not sharply affected by ethylene, although it was somewhat increased. 6. Ethylene affected respiration, retarding both the CO2 production and the O2 absorption, but the respiratory ratio remained practically the same. An exception to the preceding statement was found in the case of the shortest exposure period (3 hours), in which there occurred, apparently, an excessive production of CO2, thereby increasing the ratio.