Apparent Antagonistic Effects of Growth-Regulators

1. The effect of (a) 2,4-dichlorophenoxyacetic acid (2,4-D), (b) ethylene, (c) combinations of 2,4-D and ethylene, and (d) gaseous substances from ripening bananas on the rate of ripening of bananas was studied. 2. Some volatile substance, or substances, was given off by ripening bananas that was antagonistic to the ripening effects of 2,4-D on bananas. 3. Synthetically prepared ethylene apparently did not reduce the ripening effects of 2,4-D on bananas. 4. On the contrary, 2,4-D greatly reduced the effectiveness of either chemically prepared or naturally produced ethylene in accelerating ripening of bananas. 5. Application of a nonvolatile form of 2,4-D to bananas did not prevent the evolution of gaseous substances from the fruit which were capable of inducing epinastic responses in tomato plants. The chemical nature of these substances was not determined.