Further Evidence of Persistence Of the 2,4-D Stimulus in Cotton

Abstract

The persistence of the 2,4-D stimulus was demonstrated in the vegetative organs of 2 vars. of cotton, Stoneville 2B and Marie Galante. Evidence for this persistence was shown by (a) the period of time during which the plants continued to produce malformed main stem leaves[long dash] up to 6 mos., and (b) the number of malformed leaves produced[long dash]as many as 24. It was found that the number of malformed leaves formed was in excess of the number of leaves or leaf primordia in the terminal bud at the time of treatment, thus eliminating the possibility of an immediate effect not becoming evident for an extended time. That the persistence was not due to continued absorption of 2,4-D by the leaves was also established. Persistence of the stimulus was further demonstrated by extraction of a growth-regulator from treated plants which induced cotton leaf malformations characteristic of 2,4-D. This regulator was extracted 80 days subsequent to the initial application of 2,4-D. Whether the growth-regulator was 2,4-D or a derivative therefrom was not clearly demonstrated. That this substance was not a naturally occurring auxin was established by its stability in alkali and acid solns.