A Rapid Extraction Method for Free Auxin and Its Application in Geotropic Reactions of Bean Seedlings and Sugar-Cane Nodes

Abstract

A method involving extraction with ether for 2 periods of 11/2. hr. was employed for the extraction of free auxin of fresh sugarcane material. This method was adopted because it was found that in the course of ether extraction there is, during the first 1/2 hr., a gush of auxin. This gush was shown to be principally free auxin by using as a test the unilateral distribution of auxin in geotropically stimulated hypocotyls of bean seedlings. Extraction methods involving heat failed because substances which are antagonistic to auxin in the Avena test were found to be released as a result of heating. These inhibitory substances could not be separated from the auxin by simple means. When the free auxin content of horizontal stems of sugar cane is compared with stems in the vertical position, after a few days in the horizontal position the auxin conc. in the meristematic region of the node increases 100% or more. The unilateral distribution of free auxin, so striking in horizontal bean seedlings, is absent in sugar cane. In further contrast to bean seedlings, no growth response to applied auxin[long dash]other than promotion of root growth and bud inhibition[long dash]was found in sugar cane.