On Auxin‐Induced pH Drop and on the Improbability of its Involvement in the Primary Mechanism of Auxin‐Induced Growth Promotion

Publisher Website
Google Scholar
Abstract
When sunflower hypocotyl segments were floated on a solution containing potassium, auxin brought about a pH drop in the medium. The effect was detectable about 2–3 hours after the application of the auxin, and persisted during the 26 hours of the experiment. When ammonium was applied instead of potassium, an auxin‐induced pH drop was also noted in the first hours of the incubation. Afterwards, the pH of the auxin‐treated medium became higher than that of the control solution. It is suggested that the difference in the action of the auxin in the presence of the two cations is related to the contrast between its effects on their absorption.The data are discussed in relation to the recently proposed hypothesis that auxin‐induced growth promotion is a result of an auxin‐induced pH drop in a cell wall compartment. It is concluded that the results do not support the hypothesis.