Mechanisms of auxin-induced plant cell elongation

Abstract

An alternative to the wall acidification theory of auxin-induced elongation growth is presented. A central effect of auxin is postulated to be cytoplasmic acidification, possibly via an increase in the levels of cytoplasmic Ca2+. Activation of the outwardly directed electrogenic proton pump resulting from acidification would lead to changes in Δψ and transmembrane ion gradients. We argue that these changes, rather than wall acidification, are involved in elongation growth.