Two Comments on Auxin Transport: The Uptake/Efflux-Mechanism and the Problem of Adaptation

Abstract

A “simple” transport scheme of auxin accumulation in the cytoplasm and auxin “secretion” from each cell consists of two specific molecular transmembrane processes at the plasmalemma: (1) an accumulation of IAA into the cytoplasm driven by a pH gradient and by the electrical membrane potential, and (2) an efflux of IAA through polarly distributed exit carriers. Figure 1 illustrates the mechanism at a cell or at an outside-out plasma membrane vesicle. The exit carriers are inhibited non-competitively by phytotropins and TIBA [3].