Indoleacetic-acid-enhanced chloride uptake into coleoptile cells

Abstract

The enhancement by indoleacetic acid (IAA) of ³⁶Cl^- uptake into Avena coleoptile sections was used to study the effects of a hormone on a membrane-controlled phenomenon. Compared to sections in phosphate buffer only, Cl^- content of the cells increases 15 min after addition of IAA; the promotion is seen only with growth-active auxins and is saturated at 3 μM IAA. The percent enhancement by IAA is the same over a wide range of Cl^- concentrations. The hormone effect is not observed at ice-bath temperature and is not correlated with growth or water movement into the cells. IAA does not influence the movement of Cl^- in the section. While auxin must be present within the tissue in order to maintain the enhancement, there is no relationship between the total amount of auxin and the accelerated Cl^- uptake that results. A polarity in the auxin effect is implied since only apical applications of IAA promote Cl^- uptake.