The dose‐response curves for IAA induced elongation growth and acidification of the incubation medium of Zea mays coleoptile segments

The initial dose‐response curves for auxin‐induced elongation growth of Zea mays L. coleoptile segments and simultaneously measured changes of pH of the incubation medium were studied. It was found that these curves are bell‐shaped on all occasions and that at all IAA concentrations studied acidification of the incubation medium took place. The optimum response for IAA‐induced elongation growth and acidification of the incubation medium was 10−5 and 10−4M IAA, respectively. The regression curves and correlation coefficients between magnitude of the growth response and acidification of the incubation medium indicated a close relationship between these sets of data over a wide range of IAA concentrations.