ENTRY AND EXIT OF INDOLEACETIC ACID IN CORN COLEOPTILES

Abstract

The entry and exit phases of radioactive indoleacetic acid transport were investigated in corn coleoptile sections. Compounds capable of inhibiting auxin transport, particularly p-chloromercuribenzoic acid and N-1-naphthylphthalamic acid, were found to only slightly block auxin entry but severely suppress auxin exit. An oxygen deficiency had little effect on auxin entry but was found to strongly inhibit auxin transport and auxin exit. While indoleacetic acid uptake was proportional to concentration, the exit phase became apparently saturated at concentrations above 10−5 M. Both entry and exit were found to have temperature coefficients of about 2 or more. The low sensitivity of auxin entry to inhibitors, or to oxygen deficiency, and the linearity of entry over a wide concentration range suggest a diffusion component in entry. The strong sensitivity of exit to inhibitors and to oxygen deficiency confirms the involvement of active processes in exit, as expected of a secretion process.