The outer epidermis of Avena and maize coleoptiles is not a unique target for auxin in elongation growth.

A controversy exists as to whether or not the outer epidermis in coleoptiles is a unique target for auxin in elongation growth. The following evidence indicates that the outer epidermis is not the only auxin-responsive cell layer in either Avena sativa L. or Zea mays L. coleoptiles. Coleoptile sections from which the epidermis has been removed by peeling elongate in response to auxin. The magnitude of the response is similar to that of intact sections provided the incubation solution contains both auxin and sucrose. The amount of elongation is independent of the amount of epidermis removed. Sections of oat coleoptiles from which the epidermis has been removed from one side are nearly straight after 22 h in auxin and sucrose, despite extensive growth of the sections. These data indicate that the outer epidermis is not a unique target for auxin in elongation growth, at least in Avena and maize coleoptiles.