Stem segments of apple microcuttings take up auxin predominantly via the cut surface and not via the epidermal surface

In conventional cuttings, auxin applied to achieve rooting is taken up predominantly via the cut surface and not via the epidermal surface of the stem. Even though in tissue-cultured plants the cuticle is poorly developed and the stomata do not function properly, stem segments of apple microcuttings took up labelled indoleacetic acid also predominantly via the cut surface. Stem segments with an epidermis with gaps caused by excision of the petioles required a lower exogenous concentration of auxin to achieve rooting than segments with an intact epidermis, indicating that the gaps facilitated uptake of auxin from the medium. This was con®rmed in an experiment on uptake of labelled indoleacetic acid. # 2000 Elsevier Science B.V. All rights reserved.