Ethylene and auxin-induced cell growth in relation to auxin transport and metabolism and ethylene production in the semi-aquatic plant, Regnellidium diphyllum.

Cell elongation in the rachis of the semiaquatic fern Regnellidium diphyllum is induced by the addition of ethylene or indoleacetic acid (IAA). Experiments with whole plants or rachis segments have shown that ethylene-induced growth requires the presence of auxin. Ethylene does not cause a modification in either endogenous auxin levels or in the extent of auxin metabolism but auxin transport is reduced. Rates of ethylene production in Regnellidium are not altered by either mechanical excitation or by the addition of auxin. A two-hormone control of cell expansion is proposed in which an initial, auxin-dependent growth event pre-conditions the cells to a further subsequent (or synchronous) ethylene-dependent growth event.