Abstract
Auxin is a plant hormone that regulates cell growth and cell differentiation. Auxin moves basipetally from the shoot apex to the basal region along a polar axis of plant. This movement has been believed to be performed through a cell-to-cell transport mediated by specific carriers located in the plasmalemma. Recently, evidence indicating that the plasmalemma of plant cells is one of the targeting sites of auxin has been reported. Exogenously applied antibodies raised against a microsomal auxin-binding protein inhibit cellular responses to auxin, and membrane-impermeable auxin derivatives mimic free auxins in cellular responses. In addition, several enzymic functions found in plasmalemma have been reported to be regulated directly by auxin. These findings indicate that both the auxin receptor and the signaltransduction machinery, in addition to the auxinflux carries, locate in the plasmalemma of plant cells.
