Failure of colchicine or cytochalasin to inhibit protein secretion by plant cells.

The gibberellic-acid-mediated secretion of α-amylase by aleurone cells of barley and the transport of hydroxyproline-rich cell-wall glycoproteins from the cytoplasm to the wall in phloem-parenchyma cells of carrot roots are not inhibited by either colchicine (1 mM) or cytochalasin (10 μg/ml). The data suggest the absence of a unitary mechanism of protein secretion.