Ultrastructural Modifications Associated with the Induction of Abscission in Coleus

Abstract

Physiological studies indicate that, in explants of Coleus blumei, treatment with the surfactant UBI-1126 accelerates the rate of abscission in cortical cells of the petiolar abscission zone. Ultrastructural observations show that the surfactant treatment brings about extensive modifications of the plasma membrane, including membrane-filled and inclusion-filled invaginations, disruption of the tonoplast, degeneration of the cytoplasm, dissolution of the middle lamella, and cell-wall disruption. Some of the surfactant effects simulate those noted in ethylene-accelerated abscission in other plants. Results suggest that, as a mild organic detergent, the surfactant causes disruption of membrane systems which may stimulate either release of hydrolytic enzymes or a controlling regulatory mechanism for their synthesis, release, or activation.