Surface changes inPhytophthora palmivora zoospores following induced differentiation

Abstract

Populations ofPhytophthora palmivora zoospores induced to undergo synchronous differentiation by the addition of pectin showed an ordered sequence of surface changes. Within 10 seconds “blebs” and “microvilli” appeared on the cell and flagellar surfaces. These projections gave the zoospore a highly irregular and even convoluted surface for up to 30 seconds poststimulation. Between 30 and 40 seconds, pits appeared on the surface, which began to assume a smoother texture. Zoospores then rounded up and by 4 minutes had assumed an almost spherical form. At this time the surface became wrinkled as though shrinkage had occurred. Germ tubes could be seen emerging from almost all cells by 40 minutes, and as germ tubes enlarged, the cell surface became smooth again but with a fibrous texture. Many zoospores retained their flagella through to the germling stage.