The Ultrastructure of Developing and Germinating Chlamydospores of Phytophthora Palmivora

The ultrastructural aspects of the development and germination of chlamydospores of Phytophthora palmivora were studied by electron microscopy. A gradual transition from a cytoplasm containing an abundance of mitochondria, dictyosomes, endoplasmic reticulum, and ribosomes to that consisting of 90% “storage” cytoplasm was observed as chlamydospore initials expanded and deposited secondary walls. The “storage” cytoplasm was made up of vacuoles and lipid inclusions. Secondary walls were extremely thick when chlamydospores developed in papaya juice, but much thinner when these cells developed in V-8 juice. Dictyosome-derived vesicles of two types underlie the plasma membrane during the expansion and secondary wall deposition phases of development. Vesicles were also at sites of secondary wall erosion during preliminary stages of germ tube formation. Germ tubes penetrate the secondary and primary walls during germination.