Abstract
Electron microscopical studies were carried out to observe cytoplasmic granulation which is observed under a light microscope in the epidermal cells of rice leaves responding resistingly to incompatible races of Pyricularia oryzae Cav. The first obvious changes in the infected epidermal cells of the incompatible combination between race 037 and var. Toride 1 (resistant gene Pi-zt) were invagination of plasma membrane and appearance of lomasome-like structures 24hr after inoculation. Many invaginations in plasma membranes occurred 48hr after inoculation. The invaginated structures of plasma membrane became globular and formed lomasome-like structures. Some globular membrane structures seemed to be detached from the plasma membrane. The outer membranes of lomasome-like structures often disappeared and the vesicles enclosed in the structures were dispersed into the cytoplasm. Degenerated mitochondria and swollen endoplasmic reticula were not observed 36hr after inoculation, but 48hr after inoculation. At 72hr after inoculation, a lot of vesicles of various size (0.1∼1.1μm) were observed in the infected epidermal cells in the inocompatible combination. In the compatible combination between race 037 and var. Koshihikari, such ultrastructural changes as observed in the incompatible combination were rarely observed. The results suggest that the origin of the cytoplasmic granules observed light-microscopically in the infected epidermal cells may not be mitochondria or endoplasmic reticula, but plasma membranes and lomasome-like structures that were originated from plasma membranes. It is indicated that plasma membrane in the epidermal cells of rice is essentially important to initiate the cytoplasmic reaction leading to the specific resistance in the rice blast disease.
