, Volume 43, Issue 3-4, pp 249-258

Fine structure of antheridia and oogonia of Phytophthora macrospora, the downy mildew fungus of rice plants

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Abstract

In the present paper fine structure of antheridium and oogonium ofPhytophthora macrospora (Sacc.)S. Ito etI. Tanaka, the downy mildew fungus of rice plants was discussed.

Before the fertilization some nuclei and a large number of mitochondria were scattered in the cytoplasm of the antheridium. Many lipid granules were observed in the peripheral region, but vacuoles did not appear at this stage of antheridium. Many mitochondria were associated in the neighborhood of the fertilization pore. The wall at the pore was very thin, but the wall surrounding the pore was slightly swollen towards the inside.

In the oogonium, many nuclei, mitochondria and cytoplasmic matrix were observed at the peripheral part. A large number of lipid granules was found in the oogonium, but they were more numerous in the peripheral region. The vacuoles developed as the oogonium matured. They were enveloped by tonoplast and contained vacuolar matrix. Many electron dense granules were in contact with the tonoplast or free in the vacuoles, and they were larger in the central part. As stated above, wall at the fertilization pore was thin. However, the oogonial wall surrounding the pore swelled protruding into the oogonium. An electron-dense layer was recognized between the antheridial and oogonial wall, and the walls of both the organs were closely in contact with each other.

Contribution No. 252.