Fine structure of root nodules of Aeschynomene indica L.

Fine structure of nitrogen-fixing root nodules of Aeschynomene indica L. was investigated by electron microscopy since these nodules arise through intercellular infection and this plant species bears nitrogen-fixing aerial stem nodules. Electron micrographs showed that cells in the bacteroid region were completely packed with spherical bacteroids (o2–3 µm) which were estimated to have multiplied by single binary fission. Bacteroid-filled cells included central large nuclei, several mitochondria and a few plastids within the electron dense cytoplasmic matrix. Cortical cells directly adjacent to the bacterial region were vacuolated and contained rough endoplasmic reticulum, mitochondria and plastids embedding starch granules in their electron dense cytoplasm located at the periphery. Electron micrographs of bacteroids at a high resolution revealed that the membrane surrounding the bacteroid cytoplasm had a double layer structure and that a periplasmic space existed between the layers. Inside the bacteroid, ...