Abstract
Ultrastructures of the fungus-host cell association in crown-rusted oat leaves were investigated by scanning and transmission electron microscopy. Intercellular hyphae growing in infected host tissues partially contacted the outer surfaces of the mesophyll cells. The projection of the cell wall of mesophyll cells and adherent material at the region of contact with the intercellular hyphae and mesophyll cells were seen by transmission electron microscopy, and the unclear border region was observed in this area by scanning electron microscopy. Haustorial mother cells were delimited from intercellular hyphae by septa. The tip of the haustorial mother cell which was globular at the center turned down forming a hook-shaped apex by which the haustorial mother cell and the mesophyll cell surface were connected. A penetration peg originated from the haustorial mother cell near the tip. It seemed that passage of penetration pegs through the host cell walls was accomplished by both enzyme and mechanical forces. The scanning electron micrographs showed that the haustorial body was ellipsoid and a neckband was on the tubular neck near the haustorial body.
