Ultrastructure of Haustorium Development inPuccinia coronata avenae: Some Host Responses

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Abstract
The initial response of host cells to the presence of haustoria in a compatible interaction between Avena sativa and P. coronata avenae was the association of host endoplasmic reticulum with the young haustoria. Subsequently, host Golgi bodies accumulated around the developing haustoria, but no direct association of Golgi bodies with haustoria could be ascertained. There was a close association between the host nuclei and haustoria. The portions of the nuclei that were adjacent to the haustoria were lobed and were often idented by lobes of the haustoria. Tubular complexes occurred in the host cytoplasm between the haustoria and nuclei, but not elsewhere in the invaded host cells. Possible implications of this arrangement of tubules are discussed. Collars were frequently found around the necks of older haustoria. Collars formation was initiated by the deposition of material against the host cell wall at the penetration region and along the haustorial neck. Developing collars were variable in shape; many had long projections radiating into the host cytoplasm. Host endoplasmic reticulum extended between these projections. All collars were continuous with the inner layer of the host cell wall. The collars were largely unaffected by protease, cellulase, or lipid-solvent treatments, but stained heavily with periodic acid-thiocarbohydrazide-silver proteinate. The collars were most likely composed of several types of polysaccharides.