Nuclear features in infected roots of Ophrys lutea Cav. (Orchidaceæe)

summary In mycorrhizas of Ophrys lutea Cav., nuclear hypertrophy occurs in infected cells and in some neighbouring uninfected ones. Hypertrophied nuclei are amoeboid in shape and possess numerous nuclear pores. The increase in nuclear volume is associated with an increase of the number of nucleoli from 1 to 2–4. These nucleoli possess well defined granular and fibrillar components and several vacuoles. Nuclear bodies of different sizes are associated with the nucleoli or lie free in the nucleoplasm near the nuclear envelope. Silver impregnation reveals that both the fibrillar component of the nucleolus and the nuclear bodies are argyrophilic. Some nucleolar‐associated bodies do not react with the silver stain. After regressive staining with EDTA, the chromatin, the nucleolar fibrillar component and the nuclear bodies lying free in the nucleoplasm are bleached. The nuclear bodies may be transient accumulations of ribonucleoproteins migrating into the cytoplasm.