Annals of Botany 39: 363-368, 1975
© 1975 Annals of Botany Company
RESEARCH-ARTICLE |
On the Occurrence of Intracellular Blue-green Algae in Cortical Cells of the Apogeotropic Roots of Macrozamia communis L. Johnson
Botany Department, La Trobe University Bundoora, Victoria, Australia
Received: 22 February 1974
The occurrence of species of the cyanophytes Nostoc and Anabaena in the cortex near the algal zone is reported for apogeotropic roots of Macrozamia communis L. Johnson. Algae were found to occur both intercellularly and intracellularly in cells of the inner and outer cortex. This is the first record of intracellular algae in the cycads and only the second report of this phenomenon in vascular plants. By examination of cells at various stages of invasion by algae, it is interpreted that algal invasion of cortical cells and intercellular spaces is preceded by mucus apparently secreted by algal zone cells of the host, and deposited in intercellular spaces of cortical parenchyma cells nearby. Also algal penetration of cortical cells is preceded by an algal invasion front of finely granular mucal material which bypasses mucus already deposited in intercellular spaces and may either lyse part of the host cell wall or enter through the plasmo-desmata, filling much of the cell cavity. Subsequently, large numbers of the algal symbionts enter the cell and may be enclosed within host wall material. Electron microscopic techniques are now being employed to further clarify these invasion processes.