Summary
The root nodules ofCeanothus integerrimus were perennial, and after one year they were tightly packed masses of small lobes. Each lobe was root-like in organization and was produced by an apical meristem. Nodule branches were pericyclic in origin. The youngest cells at the tip of the lobes were not infected, and the infection progressed towards the tip with the stage of heaviest infection at the widest part of the lobes. In the areas of uninfected and newly infected cells, there were extracellular actinomycetes which sent branches into young cells. As the actinomycete entered the cell, it induced the host cell to deposit cell wall around it, and this cell wall continued to be deposited as the filament grew within the cell. As the infection progressed, the host cell wall that had been deposited around the invading filament was degraded. At the most heavily infected stages little wall material remained. The plant cell plasmalemma preceded the actinomycete as it entered the cell, and it remained as the membrane separating the actinomycete from the host cell cytoplasm.
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Strand, R., Laetsch, W.M. Cell and endophyte structure of the nitrogen-fixing root nodules ofCeanothus integerrimus H.and A.. Protoplasma 93, 179–190 (1977). https://doi.org/10.1007/BF01275652
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DOI: https://doi.org/10.1007/BF01275652