Behavior in tissue culture of nitrogen-fixing root nodules of Ceanothus integerrimus

Publisher Website
Google Scholar
Abstract
The in vitro growth of N2-fixing root nodules from the dicotyledonous shrub C. integerrimus (Rhamnaceae). Root nodule lobes were removed from cultivated plants, surface sterilized and cultured on agar media containing varied amounts of N. Uninfected cells inside the cultured nodules divide and form a callus which is visible after 7 days of growth. Cells infected by the N2-fixing actinomycete do not divide, but rather degenerate. Host cell cytoplasm disappears and organelles and the plasma membrane are no longer seen under the EM. Endophyte structure also deteriorates. Nucleoid areas within the terminal vesicles become diffuse. Cross walls separating vesicles from the hyphae disappear and cytoplasm of the hyphae withdraws from the actinomycete wall. Ceanothus nodules readily form callus in tissue culture. Callus proliferates from uninfected cortical parenchyma outside the infection zone. The callus is free of living endophyte and is incapable of fixing N2 as measured by acetylene reduction. Nodule tissue growth in vitro is more vigorous on media with high N than on N-deficient media.