Fine structure ot the protonema in the moss Ceratodon purpureus and its response to a cytokinin

Abstract

Fine structure of the protonema is described, with a special attention to its differentiation depending on the position of cells in the protanemal filament, as well as in response to a cytokinin treatment. Complexes of micro-filaments with osmiophilic globules represented structures of particular interest. They appeared temporarily, almost exclusively in apical cells. The cytokinin treatment resulted in the apical cells in an increased number of cytokinetic figures and in structural changes indicating increased metabolic activity. In the intercalary cells, changes in response to the cytokinin were much smaller and mostly concerned an augmented development of the thylakoid system in chloroplasts. After a prolonged (5 days) treatment, degeneration symptoms developed in all cells, particularly in nuclei and chloroplasts, whereas the structure of mitochondria was relatively stable. The results are compared with the observations concerning the cytokinin-induced gametophore buds and with the data of biochemical and physiological investigations of the protonema.