Change in the rate of organelle movement during progression of the cell cycle inAdiantum protonemata

Summary The rate of organelle movement during progression of the cell cycle in single-celled protonemata of the fernAdiantum capillus-veneris is determined microscopically with a time-lapse video system. Under red light organelle movement is very slow (1.8 m/min) in early G₁ in the apical 100-m region. The rate of organelle movement becomes higher in proportion to distance from the nuclear region, reaching a plateau in the neighborhood of 300 m from the tip. Organelle movement during the progression of G₁ and S phases in the dark does not show a significant difference from that in early G₁ under red light. In M phase, however, organelle movement in the nuclear region slows down a few minutes after nucleolar disappearance and then stops until the beginning of cell plate formation. Organelle movement in the basal region of the protonema slows down, but does not stop, shortly after movement in the nuclear region has ceased. This indicates that a message is sent from the nuclear region to the basal region.