Changes in the activity of transport of newly synthesized RNA from nucleus and nucleolus into cytoplasm during interphase.

In antheridial filaments of Chara vulgaris given a 20 min incubation in 3H-uridine and a 40 min period of postincubation the radioactivity of extranucleolar nucleoplasm was found not altered, the radioactivity of nucleoli decreased by some 50%, and the radioactivity of cytoplasm increased by about 50%, as compared with the values obtained from preparations fixed immediately after labelling. During the periods characterized by an enhanced transcriptional activity of nucleoli, i.e. in middle stages of S and G2 phases, the most intensive RNA migration from nucleolus into the cytoplasm takes place. By the end of interphase the rate of the above process becomes slower, thus leading to accumulation of an intranucleolar pool of rRNA reserved for the sake of daughter cells.