Abstract
The uptake of H3-uridine was investigated in two lines of Chara: a “nitellised” (without cortical cells and sex organs) and a normally corticated. Differences were noted between the activity of both lines in the successive segments from the apex, and independently in the branchlets of the whorls and in the internodes.
In corticated samples, RNA turn-over was followed in antheridia during the last division of spermatogenesis and in oogonia at various stages of development. AMD exposures were found to inhibit RNA synthesis more drastically in “nitellised” than in corticated samples, but much less in oogonia. These findings were correlated with cytological observations, which revealed a higher sensitivity of internodal nuclei in which nucleoli progressively disappear and the nuclear segmentation at the end of amitosis cannot be achieved. Some phenomena described can be related to the occurrence of specific gene amplification processes in Chara cells.
