Ultrastructural and autoradiographic studies of non-generative cells in the antheridium of Chara vulgaris. I. Manubria

During the development of an antheridium DNA content in manubria gradually increases to 8C-16C level. 3H-thymidine incorporation into the nuclei of the manubria lasts till the stage of quantitative predominance of the 16 celled antheridial filaments. The nucleus of the manubria is characterized by the low content of the condensed chromatin and the presence of nucleoli with the nucleolonema-like structure the number of which increases from 6-8 to 32-38 along with the increase of DNA content in a nucleus. In the cytoplasm of the manubria there are numerous secretive vesicles filled with fine-granular substance discharged outside plasmalemma, active Golgi apparatus, well-developed rough ER, numerous polysomes, mitochondria with the condensed structure and plastids with granar and inter-granar thylakoids as well as plastoglobules which increase in number and size along with the development of the antheridium. During spermiogenesis the cells are vacuolated, the number of the secretive vesicles decreases whereas the electron density of their content increases, smooth ER appears while rough ER is reduced. The manubria actively incorporate 3H-uridine, 3H-tryptophane and 3H-leucine. The increase of the incorporation activity is gradual in the period of increasing polyploidy of the manubria and rapid during the initiation of the spermatozoid differentiation. It has been suggested that the manubria should play an important role in the process of spermatogenesis and the induction of spermatozoid differentiation.