title: Cell sizes and DNA level in antheridial filaments in relation to the initiation of spermatozoid differentiation in Chara vulgaris L.
abstract: The observations carried out indicate that the exclusion of the S phase initiation from the course of telophase of the last mitotic division in the antheridial filaments of Chara vulgaris, leading to the formation of spermatids is not a simple result of the cell size reduction, gradually accomplished in the course of the successive cell cycles (of S+G2+M type). This critical moment of spermatogenesis is probably induced by the regulators operating at the level of an antheridium. In the conditions of the long (3-5 days) darkness resulting in the cell cycle arrest in antheridial filaments at the early stage of G2 phase there is detected the operation of some additional mechanisms synchronizing spermatogenesis, which enable some retarded antheridial filaments to pass the critical control points and to enter into the process of spermiogenesis insensitive to the lack of the light. The initiation of the differentiation is accomplished either after the cell division induced by the hypothetic inductors of spermiogenesis or -- more rarely -- with omitting mitosis, i.e. in the cells containing 2C DNA.
mesh_terms: D002454:Cell Differentiation; D002455:Cell Division; D004247:DNA / Q000378:metabolism*; D006238:Haploidy; D007399:Interphase; D008297:Male; D008938:Mitosis; D059828:Plant Cells; D010944:Plants / Q000378:metabolism; D013094:Spermatozoa / Q000502:physiology
chemical_list: D004247:DNA