An Autoradiographic Study on the Development of the Female Gametophyte inGinkgo Biloba

Abstract

Abstract Methyl green-pyronin staining and autoradiographic techniques after incorporation of tritiated thymidine, uridine, lysine and tryptophan are used to study the female gametophyte of Ginkgo biloba. In one mature gametophyte four distinct regions are distinguished: 1) the outer region (region a in fig. 1); 2) the region between archegonia (region b in fig. 2); 3) the very limited region (one single cell layer) surrounding each archegonium (region c in fig. 1); 4) the inner region, which makes up the largest part of the gametophyte (region d in fig. 1). The following observations are made: i) cells of region a. These cells are characterized by an uniform cell size but by an heterogeneous nuclear size. Nuclei of celles of region a incorporate tritiated thymidine even after mitotic divisions have ceased. Yet the pattern of incorporation is not that typical of chromosome endore-duplication; it better conforms an extra DNA synthesis of some regions of the genome. Labelling of cytoplasm after tritiated th...