Fig. 2

Successive cell divisions and expansion of the cell layer in embryogenesis of G. pectorale. Successive stages of an embryo observed by time-lapse analysis from the anterior-lateral view (Additional file 2). All images are at the same magnification. Scale bars: 5 μm. Note the longitudinal axis of each daughter protoplast, indicated by the positions of apical ends (arrowheads) and chloroplasts (letter c). a Early 8-celled stage. b Late 8-celled stage. c Early 16-celled stage. Rotation of daughter protoplasts is not observed during cell divisions (a–c). d Mid 16-celled stage during partial inversion. The cup-shaped cell layer of the embryo has expanded and the apical ends of outer daughter protoplasts (arrowheads) have separated from one another and moved outwards. e Late 16-celled stage, just prior to hatching. The cell layer has increasingly expanded and rotated slightly to show an almost anterior view