Fig. 2. Comparison of the effect of knolle and keule on cytokinesis and on the cellularisation in the endosperm. Seeds with embryos at late heart stage originate from heterozygous mutant plants. Homozygous mutant seeds are identified by their embryo phenotype and seeds with a wild-type phenotype from the same silique are used as controls. (A,B) Wild-type reference seed with late heart stage embryo and fully cellularised endosperm around the embryo (A) and in the PEN (B). (C,D) keule mutant seeds contain an embryo with multiple defect in cytokinesis, and multinucleate enlarged cells (C) whereas the endosperm cellularisation is not affected (D). (E,F) knolle produces seeds with embryos defective in cytokinesis (E) and non-cellularised endosperm (F). Embryos of the double mutant knolle/keule are characterised by a complete absence of cytokinesis and are reduced to multinucleated tubes (G). However the defect of cytokinesis in the endosperm is no more pronounced than in knolle (G,H). Scale bars represent 20 µm.