Cytological characterization of multicellular structures in embryogenic microspore cultures of Brassica napus L.

We investigated an embryogenic microspore culture from Brassica napus L. cv. "Topas", 3 days after induction of embryogenesis, using light and electron microscopical techniques. According to our observations, 6 groups of uni- or multicellular structures could be distinguished by differences in size, wall structure, structure and distribution of organelles and the degree of vacuolisation. Only one multicellular group represents real proembryos which are able to form embryos and to regenerate plants. These 6 groups could be detected in living cultures using an inverted microscope. The cell size and the degree of vacuolization are especially useful markers to distinguish the groups. Separate cultivation of the multicellular complexes of the 6 groups in culture plate inserts from the third day of culture proved that only one group contains real proembryos.