Fig. 4.

Scheme of type I and type II B. napus microspore embryogenesis pathways. Type I embryos derive from microspores with their nucleus located close to the microspore cell wall. Type II embryos derive from microspores with a centrally located nucleus. Symmetrical divisions in types I and II structures lead to multicellular ELS formation. In type I embryogenesis, cellulose cell walls are not detected by Calcofluor White staining before day 6 of culture. Globular ELS with the exine remnant at the one pole. Two-domain ELSs released from the exine