Cover illustration: The developmental pathway of single cells and few-celled aggregates isolated from embryogenic cell culture of Picea abies can be analysed by time-lapse tracking technique. The latter has shown that somatic embryos develop not directly but from proembryogenic masses which pass through a series of three characteristic stages distinguished by cellular organization and cell number (stages I, II and III) to trandifferentaite to somatic embryos. In Picea abies, the lack of staining of the arabinogalactan protein epitope recognized by the monoclonal antibody JIM13 is an efficient marker for distiniguishing proembryogenic masses from somatic embyros. The image shows JIM13 staining of stage III proembryogenic mass (bottom) transdifferentiationg to two somatic embroys (top). The cell walls of proembyrogenic mass exhibit strong specific immunostaining (yellow to green), while somatic embryos do not react to the antibody (red autoflourescence) (see Filonova et al., pp. 249-264).
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