DIFFERENTIAL EXPRESSION OF PARENTAL GENOMES DURING FORMATION OF EMBRYONIC ORGANS IN THE EARLY DEVELOPMENT OF THE FERN MARSILEA-QUADRIFOLIA

This paper reports some experimental results related to the expression of parental genomes during the development of the water fern Marsilea quadrifolia L., a plant with graduated heteroblastic development. We found a non-random segregation of the original chromatids of the pater nal genome, as shown by autoradiography of embryo sections after ferti lization of eggs with [H-3]thymidin-tagged sperm. From the 16-cell sta ge on, label is mainly concentrated in the sectors where apical cells will differentiate, and later in or near the apical areas of the young organs. Similar results had been found previously in Marsilea vestita . We also observed aberrations in primary organ development after fert ilization with sperm treated with actinomycin, ethidium bromide, hydro xyurea, bromodeoxyuridin, or chlorambucil. The growth of the first org ans was quite normal, indicating that they develop under the control o f the maternal genome. The subsequent organs displayed abnormal develo pment, indicating that they are under the control of both parental gen omes.