Development of Ovule and Embryo Sac in Blotched Tree Peony (Paeonia rockii)

Abstract

This paper dealt with the ovule ontogenesis and development, the megasporogenesis and the embryo sac development in Paeonia rockii cvs. The ovule, originated from the tri-zonate primordium, was anatropous, bitegmic and crassinucellate. And the nucellus consisted of different cytohistological zones and differentiated by a particular way in which the derivative cells from both parietal and sporogeneous cells were contributed to the nucellar tissue. During the megasporogenesis and before the 4-nuclear embryo sac, the megasporocytes successively entered meiosis or commenced to degenerate. Generally a linear tetrad formed after meiosis and the chalazal megaspore was functional and developed into embryo sac by Polygonum type. Multicelled archesporium and multiple megasporocytes in an ovule resulted in 1-3 embryo sacs, which developed to mature within several days after anthesis. Belated mature of embryo sacs supplies a device to guarantee the cross-pollination. The characteristics about ovule and embryo sac of peonies were more primitive and imply the primitive of Paeoniaceae in phylogeny