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Journal of Biological Sciences
Year: 2008  |  Volume: 8  |  Issue: 7  |  Page No.: 1158 - 1165

Female Gametophyte in Tristichoideae (Podostemaceae): Re-Investigation

S. Sikolia and P. Ochora    

Abstract: A trilocular ovary possesses several anatropous, tenuinucellate and bitegmic ovules on the axile placenta. Selective callose deposition in cell walls and effects of integumentary directional tension (or stress) forces during first meiotic division and natural competition between dyads exists. Micropylar dyad cell degenerates; shift in nutrient supply at megagametogenesis relates to the degeneration of the primary chalazal nucleus. Primary micropylar nucleus undergoes two free nuclear (mitotic) divisions producing four nuclei that alone organize a four-celled female gametophyte consisting of two synergids, a large central egg cell and a polar cell. Filiform apparatus are present in the synergids. Female gametophyte development is of the monosporic category, Apinagia type, form B; syngamy occurs. The cell walls of nucellar cells fails to resist acropetal net tension force of the inner integument, disorganize, break and release naked protoplast in the cavity formed resulting in a structure referred as nucellar plasmodium; role of lytic enzymes is pointed out. Nucellar plasmodium organizes during post-fertilization period in Trisicha trifaria of the Tristichoideae (Podostemaceae).

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