| Abstract: | During the early developmental stage of wheat caryopsis the antipodal complex (composed of 20 or more cells) located on the chalazal part of embryo sac gradually turns to degeneration and degradation from its outer part to the innermost, undergoing apparent structural changes of protoplasm. The senescent tissue (antipodals) exports its cell contents continually to support the proliferation and enlargement of the adjacent free-nuclear endosperm and accommodate the dual function of both material transport and nurture supply. The lacking of callose deposition on the boundary wails between antipodals and endosperm is much benefit to the solute transport, but not all cell contents in antipodals undergo thorough degradation until exporting, at least, part of the protoplasm only undergoes limited structural disintegration. The disassembled protoplasmic constituents actively migrate through symplast route in the form of macromolecule. This shows another mode of material transport in feeding endosperm. The occurrence of wide cytoplasmic channel in part of boundary wal ls berween antipodals and endosperm shows a special structural transformation of intercellular connection. Therefore, disassembled nuclear materials, cisternae of endoplasmic reticulum and plastids, mitochondria, etc. could migrate from antipodals into the developing endosperm. It is deduced that this mode of material transport may play an important role in supporting rapid proliferation and enlargement of free-nuclear endosperm in the developing caryopsis. |
