Fig. 6

Light micrographs of embryo development of G. elata. a Light micrograph of the zygote after fertilization at 6 DAP. The zygote (arrow) is highly polarized with a chalazally located nucleus. At the micropylar end, one synergid has degenerated (DS), and the other synergid is still persistent (PS). Scale bar 20 μm. b The first cell division of the zygote results in the formation of a two-celled embryo. A few tiny starch grains (arrow) have appeared within the cytoplasm, and several larger starch grains (arrowheads) start to accumulate in the seed coat. Scale bar 20 μm. c An additional transverse division results in the formation of a three-celled embryo. The primary endosperm nucleus (arrow) could be observed within the endosperm cavity, but the endosperm eventually fails to develop. Scale bar 20 μm. d An anticlinal division (arrow) occurring in the terminal cell results in the formation of a four-celled embryo. Scale bar 20 μm. e Light micrograph showing a proembryo with a highly vacuolated suspensor cell (S). Scale bar 30 μm. f Light micrograph showing an early globular embryo with a single-celled suspensor (S). A large number of starch grains (arrows) accumulate within the cells of embryo proper. Scale bar 30 μm. g As the globular embryo approaches maturity, the size of starch grains (arrow) within the embryo proper has become larger and the suspensor finally degenerates. Scale bar 30 μm. h A longitudinal section through a mature seed at 16 DAP. At this stage, the starch grains have disappeared, and a number of small protein bodies (arrow) can be seen within the embryo proper. Although the lipid cannot be preserved in the historesin, the spaces between the protein bodies could be the storage lipid bodies. At maturity, the embryo is enveloped by a shriveled seed coat (arrowhead). Scale bar 30 μm