Research On Starch And Protein Accumulation And Metabolism During The Development Of Seeds In Ginkgo Biloba L.

Ginkgo biloba L., an old extant seed plant in the world, has a significant value for research and exploitation. The episperm, kernel and embryos of Ginkgo seeds were observed using transmission electron microscopy, scanning electron microscopy and light microscopy, to reveal the formation, accumulation of starch, protein and other nutrients in the episperm, endosperm and embryo. The nutrient changes were determined and analyzed during the development process of episperm. The main results are summarized as follows:1. During the growth and development process, the length, width and weight of Ginkgo seeds showed as follows: the seeds grew rapidly from flowering to 64 d after pollination, and then the growth rate tends to slow. The seed is about 3.1 cm long, 2.4 cm wide when it matures. The fresh weights of episperm began to increase rapidly at 50 d after pollination, and the dry weights increased later. The water contents of episperm are higher in earlier stage, and then declined gradually. The starch contents reached to peak value of 1.094% at 50 d after pollination, and then declined gradually till undetectable when harvest. The protein contents of episperm were higher in earlier stage, and then declined sharply during 65-80 d after pollination. There is a decreasing tendency of protein contents throughout the late development stage.2. The amyloids of episperm are surrounded by a network structure in earlier stage. With the increasing of starch granules, the size of plasmid increased and the network structure disappeared gradually. Then the starch formed as a free state in the cytoplasm. The amyloids has a bigger size and increased in number at 30 d after pollination than that of later. During 60-120 d after pollination, the starch granules were in a sparse distribution and the starch number was reduced. At 150 d after pollination, the numbers of starch in episperm decreased and the starch disappeared ultimately.3. The accumulation of nutrient in endosperm can be divided into four distinct phases: 1) Thin wall cells proliferation formed ultimately 30-45 d after pollination. 2) The formation of starch, and small amyloplast was abundant in parenchyma cells during 45-60 d after pollination. 3) The fast-increase accumulation of nutrient with the number of starch increased and proteoplast started to form among them after pollination 60 days. Meanwhile, the starch proliferated by the way of budding or constriction in the middle. The number and volume of starch increased markedly at 90 days after pollination. And protein presents as forms of P1 and P2. 4) The slow-accumulation of nutrient with the starch and protein were mature 120-150 d after pollination. The number and volume of starch and protein were almost kept stable.4. Embryogenesis of Ginkgo experienced the development of proembryo stages, differentiation of young embryo stages and development of upper embryo stages. At the formation of the original embryonic cells, the cells are particularly with large and obvious nuclear, and more mitochondria in the cytoplasm. At the differentiation of embryo stage, the cristaes of mitochondria are fewer in the cytoplasm, and starch grains are appeared. Starch grains and other nutrients are accumulated in the embryo stem cells, but no accumulation in the embryo cells. And embryonic stem cells present in large volume and cell gap, while the embryonic cells were small, closely arranged. After seed harvesting, tissue differentiation, organ formation and the accumulation of nutrients in seeds are continuing, and a large number of starch are forming and accumulating as well.