The Development Of The Surface Endosperm Cells In Barley

During the barley (Hordeum distichum L.) endosperm development, the dynamic accumulation of the starch and the changes of cell active were observed by using I2-KI and TTC dyes, and the development of aleurone lay and endosperm transfer cells were studied by using resin embedding and cutting section, which combined optical microscopy with electron microscopy. The main results were shown as follows:(1) The growth of the barley caryopsis and change of respiratory rate: At the primary stage, caryopsis water content was high, and decreased gradually during the rice grain filling. Fresh weight and dry weight of caryopsis increased quickly at the beginning, while it became slow at later period. Respiratory rate decreased following with the water content in the caryopsis. The endosperm cell was activated at the primary stage and then was died at later period because of the accumulation of starch gains. The surface endosperm cells in barley maintained higher respiratory activity in a longer time. In the mature seed, only aleurone lay cells and embryo maintained respiratory activity(2) The development process of the surface endosperm cells in barley was divided into five stages according to the development characteristics: generation stage(3～4 DAP), proliferative stage(5～7 DAP), differentiation stage(8～17 DAP), function stage(15～25 DAP), maturation stage of aleurone lay cells and decline stage of endosperm transfer cells(26～33 DAP). The initial surface endosperm cell was formed in the generation stage between 3 and 4 DAP . Then the initial surface endosperm cell was proliferated in manner of periclinal division until the megaspore was full of endosperm cells on 7 DAP. At the differentiation stage, aleurone lay and endosperm transfer cells were formed, which then went on karyokinesis. The aleurone lay cells were mostly 3-layers and mitotic divisions ceased on 17 DAP. And the transfer cell zone had developed, there appeared 40～45 rows of cells in width and 2～5 layers of cells in depth. Then these two kinds of cells went into the function stage, in which walls ingrowths were found distinctly in these cells. Between 26 and 33 DAP, aleurone lay cells became mature. The mature aleurone lay cells which had thicken cell wall and large nucleolus were full of aleurone grain and spherosome.The structure of walls ingrowths in endosperm transfer cells became constricted and distorted. Nucleolus and cytoplasm of endosperm transfer cells were disaggregated. The shrunk walls ingrowths of endosperm transfer cells merged into the disaggregated cell wall finally. (3) The aleurone layer was transformed by endosperm surface layer cells whichabsorbed and assembled mineral, lipoid, protein and some other material. Aleurone layer cells could absorb nutrients and transport them to endosperm.(4) There were notable positional effects in the formation of Barley endosperm transfer cells. They only distributed in the endosperm nearby the"pool".