Abstract: 【Objective】The objective of this research was to clarify the relationship between endosperm and its maternal tissue during development process of the sorghum caryopsis. 【Method】Sorghum KS-304 was used as the experimental material with its caryopsis development days precisely recorded and its caryopsis development closely observed. Structural changes of endosperm cells and relation with their maternal tissue were observed through semi-thin sections under light microscopy by applying Spurr resin tissue embedding. The ultrastructure of cells from different tissues and the starch granules wherein in developing and full ripe caryopsis were observed under SEM. The relationships of testa and aleurone layer of full ripe caryopsis were studied through fluorescent microscopy using cryosectioning.【Result】Four stages could be found in caryopsis development, they were formation stage, milky stage, dough stage, and full maturity stage. Accordingly, endosperm development was divided into five stages, i.e. coenocyte stage, cellurization stage, differentiation stage, developmental stage and the final maturation stage, and the first three of which are equal to that of the formation stage of caryopsis; while the last maturation stage corresponds to the last two stages of caryopsis development. It took as long as 15 days for the nucellar epidermis to be fully degraded. The outer peripheral endosperm cells started to accumulate lipid bodies as early as 7 DPA (days after pollination) and, turned into aleurone cells in 11 DAP. Only 1 layer of aleurone cells formed in full ripe caryopsis. Besides commonly seen aleurone granules and globoids, some single amyloplasts were also found on ripe aleurone cells, circa. 3 μm in diameter. Growth and development of endosperm cells also varied according to different locations, amyloplasts in cells surrounding embryo tended to have a slow growth rate and were loosely packed than other areas, making them floury endosperm compared to others’ corneous endosperms when finally matured. Amyloplasts constitution in subaleurone cells were quite composite, in a manner that mingles both aleurone and starchy endosperm cells. Amyloplast formation in starchy endosperm was unique, which has an “occurrence center” during initiation. Starch “grow” inside a tube-like plastid, and when mature, falls apart, leaving the mature amyloplast with an uneven oval shape. Starch/amyloplasts in mesocarp may not be exhausted approaching mature stage, and on the contrary, there seems to be a secondary growth in both quantity and diameter.【Conclusion】 Development of starchy endosperm in sorghum KS-304 showed a similar pattern to the corn. Starch formation of amyloplasts in starchy endosperm followed a unique way and is independent of all other crop spiecies. Cells of mesocarp layer may act as an extra “sink” during later stages in caryopsis development.

Key words: sorghum , endosperm , amyloplast , aleurone , pericarp , testa