The embryo and endosperm development of watermelon

The development of embryo and endosperm were observed in watermelon (Citrullus lanatus). Embryo development follows the Asterad type and has not obvious suspensor. The first division of zygote is uneven and the ground cell is bigger in size than the apical cell. There are no wall ingrowths on the outer walls of the outer layer embryo cells at micropylar end during the embryo developmental process. After the cotyledons are differentiated,protein and lipid begin to be accumulated but insoluble polysaccharide decreased in cells of cotyledons. Those cells of mature seed contain abundant globular protein bodies,which lots of lipid bodies are around them. Endosperm development follows the nuclear pattern,and endosperm cellularizates at globular embryo. At the stage of early globular embryo,tubular endosperm haustorium is present,which remains coenocytic,then cellularizates. Endosperm proper and haustorium gradually degenerate during the cotyledons growing and disappear in mature seed.