Ultrastructure Of Endosperm Development In Plantago Major L.

Ultrastructural features during development of endosperm and endosperm haustorium in Plantago major L. were described by means of transmission electron microscope to offer some information for embryology of Plantaginaceae. The main results are as follows:1. Development of micropylar endosperm haustorium.After fertilization, the primary endosperm nucleus separates into 4 or 8 endosperm cells and 2 or 4 ones at the micropylar end develop into micropylar endosperm haustorium. At the early stage of micropylar endosperm haustorium, the cells with large nucleolus undergo vacuolization to extend their volume. Ultimately 2 or 4 micropylar endosperm haustoriums are formed.At the middle stage of development, tubular haustorium penetrates into integument. Its micropylar wall has a large amount of ingrowths with a lot of mitochondria around and a few branches. Micropylar haustorium with large amount of organelles begins to absorb and transform nutrition meanwhile integument around it is hydrolyzed. The later period of global embryo, integument is hydrolyzed completely resulted in an cavity, while the absorption reaching to the top. The micropylar haustorium degenerates gradually from the stage of heart-embryo.2.Development of chalazal endosperm haustorium. The chalazal chamber from the first division of primary endosperm nucleus develops into a binucleate haustorium by mitosis without division of cytoplasm. The nucleus is large and nucleus membrane is obvious with large amount of mitochondria,plastids and Golgi bodies around. Abundant rER locate around the other organelles and extend. With increasing in volume of embryo and endosperm proper, chalazal endosperm haustorium expends towards the chalazal end of the ovule while the chalaza surrounding chalazal endosperm haustorium is hydrolyzed gradually. The chalazal endosperm haustorium absorbs and transforms nutrition to engage in forming endosperm proper and storing nutrition. Till the later stage of global embryo, chalazal endosperm haustorium degenerates gradually.3.Development of endosperm proper. The 2 or 4 oblate global cells as opposed to the 2 or 4 conical ones are the original cells of endosperm proper. They increase the number of endosperm proper through anticlinal and periclinal divisions.The endosperm proper surrounding embryo shows spherical shape and stores nutrition in it. Endosperm proper around embryo is hydrolyzed to offer the development of embryo in the period of later global embryo.