There are three types of endosperm, viz., nuclear, cellular and helobial.
(i) Nuclear endosperm:
1. Nuclear endosperm is the most common type of endosperm.
2. During the formation of nuclear endosperm, the primary endosperm nucleus (PEN) undergoes free nuclear division forming a large number of triploid nuclei which remain freely suspended in the common cytoplasm of central cell.
3. A central vacuole pushes the nuclei towards periphery.
4. Later on wall formation takes place around these nuclei to form a cellular mass.
5. It is seen in plants like maize, sunflower, wheat, coconut, etc.
(ii) Cellular endosperm:
1. In this type of endosperm, the triploid primary endosperm nucleus undergoes nuclear divisions followed by cytokinesis.
2. Owing to this, the development of endosperm occurs in cellular form.
3. It is less common and seen in dicot plants like Datura, Petunia, Balsam, Adoxa.
(iii) Helobial endosperm:
1. In helobial type of endosperm, the first division of the primary endosperm nucleus is followed by the formation of cell wall.
2. Owing to this, the central cell is divided into a large micropylar cell and a small chalazal cell.
3. In both micropylar and chalazal chamber, the further development of the endosperm is of nuclear type.
4. Walls develop between nuclei in micropylar chamber.
5. This type of embryo development is seen in plants belonging to order Helobiales of Monocots. e.g. Asphodehis.
