What is endosperm ? Explain the types.

Explanation

Endosperm : The primary endosperm nucleus (PEN) divides immediately after fertilization but before the zygote starts to divide , into an endosperm . The primary endosperm nuleus is the result of triple fusion (two polar nuclei and one sperm nucleus) and thus has 3n number of chromosomes. It is nutritive tissue and regulatory structure the nourishes the developing embryo. Depending upon the mode of development three types of endosperm are recognized in angiosperms. They are nuclear endosperm cellular endosperm and helobial endosperm.

Nuclear endosperm : primary Endosperm Nucleus undergoes several mitotic division without cell wall formation thus a free nuclear condition exists in the endosperm.
Examples : Coccinia , Capsella and Arachis.
Cellular endosperm :
Primary endosperm nucleus divides into 2 nuclei and it is immediately followed by wall formation . Subsequent divisions also follow cell wall formation.
Examples : Adoxa , Helianthus and Scoparia.
Helobial endosperm : Primary Endosperm Nucleus moves towards base of embryo sac and divides into two nuclei. Cell wall formation.
Helobial endosperm : Primary Endopserm Nucleus moves towards base of embryo sac and divides into two nuclei. Cell wall formation takes place leading to the formation of a large micropylar and small chalazal chamber. The nucleus of the micropylar chamber undergoes several free nuclear division whereas that of chalazal chamber may or may not divide.
Example : Hydrilla and Vallisneria.
Ruminate endosperm : The endosperm with irregularity and unevenness in its surface forms ruminate ndosperm . Examples : Areca catechu, Passiflora and Myristica.