3 types of endosperm development in flowering plants

Formation of Endosperm

• The development of endosperm is first post fertilization events in flowering plants.

• The development of the endosperm is essential for the development of the embryo because endosperm provide nutrition for developing embryo therefore development of endosperm always occur before the development of embryo.

• The primary endosperm nucleus divides repeatedly and forms an endosperm.

• This endosperm is rich in nutrients and gives nourishment to the embryo for the development .

• In most common type of endosperm development, The primary endosperm nucleus undergo successive nuclear division and form many free nuclei.

• This stage of development of endosperm is called free nuclear endosperm.

• Subsequently, cell wall formation occurs and endosperm become cellular.

• The number of free nuclei are different from species to species.

• The coconut water is tender, an example of free nuclear endosperm and surrounding white kernel is cellular endosperm.

Types of seed on the basis of endosperm

• In some cases like Beans, pea ground nut etc, the endosperm is completely consumed by the embryo during development so there is no residue of endosperm in such seeds.

• Such seeds  are called non endospermic seeds or non albumious seed.

• Non endospermic seeds use their cotyledons for the storage of food material.

• In some seeds like Coconut, Castor etc endosperm is not completely consumed by the embryo during development so there is residue  of endosperm in such seeds.

• Such seeds  are called  endospermic seeds or albumious seed.

Types of endosperm

• On the basis of development, endosperm is of three types - Nuclear endosperm,cellular endosperm and Helobial endosperm. 

Nuclear endosperm -

• During the development of nuclear endosperm, the initial few divisions of primary endosperm nucleus are not supported by the cell wall formation therefore the produced nuclei by primary endosperm nucleus are free due to lack of cell wall formation.
• This type of  nuclear endosperm is found in Cocus nucifera.

• The liquid inside the cocus nucifera is known as liquid syncytium.

• The watery endosperm of coconut has coconut growth milk factor so it is used in culture experiments.

• In Arachis hypogaea, there is cell wall formation after the development of nuclear endosperm.

• Cellular endosperm is mostly found in dicotyledons.

• In this type of endosperm, cell wall formation starts with the first division of the primary endosperm nucleus and the cell wall that is formed is transverse.

• Afterwards, all divisions are irregular so there is no regular arrangement of tissue.

Helobial endosperm

• It is the transition state between the cellular and nuclear endosperm.

• The first division of the primary endosperm nucleus leads to the formation of a transverse wall.

• This wall divide embryo sac into chalazal and micropyle chamber. 

• After that there is a free nuclear division in both chambers but there is less nuclear division in the chalazal chamber and this portion frequently degenerates.

• The free nuclear division in the micropylar chamber followed by the  cell wall formation thus cellular endosperm is formed.

• In this way, the helobial endosperm is marked by the both nuclear and cellular endosperm.