Endosperm : Its Development and Significance - Practice Questions & MCQ

• Endosperm development precedes embryo development.
• The primary endosperm cell divides repeatedly and forms a triploid endosperm tissue.
• The cells of this tissue are filled with reserve food materials and are used for the nutrition of the developing embryo.
• The endosperm is predominantly a triploid tissue. 
• However, it is diploid in all the members of the family Onagraceae (evening primrose family) and pentaploid in Fritillaria. 
• Endosperm development is a characteristic feature of all families of angiosperms except Orchidaceae, Podostemaceae and Trapaceae. 

Types of Endosperm Formation:

• There are three general types of endosperm formation:
  • Nuclear type
  • Cellular type
  • Helobial type

Nuclear Endosperm:

• In this type, the first division and usually several of the following divisions are unaccompanied by wall formation. 
• The nuclei may either remain free or in later stages, they may become separated by walls.
• As divisions progress, the nuclei are being pushed towards the periphery, thus a large central vacuole is formed. 
• Often the nuclei are especially aggregated at the micropylar and chalazal ends of the sac and form only a thin layer at the sides.
• Coconut milk is an example of the nuclear endosperm.

Cellular Endosperm:

• In this type, every division of the primary endosperm nucleus is followed by cytokinesis.
• Hence, endosperm becomes cellular from the very beginning.
• For example, balsam.

Helobial Endosperm:

• It occurs in the order helobiales in monocot.
• This is an intermediate type of endosperm.
• The first division is followed by transverse cytokinesis to form two unequal cells, larger micropylar cell and smaller chalazal cell.
• Further development in both cells is nuclear.

Fate of Endosperm:

• The endosperm may either be completely consumed by the developing embryo (e.g., pea, groundnut, beans) before seed maturation.
• Such seeds are called non-endospermic or exalbuminous.
• It may persist in the mature seed (e.g. castor and coconut) and be used up during seed germination. 
• Such seeds are called endospermic or albuminous.