Endosperm
Formed as a result of double fertilization.
Primary endosperm nucleus (PEN) is the progenitors of endosperm in most of the angiosperms.
Absent in some families like Orchidaceae, Podostemaceae, and Trapaceae.
Serve as storage tissue .
Store carbohydrates (Paddy, wheat and maize), proteins (in aleurone layer of cereals) or fatty oils (Coconut, Castor bean).
Absorbed after germination in endospermous or albuminous seeds and before the complete development of embryo in non endospermous or exalbuminous seed.
CYTOLOGY OF ENDOSPERM
it is triploid (3n) in most of the angiosperms.
Ploidy level depends upon the participating polar nuclei of the embryo sac.
It is haploid (1n) in Balanophora, diploid (2n) in Oenothera and Butomopsis, triploid (3n) in most of the angiosperms (e.g. Polygonum), pentaploid (5n) in Fritillaria, Plumbagella, Penaea and Plumbago, nonaploid (9n) in Acalypha indica and many Pepromia species and decapentaploid (15n) in Pepromia hispidula.
Can be as high as 385n in Thesium alpinum, and 2,072n in Echinocystis lobata.
High level of ploidy in endosperm have been attributed due to endomitosis and nuclear fusion by Kapoor (1962).
Rarely, as in Crinum, Matthiola, Raphanus and Viscum, endosperm cells may contain chlorophyll and are green in colour.

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