Polyembryony has been defined as the occurrence of more than one embryo in a seed. Generally, the additional embryos in a seed may not reach the mature stage.
Poly embryony was first reported by Leeuwenhoek (1719) in some orange seeds.
Bouman and Bosenwinkel (1969) have clearly defined polyembryony as a phenomenon of occurrence of two or more proembryos in an ovule. They are of the opinion that .1 is an abnormal feature.
According to Braun (1859), there are four categories of polyembryony, on the basis of their origin.
It may arise by
1. Cleavage of zygote or zygotic embryo.
2. Formation of embryos by cells of the embryo sac other than the egg.
3. Activation of some initial sporophytic cells of the ovule.
4. Development of more than one embryo sac within the ovule.
Eames and Schnarf (1929) classified Polyembryony into two types. (1) True Polyembryony (2) False Polyembryony. The formation of plural embryos within a single embryo aac is designated as true polyembryony. In false polyembryony the embryos are derived from different embryo~8acs. False polyembryony takes place by the following three sources:-
(a) Formation of multiple embryo sac.
(b) Fusion of two or more ovules.
(c) Cleavage of the nucellus. TRUE POLYEMBRYONY
(a) Embryos arising within an embryo sac either by the cleavage of the zygote or from the synergids, antipodals or endosperm.
(b) Embryos arising from the tissues lying outside the embryo sac that is, from the cells of the nucellus or the integuments, although ultimately they come to lie within the embryo sac (adventive embryony).
