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  4. In which of the following polyembryony commonly occurs ?

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Q. In which of the following polyembryony commonly occurs ?

NTA AbhyasNTA Abhyas 2020

Solution:

Polyembryony- The phenomenon of development of more than one embryo in one ovule, seed or fertilized ovum is called polyembryony.
Polyembrony is of two types-
  1. Induced polyembryony- It includes cases of experimentally induced polyembryony.
  2. Spontaneous polyembryony- It includes cases of naturally occurring polyembryony.
The types of spontaneous polyembryony given by Webber are-
  • Cleavage polyembryony- A single fertilized egg breaks into two or more, i.e, undergoes cleavage and gives rise to a number of embryos.
  • Apogamy- Embryos may be produced sometimes due to fertilization of cells of embryo sac other than the egg. The most common source is synergid. Production of Embryos from antipodal cells are rare.
  • Adventive polyembryony- Embryos originate from diploid cells of ovule lying outside embryo sac and either belong to integuments or nucellus. This type of embryony is common amongst citrus fruits. The embryos are rich in protoplasm and divide actively to produce small masses of cells that protrude into the embryo sac and eventually form true embryos and are distinguishable from the ones developed from egg cell due to lack of suspensor.