Polyembryony- its Types and Practical importance.pptx

Polyembryony- its Types and Practical importance

1. Yogesh Sharma Assistant Professor Department of Botany GDC Akhnoor Polyembryony : Types and Practical importance:-

2. The occurrence of two or more embryos in one ovule is called as Polyembryony . First time noticed by Leeuwenhoek (1719) in the seeds of orange. It is quite common amon conifers.Except for a few taxa ( i.e. Citrus , Mangifera ), Polyembryony occurs only as an abnormal feature. According to Ernst and Shcnarf (1929) Polyembryony may be true or False depending upon whether the embryos arise in the same or in different embryo sacs in the same ovule. Introduction

3. Various type of true polyembryony are: Cleavage polyembryony : Cleavage of the zygote or earlier stages of its development ( proembryo ) into two or more units. It is common in gymnosperms, but it is of rare occurrence in angiosperms. Embryos from cells of embryo sac other than egg: The embryo may appear from synergids and antipodal cells in the embroy sac. it arises from fertilized synergid (diploid) or unfertilized synergid (haploid).

4. Embryos arising from the cells outside embryo sac: Cells of the nucellus and integuments have also been observed to develop into embryos e.g. Citrus, Eugenia and Mangifera . Embryos from endosperm: Embryos developing from endosperm have been reported in Balanophora,Alnus . Polyembryony may be spontaneous which includes instances of naturally occurring polyembryony . Induced polyembryony includes instances of experimentally used cases.

5. Nucellar adventive embryos provide uniform seedlings of parental type as obtained through vegetative propagation.Moreover , nucellar embryos are free from disease. In vitro Somatic embryogenesis is looked upon as a practical approach to large scale propagation of selected genotypes. These somatic embryos can also be converted into artificial seeds by encapsulating individual somatic embryos with a hydrogel , such as Ca-alginate. Unlike shoot buds, Somatic embryos arise from single cells and therefore the new strains of plants obtained through embryogenesis would be solid mutants. Somatic embryogenesis provides an excellent opportunity for the molecular biology studies of embryogenesis of plants for e.g. Carrot and Arabidopsis . Practical applications of polyembryony :

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