Introduction to Somatic Embryogenesis
In angiosperms, ovules are developed within the ovary. Within the ovules, a sac like structure known as embryo sac lies embedded into nucleus. The embryo sac represents the female gametophyte of angiosperms. The ovule contains a haploid egg cell or ovule which is female reproductive cell or female gamete. During fertilization, the male gamete fuses with egg cell or female gamete. During fertilization, the male gamete fuses with egg cell or female gamete resulting in formation of an unicellular zygote or oospore. The zygote gives rise to multicultural embryo, cells of which are diploid. Embryos derived in this sexual process are known as zygotic embryo, and process of embryo development is called embryogenesis. Sometimes, embryo is formed by the unfertilized egg and such embryos are called parthenocarpic embryo. Again sometimes, any cell of the female gametophyte or Sporophytic tissue around the embryo sac may give rise to an embryo and such embryos are called non zygotic embryos. In nature there are no instances of ex-ovule embryo development. therefore, there is no evidence of embryo development in vitro from any somatic cells of the plants. That means, in vivo somatic plant cells do not express any embryogenic potential to form embryo.
In plant tissue culture, the developmental pathway of numerous well organised, small embryoids resembling the zygotic embryos form the embryogenic potential somatic cell of callus tissue or cells of suspension cultures is known as somatic embryogenesis.
The capacity of somatic cell of a culture to produce embryoids is known as embryogenic potential.