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Plant embryogenesis is a fascinating developmental programme that has been found to be very successful in nature in seeds. Asynchronous differentiation and further development of somatic embryos, malformations and disturbed polarity, precocious germination, lack of maturity, early loss of embryogenic potential, and strong genotypic differences in regeneration efficiency are all limitations of in vitro somatic embryogenesis. Several studies have found morphological, histological, biochemical, and physiological similarities between somatic and zygotic embryos. However, pronounced differences have been reported, referring to much higher stress levels, less storage compound accumulation, and a failure to distinguish differentiation and germination by a quiescent phase in somatic embryos.
A review of recent literature describing both embryogenesis pathways, comparing somatic and zygotic embryos, and examining the role of the endosperm is provided here. Somatic embryogenesis can be improved and optimised by using zygotic embryos as a reference and learning from the situation in seeds in order to take advantage of the enormous potential the regeneration pathway offers for the plant propagation and the breeding.
What is Embryogenesis?
The formation of an embryo is referred to as embryogenesis. Embryogenesis begins with a single embryogenic cell, which can be a zygote (the result of an egg and sperm fusing during fertilisation) or an undifferentiated callus cell. Embryos derived from zygotes are referred to as zygotic embryos, while those derived from somatic cells are referred to as somatic embryos.
During embryonic development, the plant’s polar axis is established, domains that organise the plant body are defined, and the primary tissue and organ systems are defined. In plant tissue culture, another important way to regenerate new plants is through somatic embryogenesis. Embryo development is a highly organised series of cell division, enlargement, and differentiation.
The gross development pattern of zygotic and somatic embryos is the same. Both types of embryos develop in the same way, going through the same developmental stages. Embryo development is bipolar, with a shoot pole at one end and a radicular pole at the other. Because embryos are structurally independent of their parent body, they are not organs.
What is Somatic and Zygotic Embryogenesis?
Zygotic
In higher plants, zygotic embryogenesis describes the developmental period during which the zygote goes through a series of differentiation events that leads to the formation of a mature embryo. The formation of the major embryonic organs, as well as shoot and root apical meristems, occurs through partitioning events along the apical–basal axis, and many of these events are influenced by the hormone auxin. The three embryonic tissue systems develop along a radial axis that is perpendicular to the apical–basal axis. The mature zygotic embryo is generally developmentally arrested, metabolically quiescent, and contained within the seed’s maternal tissues.
Somatic
Somatic embryogenesis is a process in which somatic cells are induced to diverge from their normal fate and develop into embryos. Auxin and other plant hormones appear to be important in the induction of embryogenic competence. Parallel developmental programmes in which cells acquire embryogenic cell fate and develop into mature embryos are known as zygotic and somatic embryogenesis.
Difference between Somatic Embryogenesis and Zygotic Embryogenesis of Zygotes
S.NO | Somatic Embryogenesis | Zygotic Embryogenesis |
1 | Somatic embryogenesis is the process by which plant somatic cells are stimulated to form embryos. | The process of forming an embryo as a result of double fertilisation of the ovule is known as zygotic embryogenesis. |
2 | There is less food available for embryos. | It stores carbohydrate and protein for the embryo. |
3 | It is a synthetic, in-vitro process. | It is a natural occurrence. |
4 | Somatic embryos do not develop endosperm or a seed coat. | In zygotic embryos, both endosperm and seed coat are formed. |
5 | Asexual reproduction is possible. | Reproductive Sexuality |
6 | The embryo has no vascular connection to the explant from which it developed. | The embryo and the explant have well-connected vasculature. |
7 | It lacks a quiescent resting phase and proceeds directly to somatic embryogenesis. | Zygotic embryogenesis follows the correct morphogenesis and maturation phase pathway. |
Conclusion
The formation of an embryo is referred to as embryogenesis. Somatic embryogenesis is a process in which somatic cells are induced to diverge from their normal fate and develop into embryos. The process of forming an embryo as a result of double fertilisation of the ovule is known as zygotic embryogenesis. A review of recent literature describing both embryogenesis pathways, comparing somatic and zygotic embryos, and examining the role of the endosperm is provided here. Somatic embryogenesis can be improved and optimised by using zygotic embryos as a reference and learning from the situation in seeds in order to take advantage of the enormous potential there are the regeneration pathway offers for the plant propagation and the breeding. The formation of an embryo is referred to as embryogenesis. The gross development pattern of zygotic and somatic embryos is the same.
