Embryogenesis is the process by which a plant embryo develops from a fertilized ovule. It involves asymmetric cell division and differentiation of unspecialized cells into tissues and organs. There are two types of embryos: zygotic embryos formed from the zygote, and non-zygotic embryos like somatic and parthenogenic embryos formed from non-zygote cells. Somatic embryogenesis is the process where somatic cells develop into embryos and can regenerate whole plants. It occurs through direct or indirect routes. Key stages of somatic embryogenesis include globular, heart, torpedo and mature stages. Growth regulators like auxins and cytokinins play an important role in somatic embryogenesis.

1. EMBRYOGENESIS
Prepared by: M. Saqib Sheraz
4/9/2019 5:11:58 PM 1

2. Embryogenesis
 Embryogenesis is the process that produces a plant embryo from a
fertilized ovule by asymmetric cell division and the differentiation of un-
differentiated cells into tissue and organ is called embryogenesis.
 It takeplace during seed development, when the single celled zygote
undergoes a programmed pattern of cell division resulting in a mature
embryo.
2

3. Classification of embryos:
 In 1978, H.W Kohlehbach proposed the following classification.
1. Zygotic embryo: It is formed by the zygote.
2. Non-zygotic embryo: It is formed from the cells other than zygote. It is
of following types.
a. Somatic embryo: It is formed from somatic cells in-vitro.
b. Parthenogenic embryo: It is formed by un-fertilized egg.
c. Androgenic embryo: It is formed by pollen grains.
3

4. Somatic Embryogenesis
 Somatic embryogenesis is a process by which somatic cells or tissues
develops into differentiated embryos.
 Embryos regenerate from somatic cells or tissues ( haploid or diploid etc) it
is termed as Somatic Embryogenesis.
 Somatic embryogenesis was first induced in suspension culture (Stewart
et al, 1958) and in callus culture (Reinert, 1959) of carrot, Umbelliferae and
Solanaceae dicotyledonous families have produced somatic embryos.
4

5. Nutritional Media
 Two nutritional media of different composition are required to obtain
embryoids.
1. First medium contains auxins to initiates embryogenic cells.
2. Second medium lacks auxin or reduced level of auxins is needed for
subsequent development of the embryonic cells into embryoids and
plantlets.
5

6. STAGES OF SOMATIC
EMBRYOGENESIS
4/9/2019 5:11:58 PM 6

7. Continue…
 Globular stage: Embryo is small and round (multicellular).
 Heart stage: Shape changes to heart shape with more
cotyledon development.
 Torpedo shaped stage: Consists of initial cells for the
shoot/root meristem.
 Mature stage: Embryo becomes cylindrical or cotyledonary
shape.
7

8. Routes of Somatic Embryogenesis
 Two routes to somatic embryogenesis
 Direct somatic embryogenesis:
 The embryos initiate directly from explants in the absence of callus
formation.
 This occurs through pre-embryonic determined cells (PEDC). Such cells
are found in embryonic tissues.
 Indirect somatic embryogenesis:
 Callus from explants takes place from which embryos are developed.
 This occurs through Induced embryogenic determined cells (IEDC).
8

9. Factors effecting Somatic
Embryogenesis
1. Genotype of explants: Explant genotype has a marked influence on
somatic embryo regeneration and in many cases, it may determine
whether or not somatic embryo regeneration will occur.
 2. Growth regulators:
• Auxins: Auxin alone or in combination with cytokinin appear essential for
the onset of growth and the induction of embryogenesis of all the auxins, 2,4-
D followed by NAA have proven to be extremely useful.
• Effective concentration ranges are 0.5 – 27.6 μ M for 2,4-D and 0.5 – 10.7 μ
M for NAA.
9

10. Continue…
 Cytokinins: CKs have been used in the primary medium invariably during
embryogenesis of crop plants.
• Effective concentrations for kinetin0.5 – 50.0μ M. CKs are important in
fastening somatic embryo maturation and especially cotyledon development
3. Nitrogen source: Form of nitrogen has marked influenced on somatic
embryogenesis. In carrot NH₄⁺ form has a promotive effect.
• Somatic embryos development occurs on a medium containing NO₃⁻ as the
sole nitrogen source.
10

11. Advantages and Disadvantages
 Advantages
 Suitable for suspension culture.
 Somaclonal variation.
 Artificial seed production.
 Labour savings.
 Disadvantages:
 Low frequency embryo production.
 Incomplete embryo production
11

12. Thank You
12