What is the Difference Between Organogenesis and Somatic Embryogenesis

The main difference between organogenesis and somatic embryogenesis is that organogenesis is the induction of vegetative tissue to form organs whereas somatic embryogenesis is the induction of vegetative tissue to form an embryonic callus. Furthermore, organogenesis causes the development of a plantlet with root and shoot while somatic embryogenesis leads to the formation of a somatic embryo.

Organogenesis and somatic embryogenesis are two pathways used in plant tissue culture for the vegetative propagation of plants.

Key Areas Covered

1. What is Organogenesis
     – Definition, Process, Types
2. What is Somatic Embryogenesis
     – Definition, Process, Types
3. What are the Similarities Between Organogenesis and Somatic Embryogenesis
     – Outline of Common Features
4. What is the Difference Between Organogenesis and Somatic Embryogenesis
     – Comparison of Key Differences

Key terms

Auxin, Callus, Organogenesis, Plant Growth Regulators, Somatic Embryogenesis

What is Organogenesis

Organogenesis is a method used by plant tissue culture to induce plant organs including shoot and root from vegetative tissue. It eventually develops a complete plantlet, i.e., a small, but whole plant. Also, plant growth regulators (PGRs) or cytokinins are responsible for the induction of vegetative tissue into plant organs. For this, one can use different concentrations of 6-benzylaminopurine (BAP) alone or in combination with an auxin. Naphthalene Acetic Acid (NAA) and 2,4-Dichlorophenoxyacetic acid (2,4-D) are two types of synthetic auxins suitable for this process. 

Figure 1: Organogenesis in Plants

Based on the procedure, organogenesis has two categories. They are direct and indirect organogenesis. In direct organogenesis, the explant or the original part of the plant used to initiate the culture develops into the shoot and root directly. However, in indirect organogenesis, the explant proceeds through a callus phase during the organogenesis.  

Figure 2: Organogenesis is Animals

Furthermore, organogenesis is a natural process that occurs in both plants and animals. In plants, apical meristem produces the lateral plant organs continuously until the plants die. In animals, organogenesis occurs in the embryonic development following gastrulation. Here, the three germ layers developed as a result of gastrulation form internal organs of the body.

What is Somatic Embryogenesis

Somatic embryogenesis is another method used by plant tissue culture. This involves the development of an embryonic callus from a piece of vegetative tissue. It leads to the development of a somatic embryo that can germinate to form a complete plantlet. Plant growth regulators play a key role in the induction of somatic embryogenesis. Here, auxins are used at the initial stages of the development; after that, abscisic acid is used in the final stages. Especially, NAA is an effective form of auxin in somatic embryogenesis. Higher concentrations of NAA may produce yellowish-white compact calli.

Figure 3: Calli

Same as organogenesis, somatic embryogenesis consists of two categories based on the process: direct somatic embryogenesis, in which the embryo develops directly from the explant, and indirect somatic embryogenesis, in which the development of embryo proceeds through a callus-forming stage.

Similarities Between Organogenesis and Somatic Embryogenesis

• Organogenesis and somatic embryogenesis are two pathways used in plant tissue culture for the vegetative propagation of plants.
• They are alternative methods to the direct shoot induction.
• Also, both methods involve in the induction of vegetative tissue with the use of different plant growth regulators.
• Auxin is a common plant hormone used in both methods.
• They are responsible for obtaining a large number of plantlets under laboratory conditions.
• The original plant used in the initiation of the culture is known as the explant.
• Both processes can be classified as direct and indirect method.

Difference Between Organogenesis and Somatic Embryogenesis

Definition

Organogenesis refers to the series of organized integrated processes which transform an amorphous mass of cells into a complete organ in the developing embryo while somatic embryogenesis refers to an artificial process in which a plant or embryo is derived from a single somatic cell. Thus, this is the fundamental difference between organogenesis and somatic embryogenesis.

Significance

The major difference between organogenesis and somatic embryogenesis is that organogenesis is the process which generates plant organs including shoot and root from vegetative tissue while somatic embryogenesis is the process which generates embryonic callus from vegetative tissue.

Occurrence

Also, while organogenesis is a natural process and it can also be induced artificially, somatic embryogenesis is an artificial process that occurs under laboratory conditions.

Hormonal Signal

The hormonal signal is another difference between organogenesis and somatic embryogenesis. Organogenesis proceeds through two hormonal signals to induce shoot and then the root separately while somatic embryogenesis proceeds through a single hormonal signal.

Result

Moreover, organogenesis results in the formation of a complete plantlet with shoot and root while somatic embryogenesis results in the formation of a somatic embryo. This is another major difference between organogenesis and somatic embryogenesis.

Vascular Connection

Besides, the shoots and roots developed by organogenesis have a strong connection with their maternal tissue while the somatic embryos formed by the somatic embryogenesis have no vascular connection with the maternal callus.  

Conclusion

Organogenesis is the process of developing organs from the vegetative tissues in plants. It is responsible for the formation of complete plantlets with shoot and root. In comparison, somatic embryogenesis is the process of developing somatic embryos from vegetative tissue. Different types of plant growth regulators are involved in both processes. However, the main difference between organogenesis and somatic embryogenesis is the resultant plant structure.

References:

1. Chieng L.M.N., Chen T.Y., Sim S.L., Goh D.K.S. (2014b): Induction of Organogenesis and Somatic Embryogenesis of Gonystylus bancanus (Miq.) Kurz (Ramin) in Sarawak. Kuching, Sarawak Forestry Corporation & ITTO: Available Here.

Image Courtesy:

1. “Cercis yunnanensis -3” By Joshnadler (talk) – Own work (Original text: I created this work entirely by myself.) (Public Domain) via Commons Wikimedia    
2. “Callus1” By Igge – Own work (CC BY-SA 3.0) via Commons Wikimedia  
3. “Germ layers” By CNX (CC BY-SA 3.0) via Commons Wikimedia