What is the Difference Between Callus and Plantlet

The main difference between callus and plantlet is that the callus is a cell mass whose cells develop into plantlets in the plant tissue culture whereas, the plantlets are young or small plants used as propagules. 

Callus and plantlet are two structures of plants that help in the vegetative propagation. Furthermore, a callus consists of unorganized cells while the plantlet have organized cells as stem, root, and leaves. Moreover, the formation of plantlets from the cells in a callus is a method of micropropagation, which is an artificial method. However, some plants naturally produce plantlets as a part of their vegetative propagation.

Key Areas Covered

1. What is Callus
     – Definition, Structure, Importance
2. What is Plantlet
     – Definition, Structure, Importance
3. What are the Similarities Between Callus and Plantlet
     – Outline of Common Features
4. What is the Difference Between Callus and Plantlet
     – Comparison of Key Differences

Key Terms

Apomixis, Callus, Micropropagation, Plant Growth Regulators, Plant Tissue Culture, Plantlet

What is Callus

A callus is a mass of cells used to produce new plants in plant tissue culture. Living plants also contain calli and the cells of the callus cover plant wounds. It consists of an unorganized, parenchyma cells. After induction, these cells develop into individual plants. Here, plant growth regulators like cytokinins, auxins, and gibberellins are responsible for the initiation of callus formation from explants. And, this process is known as somatic embryogenesis. All the major groups of land plants are capable of producing callus on an appropriate tissue culture medium.

Figure 1: Calli

The callus induction medium contains agar, macronutrients, and micronutrients. The main types of basal salt mixtures used are Murashige and Skoog medium, White’s medium, and woody plant medium. Nitrogen, phosphorus, and potassium are especially important in callus formation. The cells in the callus directly undergo organogenesis or embryogenesis under the influence of plant growth regulators in the tissue culture medium.

What is Plantlet

Plantlet is a small, young plant produced by the cells of the callus in plant tissue culture. As mentioned before, after the induction of the callus by plant growth regulators or plant hormones, the cells produce roots and shoots that can further develop into new, small plants. They are extremely small but, contain all the organs of a typical plant of the species. Therefore, the plantlets produced from a callus are suitable for artificial, vegetative propagation. And, this method is known as micropropagation.

Figure 2: Banana Plantlets

In addition, some plants produce plantlets as vegetative propagules. The replacement of seeds of a plant by plantlet formation is a type of apomixis. The other type of apomixis is the replacement of flowers by bulbils. The main importance of plantlets is the production of many plants that are clones of the mother plant.

Similarities Between Callus and Plantlet

• Callus and plantlet are two types of plant structures that aid in vegetative propagation.
• Both produce a large number of small plants at once.
• All the individuals of the offspring are genetically identical to the parent plant.

Difference Between Callus and Plantlet

Definition

A callus refers to a hard formation of tissue, especially new tissue formed over a wound, while a plantlet refers to a little plant, as one produced on the leaf margins of a kalanchoe or the aerial stems of a spider plant. Thus, this is the main difference between callus and plantlet.

Correspondence

A callus is a mass of cells used in plant tissue culture while plantlets are small plants developed from the cells of the callus.

Organization

The organization is also a major difference between callus and plantlet. Callus is an unorganized structure while the plantlets have organized structures as root, stem, and leaves.

Natural/Artificial

Moreover, the production of new plants from a callus is an artificial method while plantlets naturally occur in some plants.

Importance

The callus is important in the micropropagation of plants while plantlets are important as vegetative propagules. Hence, this is another difference between callus and plantlet.

Conclusion

A callus is a mass of cells used in the plant tissue culture. These cells can develop into small plants by inducing them with hormones. Plantlets are the small plants developed from the callus. In addition, some plants naturally produce plantlets as vegetative propagules. Therefore, the main difference between callus and plantlet is their structure and importance. Both calli and plantlets are important in the micropropagation of plants. 

References:

1. Dahanayake, N, and A L Ranawake. “Callus Induction and Plantlet Regeneration Ability of Selected Sri Lankan Traditional Rice Cultivars (Oryza Sativa L.) in Caryopses Culture.” Tropical Agricultural Research and Extension, vol. 15, no. 2, 2013, p. 15., doi:10.4038/tare.v15i2.5244.

Image Courtesy:

1. “Callus1” By Igge – Own work (CC BY-SA 3.0) via Commons Wikimedia  
2. “Banana plantlets transferred to soil (with vermicompost) from plant media” By Joydeep – Own work (CC BY-SA 3.0) via Commons Wikimedia