Back to: Botany 300 Level
Hello, my brilliant friend! I hope you’re having a great day! Have you ever seen a plant grow from a small cutting or even a tiny piece of leaf? Or wondered how scientists produce thousands of identical plants in a lab? The secret lies in callus formation and organogenesis—two key processes in plant tissue culture. Today, we’ll learn how plants can regenerate from just a few cells, and why this is so important in agriculture, medicine, and conservation!
Callus formation and organogenesis
Understanding Callus Formation and Organogenesis
Plants have an amazing ability to heal and grow. When a part of a plant is wounded or removed, it can form a mass of cells called a callus. This callus can later develop into roots, stems, and leaves through a process called organogenesis.
What is Callus Formation?
A callus is an unorganised mass of plant cells that forms when plant tissue is grown under special conditions. It is like a “healing tissue” that appears when a plant is injured.
How does callus form?
A small piece of plant tissue (called an explant) is taken from a healthy plant (e.g., a leaf, stem, or root).
The explant is sterilised to remove bacteria and fungi.
It is placed in a nutrient-rich culture medium with plant hormones.
The cells divide rapidly, forming a soft, white, or yellow mass called a callus.
What is Organogenesis?
Once a callus has formed, it can be stimulated to grow into a whole plant through organogenesis. This is the process where plant organs (roots, shoots, and leaves) develop from the callus.
Types of Organogenesis:
Shoot Organogenesis – When the callus develops into shoots.
Root Organogenesis – When the callus forms roots first.
The process is controlled by two important plant hormones:
Auxins (like NAA and IAA) promote root formation.
Cytokinins (like BAP and Kinetin) promote shoot formation.
Steps in Callus Formation and Organogenesis
Callus Induction – The explant is placed in a culture medium containing high auxin levels to stimulate callus growth.
Shoot Formation – If the medium has high cytokinins, shoots begin to form.
Root Formation – If the medium has high auxins, roots begin to form.
Plantlet Development – The shoots and roots mature into small plants.
Hardening – The plantlets are transferred to soil and gradually adapted to natural conditions.
Why is Callus Formation and Organogenesis Important?
Plant Propagation – Produces thousands of identical plants from a small tissue sample.
Disease-Free Plants – Helps grow virus-free plants like bananas and cassava.
Genetic Modification – Allows scientists to introduce new traits, such as pest resistance.
Conservation – Helps save rare and endangered plants.
A Simple Story to Understand This Concept
Imagine you have a small piece of dough (callus). If you add different ingredients (plant hormones), you can shape it into bread, cake, or biscuits (roots, shoots, or leaves). Similarly, plant scientists use hormones to guide callus into forming different plant parts!
Summary
Callus formation is when plant cells grow into an unorganised mass after being placed in a culture medium.
Organogenesis is the process where shoots, roots, and leaves develop from the callus.
Auxins promote root growth, while cytokinins promote shoot growth.
Plant tissue culture using callus and organogenesis helps in mass production, genetic improvement, and conservation of plants.
Evaluation
- What is a callus, and how does it form?
- What is the role of auxins and cytokinins in organogenesis?
- Why is callus culture important in agriculture?
- What are the two types of organogenesis?
- How is callus formation used in plant conservation?
You are doing an amazing job! Now, the next time you see a laboratory-grown plant, remember that it started as a tiny callus! Keep learning with Afrilearn, and I’ll see you in the next exciting lesson. Stay curious and keep growing
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