Tissue culture is a laboratory-based technique where small pieces of living tissue (plant or animal) are grown in an artificial medium away from their natural environment. It is widely used in biology and has opened up many possibilities in plant breeding, agriculture, horticulture, and medical research. If you are wondering what tissue culture is in biology, it essentially exploits a cell’s ability to multiply and develop into a whole new organism (under ideal conditions).

This process is also called micropropagation when dealing with plants. It requires a sterile environment, well-prepared culture media (agar or liquid broth), and skilled personnel to ensure successful results. Farmers, researchers, and horticulturists often rely on tissue culture to develop tissue culture plants that are free from diseases and to produce large numbers of identical plants in a short time.

Types of Tissue Culture

Tissue culture can be classified based on the source of the explant (a small piece of tissue taken from the organism) and the purpose of the culture. Here are the main types:

Seed Culture

Involves growing seeds in vitro under sterile conditions.
Often used for research on seed germination or for producing seedlings free from pathogens.

Embryo Culture

An isolated embryo (mature or immature) is grown in an artificial medium.
Immature embryos may be used when normal seed germination fails.
This technique helps rescue embryos from hybrid crosses that do not develop fully within the seed.

Callus Culture

A callus is a mass of unorganised cells formed from an explant.
When placed on a nutrient medium with the right balance of plant growth regulators, the explant forms a callus, which can later differentiate into roots, shoots, or other organs.

Organ Culture

Any part of a plant (leaf, stem, root, shoot tip) is grown to preserve its structure and function.
Common methods include the raft method, plasma clot method, and agar gel method.

Protoplast Culture

Protoplasts are cells without cell walls.
Protoplast culture involves regenerating a complete cell wall around these cells and inducing them to divide and develop into a whole plant.
It can be used for genetic engineering because removing the cell wall makes it easier to introduce new genetic material.

Other Variants

Pollen Culture / Anther Culture: Produces haploid plants from pollen grains.
Single Cell Culture: Focuses on growing individual cells isolated from tissues.
Suspension Culture: Cells or small aggregates of cells suspended in a liquid medium.
Somatic Embryogenesis: Somatic (non-reproductive) cells develop into embryos and eventually form complete plants.

Steps Involved in Tissue Culture

The tissue culture process in plants typically follows these steps:

Initiation

A small piece of tissue (explant) is removed from the parent plant.
The explant is thoroughly sterilised to prevent bacterial or fungal contamination.

Multiplication (Callus Formation)

The sterilised explant is placed on a nutrient medium containing essential minerals, vitamins, and hormones.
Cells begin to multiply and form an undifferentiated mass of tissue called callus.

Root Formation

Specific plant growth regulators (auxins) are added to induce roots.
Once the roots appear, the tissue is transferred to a different medium if necessary.

Shoot Formation

Cytokinins or a suitable combination of hormones stimulate shoot development.
Small shoots start emerging from the callus or directly from the explant.

Acclimatisation

Once shoots and roots develop into tiny plantlets, they are gradually exposed to greenhouse conditions.
After adjusting to controlled conditions, the healthy plantlets are moved to nurseries or fields to continue growing in natural settings.

Advantages of Tissue Culture

Many advantages of tissue culture make it a valuable technique:

Disease-Free Plants: Tissue culture plants are often free of pathogens, as the process uses sterilised tissue.
Mass Propagation: Large numbers of genetically identical plants can be produced rapidly.
Year-Round Production: Plants can be grown at any time, regardless of seasonal constraints.
Space Efficiency: Minimal space is required compared to traditional field propagation.
Accelerated Breeding: New varieties can be introduced faster into the market.
Wide Application: Useful for ornamental, medicinal, and crop plants.

Importance of Tissue Culture

Tissue culture plays a crucial role in biology, agriculture, and many other fields:

Crop Improvement and Breeding

If you’re wondering what tissue culture is in agriculture, it is a method to rapidly multiply disease-free, high-yielding crop varieties.

Genetic Engineering

Used for what is tissue culture in plants to introduce desirable traits such as pest resistance or stress tolerance.

Conservation of Rare Species

Rare or endangered plants can be cloned to preserve biodiversity.

Animal Tissue Culture

Although most people think of plants when they ask what tissue culture is, this technique also applies to animal tissues. It helps research in cell biology, vaccine production, and medical diagnostics.

Medical and Pharmaceutical Applications

Producing secondary metabolites from plant cells or regenerating tissues for transplant research in animals.

Tissue Culture Examples

There are numerous tissue culture examples in various fields:

Food Crops: Oil palm, banana, pineapples, tomatoes, sweet potatoes.
Industrial Crops: Rubber tree, sugarcane.
Horticultural Plants: Orchids, chrysanthemums, dahlia.
Medicinal Plants: Aloe vera, neem, and many others used in pharmaceutical research.

Additional Insights

Below are a few extra bits of information to make learning about tissue culture more interesting and memorable:

Historical Note: The concept of plant tissue culture was first introduced in the early 20th century by researchers who observed that plant cells have the ability to regenerate a whole plant, thanks to their totipotent nature.
Key Difference from Traditional Propagation: Traditional methods rely on seeds or cuttings. Tissue culture, by contrast, uses small pieces of tissue grown in controlled conditions, making it more precise and efficient in producing identical offspring (clones).

Quiz

Test your understanding of tissue culture with these quick questions:

Which part of the plant is used in organ culture?
A. Leaves or shoots
B. Seeds only
C. Roots only
D. Pollen grains
Answer: A (Leaves or shoots can be used in organ culture)

What is a callus in tissue culture?
A. A group of differentiated cells that stop dividing
B. A group of undifferentiated cells that keep dividing
C. An organ formed by the plant directly
D. A natural protector on the plant stem
Answer: B (A callus is a mass of undifferentiated cells that keep dividing)

Which hormone primarily promotes root formation?
A. Cytokinin
B. Auxin
C. Gibberellin
D. Ethylene
Answer: B (Auxins help in root initiation)

Name a crop commonly produced by tissue culture in agriculture:
A. Banana
B. Maize (only by seeds)
C. Onion (only by bulbs)
D. All of the above
Answer: A (Banana is a well-known example)

FAQs on Tissue Culture: Definition, Types, Steps, and Applications

1. Can tissue culture be done at home?

While small-scale experiments can be tried at home using simple plant tissues, successful tissue culture typically requires sterile conditions, precise temperature control, and specific growth media.

2. Is tissue culture limited to plants only?

No. Tissue culture can also be used to grow animal cells and tissues. However, most people are familiar with what tissue culture is in plants because it is widely used in horticulture and agriculture.

3. Why is sterility important in tissue culture?

Sterility is crucial because any contamination by bacteria or fungi can spoil the culture and prevent the tissues from growing properly.

4. What is the difference between callus culture and organ culture?

Callus Culture: Focuses on growing undifferentiated cells that can later form shoots or roots.
Organ Culture: Involves culturing specific organs (like leaves or shoot tips) to maintain their structure and function.

5. Which hormones are commonly used in tissue culture?

Auxins (for root initiation) and cytokines (for shoot initiation) are the most commonly used plant growth regulators. They are crucial for guiding cells to differentiate into roots or shoots.

6. How does tissue culture help in agriculture?

If you are looking for what tissue culture is in agriculture, it’s a method that ensures high-quality, disease-free planting material on a large scale. This leads to better crop yields and more uniform produce.