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examBoard: Pearson Edexcel
examType: IGCSE
lessonTitle: Tissue Culture Techniques
Tissue culture is a fascinating method of growing plants in a laboratory setting without soil. It's a type of cloning where we can create exact copies of a plant using just small pieces of plant tissue. This technique is incredibly important in modern agriculture, horticulture and conservation efforts.
Key Definitions:
Tissue culture allows us to produce thousands of identical plants quickly. It's especially useful for plants that are difficult to grow from seeds or cuttings. Many of the houseplants, orchids and fruit trees you see in shops have been produced using tissue culture techniques!
Tissue culture is a type of cloning because all the new plants produced are genetically identical to the parent plant. This means they're all clones with exactly the same characteristics and DNA as the original plant.
Tissue culture involves several carefully controlled steps that must be followed precisely to be successful. Let's explore the main stages:
Before any tissue culture can begin, everything must be extremely clean to prevent contamination.
Choose a healthy, disease-free plant with desirable characteristics.
Small pieces of plant tissue (often shoot tips or leaf segments) are carefully cut from the parent plant.
The explant is treated with chemicals like bleach or alcohol to kill any microorganisms on the surface.
Once sterilised, the explant is placed onto a nutrient medium in a sterile container.
The medium contains all the nutrients, vitamins, minerals and plant hormones needed for growth. It's usually made with agar (a jelly-like substance) so plants have something to grow on. Different plants need different recipes!
The cultures are kept in growth rooms with carefully controlled temperature, light and humidity. These conditions are optimised for each plant type.
This is where the real magic happens! The explant begins to grow and multiply.
Plant hormones in the medium (especially cytokinins) encourage the tissue to produce multiple shoots instead of just growing bigger. These shoots can then be separated and placed on fresh medium, where each will grow into a new plantlet. This process can be repeated many times, allowing scientists to produce thousands of plants from just one original explant!
A single plant explant can theoretically produce millions of new plants in just one year through repeated multiplication cycles. This is why tissue culture is so valuable for rare plant conservation and commercial production.
Once enough shoots have been produced, they need to develop roots.
The shoots are transferred to a different medium containing auxins (plant hormones that stimulate root growth). After a few weeks, the shoots develop roots and become complete plantlets with both shoots and roots.
The final challenge is getting the plants ready for the outside world.
Plants grown in tissue culture have been living a pampered life! They've had perfect conditions, plenty of nutrients and high humidity. They need time to adjust to normal growing conditions. This process is called hardening off or acclimatisation.
The plantlets are carefully removed from their containers and planted in sterile potting mix.
They're kept in high humidity at first, then gradually exposed to normal air, stronger light and temperature fluctuations.
Mass production of disease-free fruit trees, banana plants and other crops. Tissue culture has revolutionised banana production worldwide!
Production of millions of identical ornamental plants like orchids, ferns and houseplants for the global market.
Saving endangered plant species by growing large numbers from limited source material and creating living gene banks.
In the 1950s, the world's most popular banana variety, the Gros Michel, was nearly wiped out by a fungal disease called Panama disease. Tissue culture helped save the banana industry by allowing rapid production of disease-resistant Cavendish bananas, which is the variety most commonly eaten today. Currently, scientists are using tissue culture to develop new banana varieties that are resistant to a new strain of Panama disease that threatens the Cavendish.
Tissue culture isn't just useful for cloning plants – it's also an essential tool for creating genetically modified (GM) plants. When scientists want to introduce new genes into a plant, they often use tissue culture as part of the process:
This combination of tissue culture and genetic engineering has led to the development of crops with improved characteristics such as disease resistance, drought tolerance and enhanced nutritional value.
Tissue culture techniques continue to evolve and improve. Researchers are developing new methods to culture plants that have traditionally been difficult to propagate this way. They're also working on automated systems that can reduce costs and make tissue culture more accessible.
As climate change threatens plant biodiversity and food security, tissue culture will play an increasingly important role in preserving plant species and developing crops that can thrive in changing conditions.
Similar tissue culture techniques are also used with animal cells for research and medical applications, including growing skin for grafts and developing new drugs. The principles of providing the right nutrients and conditions for cells to grow outside their natural environment are the same, though the specific requirements differ between plant and animal cells.
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