Section 1 of 4Stages of Micropropagation
Micropropagation is a form of tissue culture in which tiny pieces of a plant are grown on a nutrient medium in sterile conditions.
1
Small pieces called explants are cut from the plant that is to be cloned.
2
The surfaces of the explants are sterilised with disinfectant and rinsed in sterile water.
3
Each explant is placed on sterile nutrient agar in a Petri dish, where its cells divide to form a callus.
4
The callus is moved to a fresh medium containing plant growth regulators, which makes it develop roots, stems and leaves.
5
The small plants, called plantlets, are transferred to potting trays and grow into mature plants.
Section 2 of 4Advantages
Growers use micropropagation to produce large numbers of reliable plants.
Advantages
Genetically identical
- All of the plants are clones, so desirable features of the parent, such as disease resistance, are kept.
Fast and cheap
- Many plants can be made in a small space, and they grow into mature plants faster than seedlings do.
All year round
- Production in the laboratory does not depend on the seasons.
Conservation
- Rare plant species that make few seeds can be propagated to protect them from extinction.
Section 3 of 4Disadvantages
Disadvantages
Skilled staff
- Trained workers and a sterile laboratory are needed, which adds to the cost.
No variation
- Clones share the same genes, so one disease or pest may affect all of the plants.
Less adaptable
- With no genetic variation, the population cannot adapt easily to a changing environment.
Risk of infection
- If microbes enter a culture, a whole batch of plantlets may be lost.
Section 4 of 4Exam Checklist & Tips
4.4.1 – Key Points for the Exam
- Micropropagation Production of many genetically identical plants from small pieces of tissue grown on a medium.
- Clone An organism that is genetically identical to its parent.
- Explant A small piece of plant tissue used to start a culture.
- Callus A mass of undifferentiated cells.
- Plant growth regulators Hormones in the medium that make the callus develop roots and shoots.
Common Mistakes
- Leaving out the sterilisation of the explants, which is needed to stop microbes growing on the agar.
- Saying that the plants made are genetically different from the parent, when they are clones.
- Describing the callus as having roots and leaves already, when it is an undifferentiated mass of cells.
- Listing only advantages, when a lack of genetic variation is an important disadvantage.