By the end of this lesson
- Explain why micropropagated plants are genetically identical.
- Describe commercial uses of micropropagation.
- Evaluate the advantages and disadvantages of producing clones.
BIG QUESTION
Why might a nursery clone its best orchid rather than grow it from seed?
Seeds produce variable offspring; clones keep exactly the characteristics customers want.
Why the plants are identical
All cells in the new plants come from the parent by mitosisCell division that produces two genetically identical diploid cells, for growth, repair and asexual reproduction., so every plant is a cloneAn organism or cell that is genetically identical to its parent; cloning is producing such copies.: genetically identicalHaving exactly the same genes, as clones produced by asexual reproduction do. to the parent and each other.
If the parent has a desirable characteristic, such as flower colour or disease resistance, every clone inherits it.
Commercial quantities
One parent can provide many explants, and plantlets can be divided repeatedly, so large numbers of plants are produced quickly, all year round and in a small space.
Uses include ornamental plants such as orchids, rare or endangered plants, plants that are hard to grow from seed, and producing disease-free stock such as bananas or potatoes.
Disadvantages
Because the clones have no genetic variationDifferences between individuals of the same species caused by differences in their alleles., a new disease or change in conditions could affect all of them.
Laboratory set-up, sterile technique and skilled staff can be expensive, and contamination can lose a whole batch. Whether it is worthwhile depends on the value of the plant.
Growing from seed or micropropagation
Compare the outcomes for a commercial grower.
| Feature | Growing from seed | Micropropagation |
|---|---|---|
| Genetic variation | Offspring vary. | Genetically identical clones. |
| Speed and number | Depends on seed production and season. | Very many plants quickly, all year. |
| Cost | Usually cheaper. | Expensive laboratory and skills. |
Language that earns precision
- clone
- An organism genetically identical to its parent.
- genetically identical
- Having exactly the same DNA.
- commercial quantities
- Numbers large enough to sell profitably.
Common misconceptions
Claim: Clones are always better plants.
Correction: They are only as good as the parent and share its weaknesses.
Claim: Clones of a parent can look different because of their genes.
Correction: Any differences are due to the environment, not genes.
Claim: Micropropagation creates new desirable characteristics.
Correction: It copies characteristics the parent already has.
Match the answer to the command word
Use mitosis → genetically identical → keeps desirable characteristics.
Include speed, numbers and uniformity against cost and lack of variation.
Recall, apply, then justify
Explain why all plants produced by micropropagation from one parent have the same desirable characteristics.
Hint
Type of cell division.
Suggested marking points
- Cells are produced by mitosis.
- So the plants are genetically identical (clones) to the parent.
Give two advantages of micropropagation for a commercial grower.
Hint
Number and time.
Suggested marking points
- Large numbers of plants produced quickly / from a small amount of tissue.
- Plants are uniform / all have the desirable characteristic, or can be grown all year in a small space.
Evaluate the use of micropropagation to produce all the banana plants on a large plantation.
Planning hint
Uniformity is both strength and weakness.
What a strong design includes
- Large numbers of plants can be produced quickly.
- All plants have the desired characteristics, such as high yield.
- Disease-free stock can be produced.
- Uniform plants make harvesting and marketing easier.
- No genetic variation means one disease could destroy all the plants.
- Costs are high, so it may only be worthwhile for valuable crops.