22.2 Artificial Cloning in Plants

Question 1

Definition of micropropagation

Answer 1

The process of making large numbers of genetically identical offspring from a single parent plant using tissue culture techniques

Question 2

When is micropropagation used?

Answer 2

When a desirable plant:
-Does not readily produce seeds
-Doesn’t respond well to natural cloning
-Is very rare
-Has been genetically modified or selectively bred with difficulty
-Is required to be ‘pathogen free’ by growers (eg. strawberries, bananas, potatoes)

Question 3

What are the stages of tissue culture?

Answer 3

1. A group of cells are removed from the explant (parent plant)
2. The explant is sterilised, usually by immersing it in sterilising agents (eg. ethanol, bleach, sodium dichloroisocyanurate)
3. The explant is placed on a sterile nutrient growth medium containing a balance of plant hormones (including auxin and cytokinins) which stimulate mitosis
4. The cells divide/proliferate to form a mass identical undifferentiated cells called a callus
5. The callus is divided up and individual cells or clumps are transferred to a new culture medium containing a mixture of different hormones and nutrients which stimulates the growth of tiny, genetically identical plantlets
6. The plantlets are potted into compost where they grow into small plants
7. The young plants are planted out to grown and produce a crop

Question 4

Why must tissue culture be carried out in sterile conditions?

Answer 4

To prevent fungal infection

Question 5

What sterilising agents could be used in tissue culture?

Answer 5

Ethanol, bleach, sodium dichloroisocyanurate

Question 6

What are the arguments for micropropagation?

Answer 6

-Rapid production of large numbers of plants with known genetic makeup which will yield good crops
-Culturing meristem tissue produces disease-free plants
-Makes it possible to produce viable numbers of plants after genetic modification of plant cells
-Producing large numbers of new plants which are seedless and therefore sterile to meet consumer tastes
-Way of growing plants which are naturally relatively infertile or difficult to grow from seed
-Way of reliably increase the number of rare or endangered plants

Question 7

What are the arguments against micropropagation?

Answer 7

-Produces monoculture, may plants genetically identical, all susceptible to the same disease or changes in growing conditions
-Expensive and requires skilled workers
-Explants and plantlets are vulnerable to infection like moulders during the process
-If the source material is infected with a virus, all the clones will be
-Can loose large numbers of new plants in the process