6.4.2(Clones in plants)

Name the methods of cloning plants

• Cuttings

• Tissue culture

• Micropropagation

Describe the process of taking cuttings to clone

• Use a healthy plant

• Cut stem at a slant between 2 lead joints(nodes)

• Dip cut end into rooting powder containing auxin to stimulate growth in root

• Place cut end into soil and water well

• Cover with plastic bag to reduce transpiration

• New roots will grow from stem tissues

Describe the disadvantages of cuttings

• Time consuming

• Cannot be done on a large scale

• Needs a lot of space

• Some plants do not respond well to cuttings

Describe what is meant by an explant

• Small pieces of plant tissue which contain meristematic tissue

Describe what is meant by a callus

• A mass of undifferentiated, totipotent cells

Describe the process of micropropagation

1. Suitable plant material is selected - explants

2. Explants are sterilised

3. Explants are placed on sterile growth medium containing plant hormones such as auxins and cytokines

4. These plant hormones stimulate mitosis and the explants form a callus

5. The callus is divided to produce a number of small clumps of undifferentiated cells

6. Small clumps grown on different growth media to encourage roots and then shoots

7. Tiny plantlets form and are transferred to a green house to be grown in compost or soil and acclimatised to normal growing conditions

Describe how growing small clumps on different growth media stimulates growth

• Each medium contains a different ratios of auxin and cytokinin.

Describe what is meant by horticulture

• The science and art of the development, sustainable production, marketing and use of high-value, intensively cultivated food and ornamental plants

Describe the advantages of artificial cloninng

• It is a rapid method compared to growing from seeds

• Can be carried out instead of sexual reproduction

• Plants selected will all be genetically identical to parent plant - same desirable characteristics

• If original plant has an unusual combination of characteristics due to selective breeding, then this combination can be retained without the risk of losing that combination through sexual reproduction

• New plants are all uniform in their phenotype, makes them easier to grow and harvest

• Using the meristem as an explant ensures the new plants are free from viruses

Describe the disadvantages of using artificial cloning

• Tissue culture is labour intensive

• Expensive to set up facilities to preform tissue culture

• Can fail due to microbial contamination

• All cloned offspring are genetically identical - susceptible to disease

• No genetic variation