Title: Clones in nature Homework: complete learning package 11 for Thursday F215 – module 2 Biotechnologies and gene technologies

Learning Outcomes Describe the production of natural clones in plants using the example of vegetative propagation in elm trees. Describe the production of artificial clones of plants from tissue culture. Discuss the advantages and disadvantages of plant cloning in agriculture.

Cloning Cloning is the production of genetically identical organisms In plants cloning can occur naturally by asexual reproduction. All cells are produced by mitosis from cells that were originally part of the parent plant All plants are genetically identical to the parent plant and each other.

Asexual reproduction Advantages Disadvantages Quick All offspring have the genetic information to enable them to survive in the environment Disadvantages No genetic variety Does not allow for natural selection Unable to adapt to environmental conditions.

Vegetative propagation Asexual reproduction in plants is known as vegetative propagation Examples Strawberry plants produce runners Potatoes form underground tubers Daffodils produce bulbs English Elm produces root suckers (basal sprouts)

Vegetative propagation in potatoes

English Elm The English Elm only reproduces by suckering The growth of new trees from the roots or meristem tissue in the trunks As all English Elms are genetically identical they are all susceptible to the fungus, Dutch elm disease

[4]

Task Complete textbook questions on page 153 Mark your answers using the mark scheme at the back of the book Extension: complete the stretch and challenge question

Artificial clones and agriculture

Artificial Vegetative propagation It is possible to artificially propagate valuable plants Taking cuttings – cut a section of stem between nodes, then treat with plant hormones to encourage root growth Grafting – a shoot section of a woody stem is joined to a root stock Tissue culture

Cuttings A node is a region of growth on a plant. These small bumps can be seen where braches and leaves come off. Cuttings are taken beneath the node and the cutting is dipped in rooting powder, containing synthetic growth hormones e.g. auxins to stimulate root growth

Grafting

Tissue Culture Tissue culture allows for the production of huge numbers of genetically identical plants from a small amount of plant material. All stages in tissue culture must be carried out in sterile conditions to prevent fungal infection

Stages in Plant Tissue Culture A group of cells are removed from the parent plant called the explant. Explant is placed on a nutrient growth medium Cells divide to form a mass of undifferentiated cells called a callus Single cells removed from callus and placed on a growth medium to stimulate shoot growth The shoots are placed on a growth medium to stimulate root growth Growing plants transferred to a greenhouse before planting outside

Plant Cloning in Agriculture Desirable parent plant can be chosen and cloned Plants mature at same time In UK, Annual crops are propagated by seed After years of inbreeding all crops are now genetically uniform Even though seeds require sexual reproduction, all seeds and plants produced are genetically uniform

Plant Cloning in Agriculture In perennial plants, the high cost of vegetative propagation is offset by the long periods for which the plants stay in the ground Relatively high value of the product Examples Lavender Apple trees

Disadvantages of plant cloning Susceptible to disease Unable to adapt to climate change Loss of genetic variation

[7]