1. Asexual Reproduction in Plants
Vegetative Propagation

2. Contents Definition Modified Stems Modified Roots Modified Leaves
Modified Buds
Sexual Vs Asexual Reproduction
Vegetative Propagation
Cuttings
Grafting
Layering
Budding
Micropropagation (Tissue Culture)
Cloning

3. Definition
asexual reproduction: does not involve the manufacture or union of sex cells or gametes
e.g. binary fission, fragmentation, spore formation and budding
- involves only one parent and offspring are genetically identical (have the same genetic content) to parent.

4. What happens?
Part of the plant becomes separated from the parent plant and grows into a new plant.
New plants generally develop from an axillary bud of the parent plant.
Parts of the parent plant are specially modified for the purpose.

5. Modified Stems
Runners: horizontal running over the soil surface - terminal bud of the runner sends up new shoots e.g. strawberry, creeping buttercup.
Stem Tubers: swollen underground stem tip - buds (eyes) produce new shoots e.g. potato

6. Runners e.g. strawberries

7. Stem tubers e.g. potatoes

8. Modified Roots
Root Tuber: swollen fibrous roots — no eyes (buds) e.g. dahlia, lesser celandine
Note:
Tap Root: swollen roots for food storage - not a reproductive organ - biennial plants e.g. carrot, turnip

9. Root tuber e.g. dahlia

10. Modified Leaves
Some plants produce plantlets along the edges of the leaves.
Plantlets reach a certain size, fall off and grow into new plants e.g. Bryophyllum (mother of thousands)

11. Bryophyllum with plantlets

12. Modified Buds
Bulbs: swollen underground bud with fleshy leaves and reduced stem e.g. daffodil, onion, tulip

13. An onion bulb

14. Bulb – swollen leaves on a flat stem

15. Sexual (Seed) Vs Asexual (Vegetative) Reproduction (1/2)
Cross pollination ensures variation
More resistant to disease.
Dispersal reduces competition.
Seeds can remain dormant and survive unfavourable conditions
Sexual reproduction favours evolution
Sure of establishing new daughter plant
New plants well developed before separating from parent
Retain parental genotype.
New plants obtained in a shorter time.
Only one parent needed.

16. Sexual Vs Asexual Reproduction (2/2)
Seed production - complex.
A lot of seed produced - few new plants obtained.
Pollination + dispersal depend on external agents.
Seeds + fruits eaten by animals
Grow in clumps - competition for minerals, light, space.
Susceptible to disease - all genetically similar - clones

17. Vegetative propagation
vegetative propagation: reproduction not involving seed
Two types:
Natural e.g. rhizomes, corms, tubers, bulbs,
Artificial - used by gardeners to propagate plants e.g. cuttings, layering, grafting, and budding.

18. Cuttings
cutting: slip removed from plant and rooted in water or well-watered compost e.g. busy lizzie, geranium.

19. Grafting
grafting: method of plant propagation where the scion (i.e. the plant to be propagated) is attached to the stock (i.e. the plant onto which it is grafted) e.g. apple trees.

20. Layering
layering: method of artificial / vegetative propagation where a branch of a plant is bent over and pinned to the earth at a node.
When roots develop the branch is separated from the parent plant.
Useful for the propagation of woody plants e.g. blackberry, gooseberry.

21. Budding
budding: a method of plant propagation where a bud (of a rose) is attached to the stock (of a briar) e.g. roses.

22. Micropropagation (Tissue Culture) (1/2)
Cells removed from a plant or animal and grown as a tissue culture in a special culture medium.
An entire plant can be grown from a small piece of stem, leaf or root tissue.
Once the tissue develops into a plantlet it can be divided up again to produce many identical plants.
Used in mass production of house plants and crops such as bananas, strawberries and oil palm trees.

23. Micropropagation (Tissue Culture) (2/2)
Provides a larger number of plants more quickly than cuttings.
Can be used to check cells for a particular feature e.g. resistance to chemicals or a particular disease.

24. Tissue culture in the laboratory

25. Micropropagation of oil palm trees

26. Cloning
clone: all offspring genetically identical - produced asexually i.e. all have come from one original parent e.g. King Edward potato.
Clones are produced by mitosis.
All the offspring from the various methods of vegetative reproduction (both natural and artificial) mentioned above are examples of clones.

27. END