Vegetative Propagation (LC 2026) (Leaving Cert Biology): Revision Notes

Vegetative Propagation

Natural Vegetative Propagation

New plants grow from parts of the parent plant, such as stems, roots, leaves, or buds.

1. Stems:

• Runners: Horizontal stems that grow above ground and produce new plants at their nodes.
• Example: Strawberries.

2. Roots:

• Tubers: Swollen underground roots that develop buds, which grow into new plants.
• Example: Dahlia tubers.

3. Leaves:

• Some plants can grow new plants from their leaves if they detach from the parent plant or produce small plantlets along their edges.
• Example: Mother of Thousands.

4. Buds:

• Bulbs: Modified buds that contain a central apical bud and lateral buds, which grow into new plants.
• Example: Onions.

Artificial Vegetative Propagation

Horticulturists and farmers use artificial methods to propagate plants with desirable traits.

1. Cuttings:

• A part of the plant (usually a shoot with leaves) is cut and planted to grow into a new plant.
• A growth promoter can be used to encourage root formation.

2. Layering:

• A shoot of the parent plant is bent and buried in soil, with the tip remaining above ground.
• Roots develop from the buried portion, and the new plant can be separated.
  • Example: Blackberries.

3. Grafting:

• Two plants are joined together to combine desirable traits:
  • The scion (the shoot of one plant) is attached to the stock (the rooted portion of another plant).
  • Example: Apple trees.

4. Micropropagation (Tissue Culture):

• Growth of plants from small tissue samples under sterile conditions on an artificial medium.
• Used to produce large numbers of genetically identical plants.

Comparison of Sexual and Asexual Reproduction

Feature	Asexual Reproduction (Vegetative Propagation)	Sexual Reproduction
Number of Parents	One	Two
Gametes Involved?	No	Yes
Meiosis and Fertilisation	No	Yes
Genetic Variation	None (clones)	Offspring are genetically varied
Speed	Fast	Slower
Resistance to Diseases	Less resistant	More resistant

Advantages and Disadvantages of Vegetative Propagation

Advantages:

1. Produces plants quickly.
2. Retains desirable traits (since offspring are clones).
3. Does not require external factors like pollinators.

Disadvantages:

1. No genetic variation, which can make plants more susceptible to diseases.
2. Lack of adaptability to environmental changes.