Chapter 27: Vegetative propagation

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Chapter 27 Vegetative propagation

• Leaving Certificate Biology
• Higher Level

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Asexual Reproduction

• Asexual reproduction is the making of a new
  independent organism from one parent
• Plants can reproduce asexually when conditions
  for sexual reproduction are unsuitable
• Plants reproduce asexually by 4 main ways
• Stem
• Root
• Leaf
• Bud

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Vegetative Propagation Stem

• Stem
• Stems can grow to form a new plant
• E.g. Strawberry runners
• Runners are stems that run horizontally across
  the surface of the soil
• The runners then form a node whereby the stem
  sends out a root and a shoot producing a new
  plant
• The new plant is genetically identical to parent

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Vegetative Propagation Root

• Root
• Certain plants form an underground root tuber
• Tubers remain dormant over winter thereby
  enabling plant to survive winter
• When conditions improve in spring, new shoots
  emerge from the buds on the tuber
• E.g. Dahlia

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Vegetative Propagation Leaf

• Leaf
• Some plants (e.g. Kalanchoe) can form completely
  new independent plants from outgrowths on their
  leaves
• Kalanchoe forms new plantlets on the edges of
  their leaves which then fall off to produce new
  plants

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Vegetative Propagation Bud

• Bud
• Vegetative propagation by buds involves the
  formation of a bulb underground
• A bulb consists of a section of underground stem,
  swollen leaves and a central apical bud aswell as
  lateral buds
• When conditions improve the apical and lateral
  bud form new shoots (this is why many daffodils
  form from one bulb)

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Comparison of Reproduction by Seed and
Reproduction by Vegetative Propagation

• Reproduction by seed
• Advantages
• Variation amongst offspring
• Wide dispersal (less competition)
• Some may resist disease
• Can remain dormant for years
• Disadvantages
• Complex
• Inefficient
• Slow

• Reproduction by Vegetative propagation
• Advantages
• Simple process
• Efficient
• Many offspring can be produced in short period of
  time
• Disadvantages
• Lack of variation
• Overcrowding in local habitat
• No seeds formed

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Artificial Propagation

• Artificial propagation is used by horticulturists
  to grow new plants and improve upon existing
  ones
• Cutting e.g. busy Lizzy, geranium
• Grafting e.g. roses, apple trees
• Layering e.g. blackberry bushes
• Micropropagation (tissue culturing) can be used
  to produce a plant of interest in the laboratory

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Artificial Vegetative Propagation Cutting

• Cutting
• Plants that can be artificially propagated
  include the busy Lizzie and geranium
• A cutting is removed from plant and transplanted
  to special soil that includes rooting powder

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Artificial Vegetative Propagation Grafting

• Grafting
• Grafting two plants together is used to combine
  the best qualities of two different plants
• e.g. roses and apple trees are example of plants
  in which grafting improves the quality of the
  roses and apples
• The part of one plant, the scion (shoot system),
  is removed and attached to the healthy part of
  another plant, the stock (usually a wild plant
  with a strong root system)

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Artificial Vegetative Propagation Layering

• Layering
• Layering involves taking a long branch of the
  parent plant and bending it down so that part of
  the branch is under the soil
• e.g. blackberry plants, roses and carnations are
  commonly layered to produce more plants with
  those desired characteristics, i.e. large flowers

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Artificial Vegetative Propagation
Micropropagation

• Micropropagation
• Micropropagation is tissue culturing of small
  amounts of plant tissue to produce new plantlets
  with the desired characteristics of the parent
  plant
• It is an expensive method of propagation but can
  be very efficient when huge numbers of the
  particular plant are required