Propagating Plants by Tissue Culture

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Lesson 6

• Propagating Plants by Tissue Culture

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Next Generation Science/Common Core Standards
Addressed!

• HS-LS1-1. Construct an explanation based on
  evidence for how the structure of DNA determines
  the structure of proteins which carry out the
  essential functions of life through systems of
  specialized cells. Assessment Boundary
  Assessment does not include identification of
  specific cell or tissue types, whole body
  systems, specific protein structures and
  functions, or the biochemistry of protein
  synthesis.
• HS-LS2-5. Develop a model to illustrate the role
  of photosynthesis and cellular respiration in the
  cycling of carbon among the biosphere,
  atmosphere, hydrosphere, and geosphere.
  Clarification Statement Examples of models
  could include simulations and mathematical
  models.
• Assessment Boundary Assessment does not
  include the specific chemical steps of
  photosynthesis and respiration.

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Bell Work!

• 1. Discuss the importance of tissue culture
• 2. Discuss a tissue culture method of
  propagation used in the greenhouse industry
• 3. Where can tissue culture be applied in the
  commercial field of agriculture?
• 4. Discuss what type of plants are best suited
  for tissue culture propagation

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Terms

• Auxins
• Callus
• Cytokinins
• Explants
• Plantlet
• Sterile agar medium
• Sterile technique
• Tissue culture

• Cultivar
• Resistance
• Explants

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Interest Approach

• Weve talked about how you can produce African
  violets through leaf cuttings.
• But, what if you had to produce 1,000 of them
  that are identical to each other in a short
  period of time?
• What problems/challenges would this produce for
  the grower?
• How can tissue culture help solve this problem?

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What Is Tissue Culture and Why Is It Important?

• Tissue culture is the practice of growing plant
  cells on artificial media
• It involves the culture or growing of small
  pieces of plant tissue
• It is performed on artificial medium under
  sterile conditions
• Foliage plants, pot plants and cut flowers are
  propagated by this method

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Advantages of Tissue Culture

• 1. Large numbers of plants can be produced from a
  single plant in relatively small space in a short
  period of time
• This reduces growing space, labor and plant
  maintenance requirements

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Advantages Continued

• 2. Viruses and other systemic diseases are
  eliminated by propagating the quickly dividing
  cells of the shoot tip
• 3. The grower is able to produce plants with
  identical flowers
• 4. Horticultural cultivars can be improved by
  selecting plants, which vary slightly from the
  mother plant
• Examples are leaf shape, disease resistance,
  growth habit and flower color
• 5. The growth of identically engineered plant
  cells

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What Process Is Used For Tissue Culture
Propagation?

• The tissue culture propagation process can be
  defined in four main stages
• A. First stage - small pieces of plant material,
  called explants, are carefully removed form the
  parent plant
• Explants are obtained from the actively growing
  part (shoot tips, sections of leaves, stems and
  roots, embryos, etc) of a desired plant

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• The explants are cleaned and placed on sterile
  agar medium in glass bottles or test tubes
• The sterile agar medium is a gel that contains
  water, sugars, nutrients, and plant hormones to
  support and promote plant growth
• Tiny leaves, stems and roots make tissue culture
  possible

Removing explants
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• B. Stage two - the cells of the explants
  multiply in one of two ways
• 1. The cells may form a callus, which is a group
  of cells with no particular function
• Supplied with the correct hormones in the medium,
  these callus cells can develop into a normal
  plant
• 2. The explant may produce many new explants if
  cytokinins, hormones responsible for cell
  division and differentiation, are placed in the
  medium

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Stage Two Explant Multiplication
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• Cytokinins encourage the increase in the number
  of buds on the explants to six or more per shoot
• Each bud is capable of becoming a plant and
  producing more buds
• Branching occurs as these buds develop into plant
  shoots, or plantlets
• These plantlets are divided and transferred to
  new containers
• In this way, a single explant can produce
  millions of plantlets in a year

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• D. Stage four - the plantlets are removed form
  the glass container
• C. Stage three - the plantlets have developed
  and are ready for root formation
• Shoots are transplanted to another medium
  containing auxins, a hormone that induces the
  growth of roots
• The plantlets are also given higher light
  intensity in preparation for stage four

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• They are divided, planted in a sterile medium,
  and placed in a greenhouse
• Care must be taken during this transition to
  acclimatize the plant to their new environment

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Tissue Culture Process Continued

• One of the most important aspects of tissue
  culture is sterile technique
• Sterile technique is the maintenance of an
  environment that is free of bacteria, fungi and
  viruses
• Sterilization of the agar media is essential
• In addition, the slightest air movement can stir
  spores of bacteria and fungi

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• Special sterile work stations, called laminar
  hoods, are used when possible

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• Cleaning of the plant before removal of the
  explant is usually accomplished by a brief
  soaking in a bleach solution, followed by a rinse
  in sterile water
• The tissue culture agar medium and other
  materials used to prepare and place the explant
  must be sterilized
• This is usually done by an autoclave

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• The autoclave uses pressurized steam to sterilize
  medium, glassware, and instruments

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• Cultures are transferred from one container to
  another at various stages in their development
• This transfer must occur under sterile conditions
  to prevent contamination by microorganisms
• Sterilized equipment must be used for each
  transfer

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Summary

• Why is tissue culture important in the
  horticulture industry?
• What parts of a plant can be used in tissue
  culture?
• Define explant.
• Give two advantages for using tissue culture.
• What is a sterile agar medium?
• What is the first stage in the tissue culture
  propagation method?

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Summary Continued

• What is a callus?
• What must be added to a callus in order for it
  to continue to develop?
• What is a plantlet?
• How do auxins help an explant?
• What are some practices of sterile technique?

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The End!