Part 2: Understanding Plant Growth In Vitro

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Part 2Understanding Plant Growth In Vitro
Richard R Williams
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Topics to be covered

1. Fundamental Concepts / History
2. Types of Cells or Tissues
3. Cell to Cell Interaction
4. Growth Processes

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What is Plant Tissue Culture?

• the aseptic culture of plant protoplasts,
  cells, tissues or organs under conditions which
  lead to cell multiplication or regeneration of
  organs or whole plants

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1 History

• Cell theory and totipotency
• Callus formation and growth substances
• Early cell culture
• First plant tissue cultures
• Animal tissue cultures
• Plant organ culture

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Cell theory .
Cork tissue as observed by Robert Hooke in 1664
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Totipotency . each living cell has a complete
genetic blueprint and therefore has the potential
to develop into an entire plant.
complete genetic blue print
cells differentiate
cells lines differentiate to form specialised
tissues and organs
unlike animal cells, living plant cells can
de-differentiate and then re-differentiate to
form different cell types
living plant cells can re-differentiate
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Callus Formation .
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Early Cell Culture .
Haberlandt .. early 1900s proposed concept
of totipotency cells cultured under right
conditions
Callus cultured from tree cambium (Gautheret,
Nobecourt, Whire in the 1930s. cells
kept alive but did not develop
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Early tissue culture .
- dependent on discovery of
growth regulators

• Cell enlargement role of auxins
• Cell division ... role of cytokinins

• Regeneration from tobacco pith .. (Skoog and
  Miller) interaction of auxin and cytokinin
  gives differentiation.

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Further development

• GA for growth of shoots
• Aux Cyt sucrose gt vascular
  development
• Culture of thin layers many interacting
  factors eg pH

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Carrot plants from root cells Stewart in 1964
Steeves Sussex 1972
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Tobacco plants from single cells Vasil
Hilderbrandt 1965
Steeves Sussex 1972
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Plant Organ Culture .Murashige and Skoog 1962
- mineral media ? micropropagation
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2 Types of Cell Tissues

• Many different types of cells
• Varying degrees of specialisation

- Meristematic - Embryonic - Reproductive
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Meristematic tissues ...

• Shoot ... apical, axillary

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apical meristem
leaf trace
axillary meristem
procambium
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Meristematic tissues ...

• Shoot ... apical, axillary

• Leaf

• Root

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Meristematic tissues ...

• Shoot ... apical, axillary

• Leaf

• Root

• Adventitious

• Cambial tissues

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Embryonic tissues ...

• Pre-formed plant
• Generative / somatic
• Juvenile

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Reproductive tissues ...

• Diploid / Haploid
• Female / Male

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Monocots versus Dicots

• Stems are leaf bases not buds
• Shoot apex at base
• Intercallary leaf growth

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3 Cell to Cell Interaction

• Important in intact plant
• Isolated cell not function the same
• Establishment of polarity
• Expression of somaclonal (epigenetic)
  variation

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4 Growth Processes

• Multiplication
• Apical dominance
• Differentiation
• Growth
• Cell division
• Cell enlargement
• Phasic development
• Juvenility
• Dormancy

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4 Other Processes

• Photosynthesis
• Transpiration and water uptake
• Cytological instability

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5 Controlling Growth Development

• Physiological mechanisms
• Physical manipulation
• Chemical Plant Growth Regulators (PGRs)
• Environment
• Genotype

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6 Growth Regulators

• Hormone theory
• Auxins
• Cytokinins
• Gibberelins (GA)
• Ethylene
• Abscisic Acid (ABA)
• Other PGRs

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• Hormone Balance
• Auxin Cytokinin
• High Low
• Low High

• Root formation on cuttings
• Embryogenesis
• Adventitious root formation in callus
• Callus initiation
• Adventitious shoot formation
• Axillary shoot growth

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Auxin Cytokinin ratio
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Hormone Action ..

• Application uptake
• Endogenous applied
• Accumulation Habituation
• Interactions / Sequence
• Pulsing vs prolonged exposure

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END of Part 2