Transcript General - Jamyang

Part 2:
Understanding Plant
Growth In Vitro
Richard R Williams
Topics to be covered:
1. Fundamental Concepts / History
2. Types of Cells or Tissues
3. Cell to Cell Interaction
4. Growth Processes
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 “
1 History
 Cell theory and totipotency
 Callus formation and growth substances
 Early cell culture
 First plant tissue cultures
 Animal tissue cultures
 Plant organ culture
Cell theory ….
Cork tissue as observed by Robert Hooke in 1664
Totipotency ….
… each
livinggenetic
cell has
a complete
genetic
complete
blue
print
blueprint and therefore has the potential to
develop into an entire plant.
…cells
cellslines
differentiate
…
differentiate to form specialised
tissues and organs
unlikeplant
animal
cells,
plant cells can
… living
cells
canliving
re-differentiate
de-differentiate and then re-differentiate to
form different cell types
Callus Formation ….…
Early Cell Culture ….
…Haberlandt .. early 1900’s
… 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
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.
Further development …
 GA for growth of shoots
 Aux + Cyt + sucrose
> vascular development
 Culture of ‘thin layers’
… many interacting factors eg pH
Carrot plants from root cells – Stewart in 1964
[Steeves & Sussex 1972]
Tobacco plants from single cells
– Vasil & Hilderbrandt 1965
[Steeves & Sussex 1972]
Plant Organ Culture ….
Murashige and Skoog 1962 - mineral media
 micropropagation
2 Types of Cell & Tissues
Many different types of cells
Varying degrees of specialisation
- Meristematic
- Embryonic
- Reproductive
Meristematic tissues ...
Shoot ... apical,
… axillary
new leaf
tunica
apical
meristem
corpus
leaf trace
axillary
meristem
procambium
cortex
pith
Meristematic tissues ...
Shoot ... apical,
… axillary
Leaf
Root
Meristematic tissues ...
Shoot ... apical,
… axillary
Leaf
Root
Adventitious
Cambial tissues
Embryonic tissues ...
 Pre-formed plant
 Generative / somatic
 Juvenile
Reproductive tissues ...
 Diploid / Haploid
 Female / Male
Monocots versus Dicots
 ‘Stems’ are leaf bases … not buds
 Shoot apex at base
 Intercallary leaf growth
3 Cell to Cell Interaction
 Important in intact plant
 Isolated cell not function the same
 Establishment of polarity
 Expression of somaclonal (epigenetic)
variation
4 Growth Processes
 Multiplication

Apical dominance
 Differentiation
 Growth

Cell division
 Cell enlargement
 Phasic development

Juvenility
 Dormancy
4 Other Processes
 Photosynthesis
 Transpiration and water uptake
 Cytological instability
5 Controlling Growth
& Development
 Physiological mechanisms
 Physical manipulation
 Chemical Plant Growth Regulators
(PGRs)
 Environment
 Genotype
6 Growth Regulators
 Hormone theory
 Auxins
 Cytokinins
 Gibberelins (GA)
 Ethylene
 Abscisic Acid (ABA)
 Other PGRs
Hormone Balance
Auxin
High
Cytokinin
Low
Root formation on cuttings
Embryogenesis
Adventitious root formation in callus
Callus initiation
Adventitious shoot formation
Axillary shoot growth
Low
High
Auxin : Cytokinin ratio
Hormone Action …..
 Application + uptake
 Endogenous + applied
 Accumulation & Habituation
 Interactions / Sequence
 Pulsing vs prolonged exposure
END of Part 2