part 2: understanding plant growth in vitro richard r williams
TRANSCRIPT
Part 2:Understanding Plant
Growth In Vitro
Richard R Williams
1. Fundamental Concepts / History
2. Types of Cells or Tissues
3. Cell to Cell Interaction
4. Growth Processes
Topics to be covered:
“… the aseptic culture of plant protoplasts, cells, tissues or organs under conditions which lead to cell multiplication or regeneration of organs or whole plants “
What is Plant Tissue Culture?
Cell theory and totipotency
Callus formation and growth substances
Early cell culture
First plant tissue cultures
Animal tissue cultures
Plant organ culture
1 History
Cork tissue as observed by Robert Hooke in 1664
Cell theory ….
Totipotency ….
… each living cell has a complete genetic blueprint and therefore has the potential to develop into an entire plant.
… 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
… complete genetic blue print
… cells differentiate
… living plant cells can re-differentiate
Callus Formation ….…
…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 Cell Culture ….
Cell enlargement … role of auxins
Cell division ... role of cytokinins
- dependent on discovery of “growth regulators”
Early tissue culture ….
Regeneration from tobacco pith ..
(Skoog and Miller) … interaction of auxin
and cytokinin gives differentiation.
GA for growth of shoots
Aux + Cyt + sucrose > vascular development
Culture of ‘thin layers’ … many interacting factors eg pH
Further development …
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
Many different types of cells
Varying degrees of specialisation
- Meristematic- Embryonic- Reproductive
2 Types of Cell & Tissues
Shoot ... apical, … axillary
Meristematic tissues ...
leaf trace
procambium
tunicanew leaf
corpus
pithcortex
apical meristem
axillary meristem
Shoot ... apical, … axillary
Leaf
Root
Meristematic tissues ...
Shoot ... apical, … axillary
Leaf
Root
Adventitious
Cambial tissues
Meristematic 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
Important in intact plant
Isolated cell not function the same
Establishment of polarity
Expression of somaclonal (epigenetic)
variation
3 Cell to Cell Interaction
Multiplication Apical dominance Differentiation
Growth Cell division Cell enlargement
Phasic development Juvenility Dormancy
4 Growth Processes
Photosynthesis
Transpiration and water uptake
Cytological instability
4 Other Processes
Physiological mechanisms Physical manipulation Chemical Plant Growth Regulators
(PGRs)
Environment
Genotype
5 Controlling Growth & Development
Hormone theory Auxins Cytokinins
Gibberelins (GA) Ethylene Abscisic Acid (ABA)
Other PGRs
6 Growth Regulators
Hormone BalanceAuxin Cytokinin
High Low
Low High
Root formation on cuttings Embryogenesis
Adventitious root formation in callus Callus initiation
Adventitious shoot formation Axillary shoot growth
Auxin : Cytokinin ratio
Hormone Action …..
Application + uptake
Endogenous + applied
Accumulation & Habituation
Interactions / Sequence
Pulsing vs prolonged exposure
END of Part 2