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 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 tunica new leaf corpus pith cortex 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 l Apical dominance l Differentiation \ Growth l Cell division l Cell enlargement \ Phasic development l Juvenility l 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 Balance AuxinCytokinin HighLow 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