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Auxins and cell elongation
Transcript of Auxins and cell elongation
How auxin promotes cell elongation
Concept of hormone
The normal development of a plant needs
First definiton of hormone (animal physiology )
substances, generally crystallized
Regulate correlative processes
Steps in which the cell expands
1. Osmotic uptake of water
2. Turgor pressure builds up
3. Biochemical wall loosening
Parameters of growth rate
1. dl/dt = Lp (Δψw ) quantifies length
2.dV/dt = A•Lp(Δψw) quantifies volume
ϒ is the yield threshold
How does auxin promote cell elongation?
How does acidifying the wall help cell growth?
How does auxin induce the acidification of the wall?
How does auxin relate to enzymes that participate in wall loosening?
What else do auxins do?
Acidification: Proton extrusion
- Direct activation
- Enhanced synthesis of plasma H+-ATPase
Transcription regulation by ARFs.
Steps and parameters
What is growth?
Cell division (not necessarily)
Cell wall components
Cell wall rigidity
Pectin matrix polymers
Multinet growth hypothesis
GR = m (ΔѰP -ϒ)
light, nutrients, water, temperature
"substance synthesized in secretory glands and transported where is needed by the specific physiological processes"
Vegetal hormones control a big amount of
falling of leaves
We have 5 main groups
Proton extrusion and gene regulation
Auxin action: Acidification
H+-ATP-ases and proton extrusion
Besides acidifying, long term growth
Extensibility coefficient, which is what auxins alter
Postulates that auxin-dependent acidification of the cell wall promotes wall extensibility.
Acid growth hypothesis
Natural and Synthetic
Indol acetic nitrile
Place of synthesis
Auxins can be found all along the plant
high concentrations in
They can be produced in vegetative tissues and transported to other parts of the plant
Auxins can move up from
the roots by using an opposite flow
• Expansion of coleoptiles and stems
• Apical dominance
• Diferentitation of vascular tissues
• Stimulates cambium activity
• Stimulates falling of leaves and blooming
• Stimulates fruit development
- Auxin enters nucleus. TIR1.
- Attachment of ubiquitin to Aux/IAA proteins.
- Proteasome destruction of the latter.
- ARFs stop being inhibited.
- Gene transcription
New proteins and polysaccharides
Continued cell growth
Azcón-Bieto, J., and Talón, M. Fundamentos de fisiología vegetal (2a ed.). MacGraw Hill.
Buchanan, Bob B., Gruissem, W., and Jones, R.L. (Eds). (2000). Biochemistry and molecular biology of plants. Maryland: Rockville.
Barceló Coll, J., Nicolás Rodrigo, G., Sabater GArcía, B. and Sánchez Tamés, R. (2001). Fisiología Vegetal. Madrid: Humanes de Madrid.
Davies, P.J. (Ed.). (1987). Plant Hormones and their role in Plant Growth and Development. The Netherlands: Dordrecht.
Wilkins, M.B. (Ed.).(1985).Advanced Plant Physiology. Great Britain: Bath.