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Auxins and cell elongation

Wall growth
by

Anna Bailach

on 7 November 2013

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Transcript of Auxins and cell elongation

AUXINS AND CELL ELONGATION
Introduction
Cell Growth
How auxin promotes cell elongation

Concept of hormone
The normal development of a plant needs
external
and
internal
factors.
First definiton of hormone (animal physiology )
Phytohormones
They are
organic
substances, generally crystallized
Regulate correlative processes
Are very
specific
Are
pleiotropics
Auxins
Chemical composition
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
Proton pumping
- Direct activation
- Enhanced synthesis of plasma H+-ATPase

Acidification process
Gene regulation
Transcription regulation by ARFs.

Steps and parameters
What is growth?
Cell cycle
Auxin effect
Elongation
Cell division (not necessarily)
Cell wall components
Cell wall rigidity
Determines growth
Polysaccharides
Cross-linking glycanes
Pectin matrix polymers
Structural proteins

Multinet growth hypothesis
GR = m (ΔѰP -ϒ)
light, nutrients, water, temperature
hormones
"substance synthesized in secretory glands and transported where is needed by the specific physiological processes"
Organ
Stimuli
Response
amplification
translation
Vegetal hormones control a big amount of
processes
:
plant growth
falling of leaves
blooming
fruit development
germination

We have 5 main groups
auxines
giberelines
citoquinines
ethilene
abcisic acid

Proton extrusion and gene regulation
Auxin action: Acidification
H+-ATP-ases and proton extrusion
Auxin action:
Gene regulation
Besides acidifying, long term growth
.
Extensibility coefficient, which is what auxins alter
Postulates that auxin-dependent acidification of the cell wall promotes wall extensibility.

Expansins
Acid growth hypothesis

Cyclin D
CDK
fosforilations
Conclusion
Acidification
Plasticity
Cell elongation
Gene regulation
Indol-3-acetic Acid

Natural and Synthetic
Indol acetic nitrile
indol-acetic-amide
Natural
Synthetic

Place of synthesis
Effects
Auxins can be found all along the plant
high concentrations in
meristematic
tissues
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
• Tropisms
• Diferentitation of vascular tissues
• Stimulates cambium activity
• Stimulates falling of leaves and blooming
• Stimulates fruit development

Other tissues

- Auxin enters nucleus. TIR1.
- Attachment of ubiquitin to Aux/IAA proteins.
- Proteasome destruction of the latter.
- ARFs stop being inhibited.
- Gene transcription
Process
New proteins and polysaccharides
=
Continued cell growth
Weed killers
BIBLIOGRAPHY

https://www.boundless.com/biology/cellular-signaling-in-plants/auxins/auxins-control-cell-elongation/
http://www.plant-hormones.info/auxins.htm
http://passel.unl.edu/pages/informationmodule.php?idinformationmodule=998688536&topicorder=6&maxto=11
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1080619/
http://bcs.whfreeman.com/thelifewire/content/chp38/3802003.html
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/A/Auxin.html
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.
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