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Background Information The first plant hormone discovered by Frits Went in 1926 The most intensely studied molecule in plants Involved in almost every aspect of plant growth, such as cell division and specialization Crucial for the correct foundation of root growth IAA (indole-3-acetic acid) is a form of Auxin One of the most prevalent and important forms of Auxin
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SANDY ALKOUTAMI, RACHEL GUENTER, WILL BANISH, AND TAYLOR BLACK
Auxin
Molecular Formula
C10H9NO2
Background Information
The first plant hormone discovered by Frits Went in 1926
The most intensely studied molecule in plantsInvolved in almost every aspect of plant
growth, such as cell division and specialization
Crucial for the correct foundation of root growth
IAA (indole-3-acetic acid) is a form of AuxinOne of the most prevalent and important
forms of Auxin
Origin in Plants
Auxin synthesis occurs in shoot apical meristem and young leaves
Produced in root apical meristemsGrowing fruits and seeds contain high
amounts of AuxinHowever, it is still uncertain whether Auxin is
produced of transported from maternal tissues
Destination
Auxin is typically produced in shoot tipsTransported between cells down the stem of
a plant (1 cm/hr)Auxin moves from tip to base; never in the
opposite direction Polar transport
Polar transport in auxin results from the polar distribution of its transport proteins in cells
Functions of Auxin
Promotes the production of lateral and adventitious roots
Controls the development of fruitEnhances apical dominancePromotes vascular differentiation Retards leaf abscissionStimulates stem elongationInvolved in phototropism
Phototropism
Phototropism is the growth of a shoot toward or away from light
The shoot tip, which contains auxin, is responsible for the direction in which the shoot moves
The areas where the sun hits the shoot has the least amount of auxin; however, the shaded areas of the shoot have the most
The auxin in these areas respond to the lack of light by controlling the movement of the shoot towards the sun
Cell Elongation
Auxin stimulates cell growth by binding to a receptor in the cell membrane
Acid growth hypothesis is a model reflecting this process
In the shoot’s region of elongation, auxin promotes the cell membrane’s proton pumps Increases voltage across the membrane and lowers pH in cell
wallThe increasing membrane potential promotes the
uptake of ions in the cell Enables osmosis which increases turgor Increased turgor allow the cell to elongate
Flowchart
Transduction• A second messenger
activates DNA binding protein which goes to the golgi and also activates an ATP synthase
• Next step: auxin regulated gene in the nucleus
Response• Growth proteins
are synthesized
Sources
http://www.cshperspectives.cshlp.org/content/2/10/a004572.full http://www.plant-hormones.info/auxins.htm http://pubs.acs.org/cen/news/83/i22/8322notw1.html https://docs.google.com/viewer?a=v&q=cache:pt4NiTdCOlQJ:classes.uleth.ca/
200603/biol4560a/xu.pdf+background+information+of+auxin&hl=en&gl=us&pid=bl&srcid=ADGEESj-Yw-8ggInhDRbOk8ZpgYJqnH2dvrjqXBntJy-poWnOnL1Gy19FYLqznEuNzMjbvA9QFFt3LLUdpTa0ad-86G8yQ9nLDt4F9RS3pDU0ZL4D2LDjzpdzD4d4eyVRi_2RGwDLAF0&sig=AHIEtbRKW1qcyKDEq1ycfIqHz2dI8VqXdw
http://auxin.hawaii-conference.com/sponsors https://docs.google.com/viewer?
a=v&q=cache:pteaMyuZlPYJ:rhsapbiology.wikispaces.com/file/view/Ch%255B1%255D.%2B39%2BPlant%2BResponses%2Bto%2BInternal%2Band%2BExternal%2BStimuli.ppt+&hl=en&gl=us&pid=bl&srcid=ADGEESgaZcxAeyYpEIwNimuEk2_K2q8t7P7tNtB_FA5FnBP51JDonk-FA2Eu_KMigKY-hW0M15j3i6nrjJpJkg1wDKFd0J4f_gLMoWGY4hKVfP0mSQURlWVEGX7OqvReenXlwgHRYN3B&sig=AHIEtbRrI6b6OzvZddRRwOWhSdFsDR0BaA
Campbell NA, Reece JB. 2011. Biology 9th ed. San Francisco (CA): Pearson/Benjamin Cummings