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