SANDY ALKOUTAMI, RACHEL GUENTER, WILL BANISH, AND TAYLOR BLACK Auxin

Molecular Formula C 10 H 9 NO 2

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

Origin in Plants Auxin synthesis occurs in shoot apical meristem and young leaves Produced in root apical meristems Growing fruits and seeds contain high amounts of Auxin However, it is still uncertain whether Auxin is produced of transported from maternal tissues

Destination Auxin is typically produced in shoot tips Transported 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 fruit Enhances apical dominance Promotes vascular differentiation Retards leaf abscission Stimulates stem elongation Involved 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 wall The 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 /biol4560a/xu.pdf+background+information+of+auxin&hl=en&gl=us&pid=bl& srcid=ADGEESj-Yw-8ggInhDRbOk8ZpgYJqnH2dvrjqXBntJy- poWnOnL1Gy19FYLqznEuNzMjbvA9QFFt3LLUdpTa0ad- 86G8yQ9nLDt4F9RS3pDU0ZL4D2LDjzpdzD4d4eyVRi_2RGwDLAF0&sig=AHIEtb RKW1qcyKDEq1ycfIqHz2dI8VqXdw ces.com/file/view/Ch%255B1%255D.%2B39%2BPlant%2BResponses%2Bto%2BInt ernal%2Band%2BExternal%2BStimuli.ppt+&hl=en&gl=us&pid=bl&srcid=ADGEES gaZcxAeyYpEIwNimuEk2_K2q8t7P7tNtB_FA5FnBP51JDonk-FA2Eu_KMigKY- hW0M15j3i6nrjJpJkg1wDKFd0J4f_gLMoWGY4hKVfP0mSQURlWVEGX7OqvRee nXlwgHRYN3B&sig=AHIEtbRrI6b6OzvZddRRwOWhSdFsDR0BaA Campbell NA, Reece JB Biology 9 th ed. San Francisco (CA): Pearson/Benjamin Cummings