17.2 Importance of Auxin

Deana Namuth-Covert; Amy Kohmetscher

Chapter 17: MOA Part 3: Growth Regulators (Auxinic Herbicides)

17.2 Importance of Auxin

The term “auxin” is from the Greek word, auxein, meaning ’to increase’ and was first used by Frits Went in 1926 to describe the natural plant hormone, indole-3-acetic acid (IAA), which is the compound that caused curvature of oat coleoptiles.

The following YouTube video describes IAA’s important role in plant growth, including how it causes plants to grow towards the sun and its effects on root growth.

</p> <p>Synthetic auxins are herbicide chemicals that look very similar to the plant’s IAA. There is one herbicide Mode of Action with two Sites of Action that negatively affect plants by mimicking an overdose of auxin. The second SOA class inhibits how plant auxin is moved into cells.</p> <p>Growth Regulators</p> <ul> <li>Group 4. Synthetic Auxins (SA) (HRAC Group O)</li> <li>Group 19. Auxin Transport Inhibitors (ATI) (HRAC Group P)</li> </ul> <figure id="attachment_1251" aria-describedby="caption-attachment-1251" style="width: 400px" class="wp-caption aligncenter"><a href="https://ohiostate.pressbooks.pub/app/uploads/sites/162/2018/10/MOA-schematic.jpg" target="_blank" rel="noopener"><img fetchpriority="high" decoding="async" class="wp-image-1251" src="https://ohiostate.pressbooks.pub/app/uploads/sites/162/2018/10/MOA-schematic.jpg" alt="diagram of a cell indicating which cellular processes are impacted by herbicide classes" width="400" height="300" srcset="https://ohiostate.pressbooks.pub/app/uploads/sites/162/2018/10/MOA-schematic.jpg 960w, https://ohiostate.pressbooks.pub/app/uploads/sites/162/2018/10/MOA-schematic-300x225.jpg 300w, https://ohiostate.pressbooks.pub/app/uploads/sites/162/2018/10/MOA-schematic-768x576.jpg 768w, https://ohiostate.pressbooks.pub/app/uploads/sites/162/2018/10/MOA-schematic-65x49.jpg 65w, https://ohiostate.pressbooks.pub/app/uploads/sites/162/2018/10/MOA-schematic-225x169.jpg 225w, https://ohiostate.pressbooks.pub/app/uploads/sites/162/2018/10/MOA-schematic-350x263.jpg 350w" sizes="(max-width: 400px) 100vw, 400px" /></a><figcaption id="caption-attachment-1251" class="wp-caption-text">Figure 3. Cellular targets of herbicide action and herbicide classification by mode of action according to the Herbicide Resistance Action Committee (HRAC). Herbicides target only a few proteins or processes among the tremendous range present in plants. From: Deciphering the evolution of herbicide resistance in weeds. Christophe Delye et. al. 2013, Trends in Genetics. <a href="http://weedscience.com/summary/SOADescription.aspx" target="_blank" rel="noopener">http://weedscience.com/summary/SOADescription.aspx</a></figcaption></figure> <div class="textbox textbox--examples"> <header class="textbox__header"> <p class="textbox__title">Review and Reflection</p> </header> <div class="textbox__content"> <p style="text-align: center"> <div id="h5p-98"> <div class="h5p-iframe-wrapper"><iframe id="h5p-iframe-98" class="h5p-iframe" data-content-id="98" style="height:1px" src="about:blank" frameBorder="0" scrolling="no" title="Weeds_Ch17_AuxinImportant">

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