Chapter 20: MOA Part 5 – Seedling Root Growth Inhibitors
20.5 Summary
This chapter discussed Seedling Root Growth Inhibitors. This class of herbicides interferes with a protein that is important in building microtubule protein fibers, which are needed to make spindle fibers. When these are disrupted, cell division is unable to take place. The physical symptoms seen in plants sensitive to this class are malformed roots and drought or nutrient deficiency symptoms due to the reduced root functions.
As an overall summary of all the Modes of Action explored in this book, recall that in general, herbicides do one of the following to interfere with normal plant biochemical processes:
- Shut down an enzyme
- Create free radicles that are toxic to plant
- Interfere directly with a biochemical process, like with spindle fiber formation
The Mode of Action chapters reviewed the status of herbicide resistant weed populations and provided a quick summary of how to slow or prevent resistance from becoming a problem in your own field.
Key Takeaways
Key takeaways from this chapter include:
- Tubulin is a protein that makes up microtubules and spindle fibers.
- Microtubules and spindle fibers are important to the cell division process.
- Seedling Root Growth Inhibitors, which have the microtubule inhibitor site of action herbicides, target the tubulin protein and effect rapidly dividing plant tissues the most (ie meristematic).
- Symptoms of microtubule inhibitors include fewer, shortened roots with swollen tips, swollen and brittle hypocotyls, and short, thick leaves that are purple in color. Plants may also appear drought stressed.
- 6 weed species in the US are resistant to microtubule inhibitors.
- 12 weed species globally are resistant to microtubule inhibitors.
- Creating Integrated Weed Management (IWM) plans that incorporate a combination of cultural practices, mechanical control methods and chemical control tools will help lower selection pressures and reduce challenges from herbicide resistant weeds.