Originally published May 2007, updated April 2010
URL: http://www.kingcorn.org/news/timeless/FloppyCorn.html
"Rootless" or "Floppy" Corn Syndrome
R.L. (Bob) Nielsen
Agronomy Dept., Purdue Univ.
West Lafayette, IN 47907-2054
Email address: rnielsen
at purdue.edu
Seminal roots, but no upper nodal roots.
Click on an image to open a larger version.
xcessive drying of the upper soil profile is conducive for the development
of what some of us affectionately call the “rootless corn” or “floppy corn”
syndrome. The problem illustrates a classic example of the importance of the
timing of stress and plant development.
The permanent (nodal) roots of a corn plant develop initially from near the crown area of the plant (Nielsen, 2010). They develop sequentially in sets or “whorls” from individual nodes of the lower stalk. The growing point or meristem of a root lies near the root tip and must remain alive in order for the root to develop normally.
Contrary to popular opinion down at the coffee shop, roots do not intentionally grow toward moisture. They grow downward in response to gravity (i.e., a gravitropic response) and will continue to proliferate if soil conditions (temperature, moisture, porosity) are conducive for root growth.
If nodal roots begin their elongation in bone-dry surface soil and reach adequate soil moisture at deeper depths before the meristmatic root tip desiccates, then the root will survive and proliferate. If the root tip (and its accompanying meristem) desiccates prior to reaching soil moisture, the entire young nodal root will likely die. This is particularly true if the axillary meristems along the length of the root (that eventually produce the branch roots) have not yet differentiated or become active.
Desiccated & dead nodal roots.
The appearance of such a desiccated root is what one would imagine; shriveled and discolored. This symptom is unlike that of any other lethal root stress, including salt injury from fertilizer. These symptoms are NOT like any associated with herbicide injury or insect feeding. Because several sets of roots may not have formed belowground, the crown may "appear" to be at or above the surface. That appearance is an optical illusion except in a few cases (Nielsen, 2004).
Entire sets or “whorls” of nodal roots sometimes die in this manner and the plant essentially survives on what’s left in the kernel reserves and what the seminal roots offer in terms of moisture and nutrient uptake until the next set of nodal roots develop and become established. If subsequent sets of nodal roots die in the same manner, the plant continues its dependence on the kernel and seminal root support.
In fact, it is amazing to me how the aboveground appearance of a plant affected with the “rootless” syndrome can remain fairly normal up until the windy day when the mesocotyl simply can no longer support the plant and it flops over to the ground. “Floppy” corn plants are NOT technically root-lodged; they are simply broken over at the mesocotyl below the crown area of the plant. Obviously, the health of the mesocotyl and the seminal roots determine whether an affected plant can “hang on” until a decent soaker occurs to replenish soil moisture levels.
"Slightly shallow" seeding depth.
What Can Be Done to Alleviate the Problem? Unfortunately, very little can be done to prevent the situation from becoming worse. Row cultivation may encourage new nodal root development if moist soil is thrown around the base of the plants. However, if the soil is dry enough to be causing the problem in the first place, there's probably very little moist soil shallow enough to be brought up by row cultivation. The ultimate solution to the problem is a good soaking rain or at least enough of a rain to sustain new nodal root development long enough to allow the roots to reach deeper and hopefully wetter soil conditions before the upper soil dries again.
"Hindsight” Reminders or Foresight Advice.
- “Rootless” corn develops more easily with extremely shallow seeding depths that result in nodal root initiation beginning nearer the soil surface than at the usual 3/4 inch depth. This is one of several reasons that growers should avoid choosing seeding depths shallower than about 1 to 1-1/2 inches.
- Furrow erosion as a result of heavy rains after planting can create "shallow planted" seed as a consequence of removing top soil.
- Shallow soil compaction from shallow tillage of fields that are "just a little on the wet side" can restrict initial nodal root development in the shallow, and often dry, soil above the compacted layer.
- Open seed slots resulting from no-till planting "on the wet side" can contribute to the desiccation and death of initial nodal root development if the initial nodal roots desiccate before they successfully penetrate through the furrow sidewalls.
Click on an image to open a larger version.
Corn at V5 to V6.
Root system of "normal" plant.
Early stage of "floppy" corn.
Early stage of "floppy" corn.
Absence of established nodal roots.
Broken mesocotyl.
Related References
Elmore, Roger and Lori Abendroth. 2007. Rootless Corn Syndrome. Integrated Crop Management Newsletter, Iowa State Univ. [On-line] at http://www.ipm.iastate.edu/ipm/icm/2007/5-21/rootless.html. [URL accessed April 2010].
Lauer, Joe. 2001. Rootless or "Floppy" Corn. Wisconsin Crop Manager Newsletter, Univ. of Wisconsin. [On-line] at http://corn.agronomy.wisc.edu/WCM/W090.aspx. [URL accessed April 2010].
Nielsen, R.L. (Bob). 2004. Over-Extended Mesocotyls and Floppy Corn Syndrome. Corny News Network, Purdue Extension. [On-line] at http://www.kingcorn.org/news/articles.04/FloppyCorn-0624.html. [URL accessed April 2010].
Nielsen, R.L. (Bob). 2007. Variable Emergence Due to Variable Seedbed Moisture. Corny News Network, Purdue Extension. [On-line] at http://www.kingcorn.org/news/articles.07/VariableEmergence-0520.html. [URL accessed April 2010].
Nielsen, R.L. (Bob). 2010. Root Development in Young Corn. Corny News Network, Purdue Extension. [On-line] at http://www.kingcorn.org/news/timeless/Roots.html. [URL accessed April 2010].
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