Proper root development during the first few weeks following corn emergence is critical to the success of the crop. Mesocotyl rot can occur in corn seedlings at this stage of growth with the right combination of environmental conditions. Alison Robertson addressed this issue in Corn seedling health and stand establishment
Corn has two root systems that are easily visible early in the year. The initial root system, the seminal roots, is comprised of the radicle and lateral seminal roots. The seminal roots help anchor the young seedling and provide it with nutrients and water (see the Image Gallery for a picture of a normal seedling root).
The shoot is comprised of the mesocotyl and coleoptile. The second root system, the nodal roots, develops at the base of the coleoptile. The location of the nodal roots is typically the same unless the seed was planted extremely shallow. They should form approximately 1 to 1.5 inches below the soil surface. The mesocotyl connects the kernel and the coleoptile. The mesocotyl length will vary depending on seeding depth (see figure 1).
Figure 1: Mesocotyl and coleoptile development across different seeding depths. Seeding depth on the left is approximately 3" progressing to 1/2" on the right. Picture taken at the Armstrong Research and Demonstration Farm on May 16, 2006.
Seminal roots cease new growth shortly after the coleoptile emerges from the soil surface. Once the plant is approximately V1, the nodal root system is visible. The corn in the picture is in between V1 and V2, and the initial development of the nodal roots is visible. The nodal root system becomes the dominant system by V6.
A healthy mesocotyl is extremely important since it transports nutrients from the kernel to the developing seedling. The plant primarily depends on the kernel's contents for its nutrients and energy until the nodal roots are developed. Therefore, it is possible that seedlings may be stunted or die if their nodal roots do not develop before the kernel reserves are exhausted. It is helpful to check fields at this point in the season for root development to determine if seedlings are healthy.
Another useful reference related to this topic is Root development in young corn by Bob Nielsen, Extension Corn Specialist, Purdue University.
Portions of this text, written by Lori Abendroth and Roger Elmore, originally appeared in the Integrated Crop Management extension newsletter on page 132 of the IC-496(12) - May 22, 2006 issue.