Cold Injury of Corn

Last week I discussed some of the most common corn seedling diseases that occur in Ontario and how the conditions this spring have been favourable for their development. This week I came across an article by Peter Thomison (Corn Specialist) and Pat Lipps (Plant Pathologist) from The Ohio State University that provides a good review of the impact that persistent cold and wet conditions have on germinated corn seedlings and seeds. They wrote:

"Damage from cold temperature stress adversely affected the germination of seeds and the growth of young seedlings and probably predisposed the plants to invasion by soil fungi capable of causing seed rot and seedling blight. In addition to slowing the germination process, cold temperatures, snow and freezing rain from April 20-25 may have caused irreparable harm to the delicate structures of emerging corn seedling.

When dry corn seed absorbs cold water as a result of a cold rain or melting snow, "imbibitional chilling injury" may result. Cold water can cause similar injury to seedling structures as they emerge during germination. Such injury in corn seed ruptures cell membranes and results in aborted radicles, proliferation of seminal roots, and delayed seedling growth. When temperatures remain at or below 50 degree F after planting (as they did this year for two weeks) damage to germinating seed is particularly severe. Many of the corn seed planted shortly before the cold temperature stress of April 20-25 have produced seedlings exhibiting symptoms which are characteristic of imbibitional chilling injury (e.g. stunted or aborted radicles).When this physiological damage is combined with surface soil crusting, saturated soil conditions, compacted soils, deep seed placement, and seedling blights, you have a recipe for emergence problems."

Bob Nielsen, Corn Specialist with Purdue University adds that "lethal cold temperatures (28F or less) can penetrate the upper inch or two of soil, especially dry surface soils, and kill plant tissue directly, including coleoptiles and growing points.

Figure 1- Coleoptile injury due to lethal cold temperatures. (Pioneer Hi-Bred Int.)

Non-lethal injury by cold temperatures in comparison may cause deformed elongation of the mesocotyl or physical damage to the coleoptile, resulting in a "cork-screw" symptoms and subsequent leafing out underground.

Figure 2 - Lethal cold temperature injury in developing corn seedlings.
(Pioneer Hi-Bred Int.)

The following images are from Robert Nielsen, Corn Specialist with Purdue University. Figure 3 is of a corn seedling that is leafing out underground. Figure 4 is of a corn seedling that is displaying "cork-screwing" symptoms.

Figure 3 - Corn seedling leafing out underground
(Photo courtesy B. Nielsen)

Figure 4 - Cork-screw symptoms of young corn seedlings
(Photo courtesy B. Nielsen)

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