Effects of cold injury to corn uncertain until harvest
Farmers with recently planted and newly emerged corn need to watch their fields for cold injury, even though much of the damage likely won’t be known until harvest, a Purdue Extension corn specialist says.
Corn planting has been off to a slow start for Indiana farmers due to cold temperatures and soggy soils. On May 5 the U.S. Department of Agriculture reported that 20 percent of Indiana’s corn crop had been planted, compared with a 34 percent five-year average. Much of what has been planted went into cold soils, meaning farmers need to watch the crop for injury as it emerges and determine whether replanting is necessary.
“Where soil moisture was acceptable for planting, some growers accepted the risks associated with cold soils and corn germination or initial seedling development and planted corn,” Bob Nielsen said. “Should they be concerned about the health of their newly planted and, in a few cases, newly emerged crops? We’ll know for certain come harvest time, but in the meantime, we can talk about possibilities.”
For newly planted corn, one of the possibilities is what researchers call “imbibitional chilling injury.” This type of injury happens within 24 to 36 hours of planting when the kernel absorbs, or imbibes, water and begins the germination process. When it’s cold, this can cause damage to plant cell tissues.
The symptoms of imbibitional chilling injury include kernels that are swollen but not showing other signs of germination; or slowed growth of the radicle root or coleoptile (sheath tissue that protects leaves during emergence) once the initial germination occurs.
Newly planted corn also can suffer non-imbibitional chilling injury during emergence.
“This type of chilling injury is more closely related to physical damage to the outer cell tissues that literally cause death of the plant part or inhibit further elongation of the affected area,” Nielsen said.
That means injury can include stunting or death of the seminal root system, deformed elongation of the mesocotyl and either delayed or failed emergence.
The mesocotyl is the part of the plant that connects the crown and the seed. During emergence, the mesocotyl extends and pushes the coleoptile toward the surface. Damaged sections of mesocotyl tissue stop growing, while healthy tissue continues to grow longer.
“Thus, chilling injury to only part of the circumference of the mesocotyl results in the corkscrew symptom as the undamaged sections of the mesocotyl continue to elongate.”