Cold temperatures and rainy spring weather can be hard on corn stands, causing uneven emergence and poor uniformity. It occasionally also turns corn seedlings purple. Should this be a major concern?
Not necessarily, according to Ignacio Ciampitti, crop production and cropping systems specialist with Kansas State University.
“At this point, the purple color is simply the result of a small degree of cold temperature stress – nothing severe,” he says. “The plant is growing very slowly due to the cool weather (not related to the purple color, he notes), but good growth and development should resume after the temperatures go back to the normal for this time of year.”
Other potential causes of purple corn seedlings include phosphorus deficiency, restricted root growth and a build-up of sugars due to sunny days and cold nights. With phosphorous deficiency, corn plants will be stunted with thin stalks. Therefore, it becomes important to look how healthy, uniform and vigorous the stand is to properly diagnose what is happening.
So what is causing the purpling if the crop looks otherwise healthy? It’s a matter of genetics, Ciampitti says.
“The color is coming from the expression of genes for anthocyanin pigment formation,” he says. “Multiple genes govern the expression of this color, and certain cold-sensitive genes react to low temperatures of 40 to 50 degrees. Therefore, low nighttime temperatures will promote purpling in corn seedlings.”
This particular condition is expressed up until the V6 stage, Ciampitti adds. If purple color persists beyond V6, it’s time to consider taking a soil sample to test for potential phosphorous deficiency, he says.
Moreover, several researchers have concluded that yield is not likely to be affected by this phenomenon – however, it’s a good practice regardless to scout acres early for potential problems, Ciampitti says.
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