"Zipper" Pattern of Poor Kernel Set in Corn
RL (Bob) Nielsen, Extension Agronomist, Purdue University
An uncommon pattern of poor kernel set is one that is often described as the "zipper" pattern wherein one or more entire rows of kernels along one side of a cob are absent due to some combination of pollination failure and kernel abortion. A subsequent symptom that often develops on such "zipper ears" is a noticeable curvature of the cob, sometimes to the extent that folks describe it as a "banana ear". These curved ears are a consequence of the absence of kernels on one side of the cob coupled with the continued development of kernels on the other side that "force" the cob to bend or curve.
While most recognize that the absence of kernels down one side of the ear is the result of severe photosynthetic stress, it is less obvious why the pollination failure or kernel abortion occurred along that side of the ear rather than being localized at the tip of the ear. Silk development typically begins with the basal ovules at the butt of the ear and progresses up the ear which means that the first silks to emerge and be fertilized are primarily from the basal half of the ear. This acropetal progression of silk elongation is thought to occur uniformly from base to tip such that silk emergence occurs uniformly around the circumference of the ear at any particular position on the ear. Consequently, severe stress during or after pollination usually results in poor kernel set near the tip end of the cob. If this is true, then what is the cause of the "zipper" pattern of poor kernel set?
The answer is too lengthy for this brief Picture of the Week. Check out the complete article at http://www.kingcorn.org/news/timeless/Zipper.html
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Fig 1. Stress due to severe devoliation shortly after polllination.
Fig 2. "Zipper" pattern of poor kernel set.
Fig 3. Stress due to excessive heat and inadequate soil moisture.
Fig 4. Stress due to nitrogen deficiency.