John Cooke

Alive & Kicking

Pollination & The Cob

By John Cooke

During boyhood, I was proud of my sweet corn patch.

I always planted Golden Bantam seeds from the American Seed Company. I sold their seeds as advertised in "Boys Life" magazine in hopes of earning one of their exotic prizes: B-B guns and the like.

The corn I grew tasted wonderful, but I always wondered about those missing kernels - potholes on those otherwise beautiful ears of corn. As I chomped along a yellow row-kerplunk, my teeth would stumble into a hole left by a missing kernel, breaking my stride. It was less than total success. Like a sommelier at a wine tasting finding KoolAid in his sampling sequence, my concentration was shattered.

What's more, the cob tip was not fully developed!

Years passed; it was in a botany class when the old question surfaced.

I knew what pollination was, the transfer of pollen from one reproductive flower part to another by wind, insects, or touch.

The female flower in corn is the ear, and the tassel is the male flower.

(Some plants get the job done in one flower. Still others have male plants and separate female plants.)

So what happens to the pollen grain?

First, it is plant-specific. Pine pollen will not work on tomatoes. In some apple species, the tree's pollen is not mature when that plant's flowers are ready to be pollinated. This requires that other apple tree species in the area have mature pollen to enable fruit production. This results in "cross-pollination." Bees are often essential to this process.

In corn, the pollen cell nuclei from the tassel grow a microscopic tube called the pollen tube, which grows through the length of a single corn silk strand (corn silk is that sticky string-like stuff that is hard to peel off of a fresh ear of corn when you husk it). This long silk strand leads the growing tube and its contents to the immature kernel, where fertilization occurs to form the complete seed. Each kernel must be fertilized independently.

Armed with this lecture and my weak powers of extrapolation and synthesis, I have concluded that potholes in corn cobs are caused by a breakdown in the pollination, pollen tube growth or fertilization sequence. Further, I conclude that corn silk strands that lead to the kernels on the tip of the ear must lie toward the center of the silk mass and are likely shielded from pollination.

After learning these poignant pothole points, I have become "amaized" that this complex pollen-initiated sequence ending in fertilization provides so successfully for the next corn crop with such a magnifi cent excess for human and animal consumption-and maybe some ethanol production on the side.

I rest my case. Humans should be grateful.

Guest columnist John Cooke taught high school biology for 30 years and is pleased to share his insights with our readers.