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tassel produces about 250,000 pollen grains to complete fertilization on the 800 to 1,000 silks that emerge from each ear.
Pollen shedding begins with the extension of the anthers in the middle of the center spike and continues over the entire tassel. Pollination normally occurs between 9 and 11 a m., but can occur earlier in hot, dry conditions and will be delayed in wet weather.
The elongation of the stem holding the anther occurs rather rapidly and may require only 10 to 15 minutes. Once the anther has emerged fromt he tassel, the tip splits open, and a large number of pollen rains are released.
Corn Pollen One of
Largest Pollen Grains
Com pollen is one of the largest pollen grains dependent upon being disseminated by wind. Most will fall within 30 to 40 feet, but some can be carried by the wind for long distances. Pollen shed from one tassel will continue over a period of five to eight days.
If conditions are too wet one day, there may not be any pollen shedding. Often, there are several pollen grains germinating on the same silk. The one reaching the ovule first completes fertilization.
After the silk is fertilized, food supply to that silk is cut off, and the silk dies. Silks continue to elongate until fertilized and remain receptive to pollen for about one week. After fertilization, about 50 days are required for the kernel to mature.
Three Reasons for
Poor Pollination
Poor * pollination can occur because of hot, dry weather. This failure may be the result of several factors:
1) Dead pollen — Under magnification, the pollen looks around. Flat spots on pollen indicate dead or malformed pollen.
2) Silk emergence being delayed past the optimum or peak pollen shed.
3) The silk being too dry to cause the pollen to germinate.
Poor pollination results in a scattering of kernels over the entire ear. Most often, the failure of kernels on the tip of the ear to develop is the result of stress to the plant (soil to dry, low fertility), rather than poor pollination.
Dr. Diane Relfis horticulture specialist with Virginia Cooperative Extension and is a member of the faculty of Virginia Tech.
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