Tasseling and detasseling
About three weeks ago, I stopped along Old Highway 68/80, east of Hopkinsville, and took this photo of the Little River Valley. In the distance, a field of corn is growing in the rich bottom land along the river. It appears as a yellow patch because all the corn plants were tasseling (blooming). The tassel is the male flower of the corn plant.
Pollen grain germination occurs within minutes after a pollen grain lands on a receptive silk. A pollen tube, containing the male genetic material, develops and grows inside the silk, and fertilizes the ovule within 24 hours. Pollen grains can land and germinate anywhere along the length of an exposed receptive silk. Many pollen grains may germinate on a receptive silk, but typically only one will successfully fertilize the ovule.
Source: "Silk Emergence" at the Corny News Network
When hybrid seed corn is grown, two varieties of corn are planted in a field, but only one variety is allowed to tassel. The tassels on the other variety are removed manually (often by teenagers who need a summer job) and/or by machine, or sometimes a corn variety with sterile tassels is planted.
The ears that grow on the detasseled plants will have hybrid seeds (kernels) -- a cross between two varieties. All of the corn kernels from ears on the tasseled plants are simply "chips off the old block", now a little more inbred.
After the corn tassels, the whole energy of the plant is devoted to growing the ear/s of corn and filling the kernels with all the nutrient and genetic material it will need for germination. The plant will not develop any more leaves or get any taller.