A tassel of male flowers can produce 25 million grains of pollen. Corn BeltDent SouthernDent Northern Flint How kernels develop Teosinte,corn’s wildancestor Silk Silk Pollen tube Egg Ovule Pollen tube Trichome (a tiny hair that catches pollen) Pollen Ear Ovule Silk Each silk leads to a tiny ovule that will swell into a kernel, but only if fertilized. Corn relies on wind for pollination. The tassel’s pollen is heavy, usually falling within only about 10 feet of the plant. If a grain of pollen sticks to a silk, a pollen tube quickly sprouts from the grain and grows down the length of the silk, carrying male genetic material. In less than a day, the pollen tube reaches the ovule to fertilize the egg. The resulting zygote stimulates the growth of a kernel, which accumulates sugars that will later turn into hard starch if the cob is allowed to mature. Corn (native Americans called it “maize”) was first cultivated in southern Mexico about 9,000 years ago. When European colonists arrived, they encountered two races of corn in eastern North America: Northern Flint and Southern Dent, which they cross-bred to develop Corn Belt Dent, the ancestor of most corn hybrids today. Corn is one of many crops that in recent decades have been genetically modified to be resistant to herbicides, drought and insects, the last of which have begun to develop resistance to the toxins engineered into every part of the plant. Corn conception Pollen’s role Fertilization An evolution driven by humans Squanto taught Plymouth colonists to plant corn in the spring — “when oak leaves are as big as a mouse’s ear.” Corn’s own ears are mature 65 to 90 days later. Ears nearest the top are always largest. They can be harvested when they feel plump at the tip, about 20 days after silks emerge. Silks are elongated parts of the female flower, or ear. Light green when they emerge, silks stop growing once they’re pollinated, drying out and turning rusty brown as the kernels mature. Depending on the hybrid, corn might have from 13 to 17 leaves. Corn always has an even number of rows of kernels. Silking stage (ovules) Blister stage (fertilized kernels) Milk stage(best for eating) Dough stage Dent stage Maturity

SOURCE: Proceedings of the National Academy of Sciences, University of Nebraska, Purdue University, PLOS One.