Corn silks are annoying, but they’re also amazing. The longest styles on the planet don’t make it easy for corn pollen to do its job. Gain new respect for your corn on the cob.
Fresh corn (Zea mays, Poeaceae) is a summertime treat. Shucking corn silks, though, can be a pain. Corn silks, however, are amazing, and maybe knowing why will ameliorate their annoyingness. Formally corn silks are the style, the part of the female flower that intercepts pollen. Female flowers of many species have a stigma, a sticky pad, atop their styles to intercept pollen, but corn silks are lined with sticky trichomes (like hairs) that essentially do the same thing. Corn silks are incredibly long styles. Can you think of another plant with a flower appendage that could rival it? I can’t. The tassels at the top of the corn plant bear male flowers that shed pollen into the wind. Pollen shed and silk receptivity must be in sync in a corn field in order for pollination to occur (and for us to get yummy corn ears), a period called “nick” by farmers and only about 4-8 days in length. Once a pollen grain lands on a silk, water and sugar on the surface of the silk “germinates” the pollen grain, and the pollen tube begins to grow. The pollen tube is a single cell within the pollen grain that elongates along only one end, into the corn silk. The pollen tube grows up to 12 inches through the silk until it reaches the ovule, fueled by water and nutrients from the silk. Two male nuclei travel inside the pollen tube’s cytoplasm (cellular fluid) to the ovule. One male nucleus fuses with the egg cell in the ovule to produce the embryo, and the other fuses with two additional female nuclei in the ovule to form the endosperm tissue. The endosperm tissue grows into the nutritious part of the seed, both for the embryo and for us. The whole process from pollen interception to fertilization takes no more than 24 hours, a marvel of cellular growth.
More than one pollen grain may land on a single silk, and their pollen tubes will race to the ovule. To recap: every ovule inside of an ovary is attached to a corn silk style. In order for the ovary to develop into a corn kernel (the seed), a pollen grain must successfully send a pollen tube down the corn silk, and fertilization must occur. Why must silks be so long? Much of the length is simply attributable to the size and structure of the corn ear. The silks from the ovules at the base of the ear are longer than those at the top. Part of the length, too, must be because corn plants are so lush and bear their ears relatively low on the plant. Many other grasses (family Poaceae) put their female flowers on a tall stalk above the leaves, so the pollen in the wind hits the flowers before the leaves. Not so with corn. The silks may have to compensate for their position with surface area. For other hypotheses, though, I’m all ears, so to speak. So, next time you tediously pick silks from a perfect ear of corn, feel grateful for the heroic pollen tubes that made it possible.
Special thanks to Lynda Delph, who confirmed for me that corn silks are extraordinary styles.