The sex life of corn

Corn, the key species in modern industrial agriculture, is completely incapable of reproducing itself in nature. The cobs that concentrate the seeds so nicely for us are not conducive to reproduction because, if planted, the corn grows so densely it dies. As such, the continued existence of Zea mays depends upon people continuing to divide the cobs and plant a portion of the seeds.

Corn is apparently a descendant of an earless grass called Teosinte. It is hard to overstate the consequences of a heavily mutated strain of Teosinte finding a species capable of closing a reproductive loop that would otherwise be open, leading to swift extinction.

The actual mechanics of corn reproduction are similarly odd. Male gametes are produced at the top of the plant, inside the flower-like tassel. At a certain time of year, these release the pollen that fertilizes the female gametes located in the cobs. It reaches them through single strands of silk (called styles) that run through the husk. When a grain of pollen comes into contact with one of these threads it divides into two identical cells. One of them tunnels through the strand into the kernel, a six to eight inch distance crossed in several hours. The other fuses with an egg to form an embryo, while the digger grows into the endosperm.

Another curious aspect of corn reproduction is that, because of seed hybridization (not genetic modification), every stalk of corn in a field is a clone of every other stalk. This is because the seeds came from inbred lines: each made to self-pollinate for several generations, eventually yielding batches of genetically identical seeds that farmers buy every year. They do this because the yield from the identical seeds is higher than that from the mixed generation that would follow it by a degree sufficient to justify the cost of buying seeds.

Such hybrid corn pushed yields from twenty bushels an acre – the amount managed by both Native Americans and farmers in the 1920s – to about two hundred bushels an acre. Given the degree to which we are all constructed more from corn than from any other source of materials (most of the meat, milk, and cheese we eat is ultimately made from corn, as are tons of processed foods), these remarkable processes of reproduction and agriculture deserve further study. For my part, I am reading Michael Pollan’s The Omnivore’s Dilemma. I am only 10% into it, but it has been quite fascinating so far.