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.

Author: Milan

In the spring of 2005, I graduated from the University of British Columbia with a degree in International Relations and a general focus in the area of environmental politics. In the fall of 2005, I began reading for an M.Phil in IR at Wadham College, Oxford. Outside school, I am very interested in photography, writing, and the outdoors. I am writing this blog to keep in touch with friends and family around the world, provide a more personal view of graduate student life in Oxford, and pass on some lessons I've learned here.

22 thoughts on “The sex life of corn”

  1. Hybrid corn

    Nearly all the field corn now grown in the United States and most other developed nations is hybrid corn. Modern corn hybrids substantially outyield conventional cultivars and respond better to fertilization.

    Heterosis in maize was first demonstrated in the early 20th century by George H. Shull and Edward M. East. They showed that crosses of inbred lines made from a Southern dent and a Northern flint, respectively, showed substantial heterosis and outyielded conventional cultivars of that era. However, at that time such hybrids could not be economically made on a large scale for use by farmers. Donald F. Jones at the Connecticut Agricultural Experiment Station, New Haven invented the first practical method of producing a high-yielding hybrid maize in 1914-1917. Jones’ method produced a double-cross hybrid, which requires two crossing steps working from four distinct original inbred lines. Later work by corn breeders produced inbred lines with sufficient vigor for practical production of a commercial hybrid in a single step, the single-cross hybrids. Single-cross hybrids are made from just two original parent inbreds. They are generally more vigorous and also more uniform than the earlier double-cross hybrids.

  2. “One of them tunnels through the strand into the kernel, a six to eight inch distance crossed in several hours.”

    Weird. It’s odd to imagine plant cells doing this.

  3. The Moral Instinct

    “Dozens of things that past generations treated as practical matters are now ethical battlegrounds, including disposable diapers, I.Q. tests, poultry farms, Barbie dolls and research on breast cancer. Food alone has become a minefield, with critics sermonizing about the size of sodas, the chemistry of fat, the freedom of chickens, the price of coffee beans, the species of fish and now the distance the food has traveled from farm to plate.”

  4. Corn prices rose to an all-time high today, and the largest U.S. farm group predicted that prices would remain high over the next year as ethanol refiners continue driving demand.

    Corn futures reached $5.12 a bushel on the Chicago Board of Trade — more than a dollar above last year’s price and topping the previous high set in May 1996.

    The rally for corn continues what has been an upward price trend, as global demand for feed and biofuel has outpaced production. Corn sold for close to $2 per bushel in 2006, then doubled to more than $4 per bushel last year.

    The high prices have strained livestock producers who feed corn to their animals and pressured upstart ethanol plants whose business plans were built on lower corn prices.

    Economists from the American Farm Bureau Federation predicted today that corn prices would continue to be high over the next year. In its annual economic outlook report, the Farm Bureau said corn would average $4.60 a bushel in 2008-2009 but that it could cost significantly more if there are any production problems.

    Farm Bureau senior economist Terry Francl said $7.50 corn is “not out of the question” in the next year, although he conceded it is unlikely to reach that level.

    “We are entering a new dynamic in agriculture that doesn’t come along very often,” Farm Bureau President Bob Stallman told reporters today at the group’s annual meeting in New Orleans. “There is a huge new demand in biofuels, but that is not the only driver.”

    The farm group says the high prices are not just from ethanol, but also due to increasing worldwide demand, high prices for non-agriculture commodities like crude oil, the continuing decline of the dollar and low production of corn last year in some other countries.

    Rising corn prices led U.S. farmers last year to plant more acres of the crop than the United States has seen in more than 60 years. But despite the increase in corn acres, the Agriculture Department said Friday that the U.S. corn stockpile is expected to shrink to a mere five-week supply by late summer.

  5. Doesn’t this mean that, as a society, we are highly vulnerable to “Corn Terrorism” ie. maliciously devising & introducing pests or disease that would destroy the corn crop? For some reason, that’s got me thinking about the Pirate Song…

  6. While I am no expert on corn biology, it seems unlikely that such terrorism would be successful. Pests would just be dealt with using more spraying.

    Also, even a large disruption in one part of the world could be partially made good through imports. The price of corn would probably rise, but it probably wouldn’t fundamentally disrupt the food system.

    That said, I could be wrong.

  7. Does anyone know what the citation information is for this article? Sorry if it is somewhere on the website but I have not been able to find it. I am hoping to use some of this info for part of a research paper due tomorrow and would really appreciate some help with the citation.

  8. A blog post isn’t a very credible source for a scholarly paper. Nonetheless, most citation styles include methods for citing webpages.

    For instance, I think the proper MLA citation for this page would be:

    a sibilant intake of breath. “The sex life of corn.” 13 January 2008. <; (Accessed 22 February 2009)

    Other styles (Chicago, etc) would involve slightly different formatting.

    That being said, you would be far better off citing the Wikipedia entries linked above.

  9. ok thank you very much. I understand this isn’t the best source but I have many more sources that are more credible. Also I am a senior in high school so I doubt I will be docked heavily for one or two sources such as this. I am really only using it for the quote explaining the way corn is pollinated. The paper is over discussing the harmful affects that large agribusiness companies (like monsanto) have on farmers, the environment, and nutrition in food. If you have any suggestions for good primary sources on that topic please let me know.
    By the way, I am also currently reading The Omnivore’s Dilemma and it is really interesting. :)

  10. Ok really appreciate the help. I was sick for two weeks straight and got stuck finishing this 9-11 page paper in one weekend. (just in case you are wondering why I seem disorganized)

  11. For your paper, it is worth at least considering whether there are any benefits that large agribusiness companies provide to farmers, the environment, or nutrition.

    For instance, one can argue that they help lower the cost of food, improving the nutrition of the poor. Farmers also choose to buy proprietary hybrid seeds, even when non-proprietary seeds are available, because they increase yields.

    Overall, I do think that the global agricultural model is deeply flawed. That being said, reforming it is more a matter of changing farming practices (such as excessive use of pesticides and fertilizers, soil depletion, antibiotics for livestock, etc) than about changing the corporate structure of farming entities.

  12. I totally agree. However, government policy (heavily influenced by large agribusiness companies) appears to favor those farmers who practice industrial agriculture. As far as I understand many farmers did not understand what industrial agriculture could mean in the future. Switching back to sustainable methods is quite difficult if you have been practicing industrial techniques for some time. Also I am not sure about this but I believe organic farmers recieve no subsidies. I work for an organic farm/grassfed beef company at a farmers market in Houston. While we have some steady customers, it seems that in a city as large as Houston there would be much more demand for sustainable dieting than I have observed. It is extremely difficult to convince someone that it is worth paying twice as much for our food than the food in the grocery store. I have only started teaching myself about the problems with the food industry in the last few months so I am sure you are more knowledgeable. This is just what I have read and observed. I will attempt to discuss the other side of cheap food but I feel 9-11 pages is difficult to fit everything in. I am having trouble organizing it since I feel I could either write a 3-4 page short summary or 20+ pages if I try to write any more than a summary.

  13. The topic is an enormous one. It involves everything from global equity to climate change to marine dead zones to mad cow disease to poverty alleviation in the third world to intellectual property to genetics to moral philosophy, and more.

    That being said, a condemnation of industrial agriculture is likely to be stronger if it also examines some of the points that those defending it would employ.

  14. Ok thanks a lot for the input. I will certainly try to include some of the defending arguments. If you want to clean up the page you can delete some of my posts but please leave your responses up until tomorrow so that I may refer to them.

  15. Being informative is one of the major purposes of this site. As such, this conversation is well within the ordinary remit.

    Good luck with your paper, and with the organic grass-fed farm.

  16. definitely interested but I think I will postpone responding to the thread until I am done with my paper. I certainly understand the post though. I originally went vegetarian in august and then learned more and have made variations in my diet. I eat grassfed beef somewhat regularly but much less than the amount of beef I ate before learning more about this whole “omnivore’s dilemma.”

  17. I am reading Michael Pollan’s book, In Defense of Food. It’s a good book to read after, The Omnivore’s Dilemma.

  18. I’m not so sure about the conclusion that domesticated maize could not propagate itself w/o human farmers to separate the seeds. Like teosinte, which I have seen in abundance in the Sierra de Manantlan of Mexico, the seeds would more than likely be separated and dispersed to some degree by animals (incl humans). Would the percentage of seed successfully propagating itself equal that of a farm field seeded with individual seed? No way, but I do not think species extinction would be the result. Interestingly, teosinte only exists in somewhat human disturbed environments, secondary forest and forest openings, so even in it’s non-domesticated form, maize has a long, long, long history of interaction with humans.

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