Scientists at Purdue University have come up with a way of growing corn in caves, but it doesn't involve some bizarre mating of maize and mushroom. Instead, they manipulated artificial light and temperature in such a way that the growth of the corn plants, while stunted, didn't significantly affect the seed yield. The finding could have a significant impact on the future of genetically modified crops by helping prevent genetically modified pollen escaping into the ecosystem.

Growing plants in caves and old mines may seem counter intuitive, but it’s a well-established practice in the field of genetic engineering. Manipulating genes in plants and animals can not only throw light on the mysteries of life, it also allows organisms to produce chemicals that would otherwise be difficult or expensive to obtain, such as sheep that give milk with spider silk mixed in, or bananas that contain vaccines. These are not always genes that you want to get out into the wild, so setting up a farm in a salt mine starts to make sense.

The only problem is that, obviously, caves make very poor substitutes for a few acres of prime farming land. Not the least reason is that many plants grow too high for underground galleries with low ceilings. It is possible to breed plants that are dwarf varieties, but that also runs into the problem of smaller plants with smaller yields.

Researchers Yang Yang, left, and Cary Mitchell (Photo: Purdue University)

In addition, some plants are more suited to genetic engineering than others. According to the Purdue team, corn is a "good candidate crop" for an engineered product because it has a high yield, and the genome is well mapped and is easily modified compared to, for example, mammal cells. Unfortunately, corn grows 8 ft (2.4 m) tall, which brings in that height problem again.

What the Purdue team did was take a page from commercial greenhouses that grow Christmas poinsettias and tricked the plants into stunting their own growth. They managed this by planting the corn in a disused mine chamber that was heavily insulated, so the environment could be carefully controlled in terms of light, temperature, and carbon dioxide levels.

The scientists then provided the corn plants with an artificial “day” of 16 hours of light at a temperature of 80⁰ F (26⁰ C) and 8 hours of darkness at 65⁰ F (18⁰ C). The clever bit is that for the first two hours of “daylight,” they dropped the temperature to 60⁰ F (15⁰ C). This altered the corn’s growth rate, so the stalks were up to 10 percent shorter, but the number and weight of the kernels was roughly the same.

"Grains of corn could be engineered to produce proteins that could be extracted and processed into medicine, pharmaceuticals and nutraceuticals such as essential vitamins," says Cary Mitchell, professor of horticulture. "This is a young industry, but what we've done is show that you can successfully grow these high-value crops in contained environments."

In addition to genetically modified crops, Mitchell says that the technique could have more general application because the natural coolness of mines and the ability to provide plants with high levels of carbon dioxide means that crops could be grown with a much greater degree of environmental control.

"Productivity in a controlled environment is superior to that in the field, and you can raise more than one crop per year," Mitchell says. "Controlled environment agriculture is going to be one of the big movements of the 21st century."

The team’s findings were published in Industrial Crops and Products.

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