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Soil Insects - Pests or Fodder for Plants?

Lacking any creative thoughts of my own this month, here are excerpts from an article in Science News (Vol. 159, April 7, 2001) that I found fascinating:

"For some plants, a nitrogen-rich diet from dead matter in soil just isn't enough. Researchers from the University of Guelph in Ontario are discovering that these plants also rob nitrogen from the flesh of tiny soil dwelling insects. But instead of doing the job themselves, the plants rely on fungal partners in crime.

Fungi of the species Laccaria bicolor attach to the roots of the eastern white pine, where they lure tiny insects commonly known as springtails, says study leader John N. Klironomos, a soil ecologist. The fungus then kills the insects, perhaps with a toxin, and sucks up nitrogen from the insects' bodies to nourish itself. The host plant takes any leftover nitrogen. In return, the plant supplies the fungi with energy rich carbohydrates.

About 95 percent of plants get nutrients such as nitrogen and phosphorus with help from various types of fungi, says Klironomos...Fungi typically attach to plant roots and then send out fibrous branches, which can infiltrate dead matter. When that happens, the fungi break down the organic materials using enzymes and absorb nutrients...To see how much of the plant's nitrogen came from the insects, the researchers radioactively labeled nitrogen atoms in the insects' bodies and followed their trails in eastern white pine seedlings. They found that after 2 months, 25 percent of the plant's nitrogen had come from the insects. "That's very significant," says Gopi K. Pidila, a molecular biologist at Michigan Technological University in Houghton. "It's almost like (the plant is) actively seeking nitrogen from the insects and getting it through the fungus"

There are several other studies by other researchers that show the same phenomenon with nematodes, so it seems a safe assumption that not only do the mycorrhizal fungi protect their host plant roots by forming a physical barrier, but also turn potential soil pathogens into plant food. I like that idea. It explains why plants without mycorrhizae on their roots are far more vulnerable to underground predators.

The only quibble I have with the article above is the suggestion that plants are the dominant organism in the equation. In my opinion, the microscopic fungi are far more in control of the underground actions and are "programmed" to keep their carbo-generating host plants well-nourished. As the fungi are the older life form, and are genetically closer to humans than are plants, it seems logical to me that plants therefore have the more passive role in the insect ambushes. These mycorrhizal fungi are tiny, but just might be smarter than plants.

Good growing, my friends,

Don Chapman
President, BioOrganics, Inc.

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