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Here a fungus sets a trap for a nematode,
killing it and setting nutrients free for plant roots. |
Fungal adaptations Fungi have developed all sorts of clever strategies to make it through life—our nematode-strangling fungus proves it. The fungus that developed this very artful and useful adaptation is Arthrobotrys dactyloides. The ring that trapped the nematode is actually just a hyphal branch, twisted back on itself. These branches each consist of only three cells, which, when touched, produce a signal to let water in; the cells then swell to three times their size and the unsuspecting victim is killed in a tenth of a second . Pretty amazing— a sophisticated trapping mechanism developed from an inverted branch using only three cells. Once again, nanotechnology can only hope to duplicate such a complicated process.
Not only does the fungus figure out a way to kill nematodes, which are all blind, but it attracts them to its trap in the first instance. In this case, the fungus releases a chemical that attracts the worm. Within a matter of only a few minutes after trapping, the tip of a fungal hypha enters the nematode’s body, secretes its powerful enzymes, and starts absorbing nutrients. As this is exactly what the nematode has been doing— eating— the worm is usually a real treasure trove of nutrients for the fungus. These nutrients, of course, are then locked up inside the fungus until the fungus is eaten by one of its predators or it trades them for exudates. Then the nutrients are mineralized and again are available to plants.
Jeff; Lowenfels, Wayne Lewis, (2010-09-10). Teaming with Microbes: The Organic Gardener's Guide to the Soil Food Web, Revised Edition (Kindle Locations 921-925). Timber Press. Kindle Edition.
The more I read this book, the more I think the authors are writing about Intelligent Design - or
gasp - Creation. Whatever their philosophy, the facts remain startling and revealing.
Gardeners are used to thinking about the big players in nature - earthworms and plants. The underlying story is microscopic - fungus, nematodes, bacteria, springtails, and protozoa. Fungus and bacteria are rotting agents, the largest amount of work done by fungus. Nematodes, bacteria, and protozoa team up with fungus to break open chemical bonds to deliver useful nutrition to the plant's roots.
Look at a sycamore leaf. That leaf is so tough that it can last the winter without changing shape or rotting. The leaf's chemical bonds resist breaking down, while a maple leaf will get soft, papery, and rot rather quickly. The sycamore leaves have more value when broken down than in simply covering the soil as an almost permanent mulch. Earthworms and springtails shred leaves, making it easier for the fungi to begin its work.
The Lord of Creation arranged for the Soil Team to deliver simple compounds to the roots in exchange for the chemical compounds they need to grow. One creature alone could not do this, but billions of microscopic denizens do, and the larger ones share in the work.
The fungus Pleurotus ostreatus, the common oyster mushroom you can buy at the supermarket, uses another clever technique to trap food. It emits toxic drops from the tips of its hyphae; an unsuspecting nematode (our perennial fungal fall guy), out and about, looking for food, touches a drop with its mouth and within minutes is immobilized. A few hours later, and the fungus is inside the nematode, already digesting it. This is not a bad way to ensure a meal : attract your food and either trap it or stun it and then consume it. Other mechanisms have evolved as well. Some fungi use adhesives to stick to nematodes. Other soil fungi trap protozoa and even springtails, much larger microarthropods that are big enough to see with the naked eye. Once attached, the fungi digest their prey and again lock up or immobilize plant nutrients.
What drives soil fungi in the direction of particular nutrients is still an open question. It is known that some send out filaments as if they were scouts looking for nutrients. If you have ever seen a well-trained bird dog look for a downed bird, you get the idea . The dog circles until its nose finds the bird.
Some fungi clearly possess tactile- or contact-sensing capabilities that allow them to orient in a certain direction so they can invade their prey or other food source. Others demonstrate the ability to track specific chemicals they know to be in the vicinity of specific prey. For the gardener it is sufficient to know that fungi can find nutrients. When a source is found, fungal strands head over to the area and literally settle in, digesting the material, often combining one nutrient source material with another and transporting nutrients back to the base of the fungus. All the while, other strands “scout” for more food to attack . Nutrients are held inside cell walls, preventing them from leaching away.
Wayne Lewis, Jeff; Lowenfels,(2010-09-10). Teaming with Microbes: The Organic Gardener's Guide to the Soil Food Web, Revised Edition (Kindle Locations 931-939). Timber Press. Kindle Edition.
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Little Ichabod and I had to learn this to pass the CCNA test.
The Soil Team's work is far more complicated. |
Organic gardening means favoring the fungi, bacteria, nematodes, springtails, and protozoa to lock up food and break it down in the root zone, especially next to the growing root tips. Cisco graduates will recognize that this preceded the engineering of the Internet. A computer breaks down pictures, words, and sound into tiny data packets. They are sent out as 1s and 0s but re-assembled into the original in the receiving computer.
Thus the Soil Team sends packets of nutrition from a rotting cabbage to the plant roots on the organic Internet, and the plant assembles those chemical packets into stems, leaves, flowers, fruit, and seed of another plant. A dead mouse can become a tomato, but without the disease elements of death and decay, cleansed by the antibiotic properties of fungi and bacteria.
Finding and bringing back the phosphorus that is so critical to plants seems to be a major function of many mycorrhizal fungi; the acids produced by mycorrhizal fungi can unlock, retrieve, and transport chemically locked-up phosphorus [the P in NPK - for root and shoot growth] back to the host plant. Mycorrhizal fungi also free up copper, calcium, magnesium, zinc, and iron for plant use. As always, any nutrient compounds not delivered to the plant roots are locked up in the fungi and are released when the fungi die and are decayed.
Wayne Lewis, Jeff Lowenfels, (2010-09-10). Teaming with Microbes: The Organic Gardener's Guide to the Soil Food Web, Revised Edition (Kindle Locations 981-985). Timber Press. Kindle Edition.
Clearly, fungus can do what the inorganic salts cannot. The bag of fertilizer from the hardware store passes through the soil layer into the water table. Organic amendments build up the Soil Team and hold the nutrients in the root zone. That is how I deliver dozens of roses to friends without using bags of expensive fertilizer to juice the soil.
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This era will be remembered as the time
when the historic liturgy was traded for cotton candy cacophony. |
