Friday, July 24, 2009 7/24/09 - Mushrooms

In today's excerpt - our ignorance regarding mushrooms:"We don't know the most basic things about mushrooms.

"Part of the problem is simply that fungi are very difficult to observe. What we call a mushroom is only the tip of the iceberg of a much bigger and essentially invisible organism that lives most of its life underground. The mushroom is the 'fruiting body' of a subterranean network of microscopic hyphae, improbably long rootlike cells that thread themselves through the soil like neurons. Bunched like cables, the hyphae form webs of (still microscopic) mycelium. Mycologists can't dig up a mushroom like a plant to study its structure because its mycelium is too tiny and delicate to tease from the soil without disintegrating. ... To see the whole organism of which [the mushroom] is merely a component may simply be impossible. Fungi also lack the comprehensible syntax of plants, the orderly and visible chronology of seed and vegetative growth, flower, fruit, and seed again. The fungi surely have a syntax of their own, but we don't know all its rules, especially the ones that govern the creation of a mushroom, which can take three years or thirty, depending. On what? We don't really know. ...

"Fungi, lacking chlorophyll, differ from plants in that they can't manufacture food energy from the sun. Like animals, they feed on organic matter made by plants, or by plant eaters. Most of the fungi we eat obtain their energy by one of two means: saprophytically, by decomposing dead vegetable matter, and mycorrhizally [like chanterelles and morels], by associating with the roots of living plants. Among the saprophytes, many of which can be cultivated by inoculating a suitable mass of dead organic matter (logs, manure, grain) with their spores, are the common white button mushrooms, shiitakes, cremini, Portobellos, and oyster mushrooms. Most of the choicest wild mushrooms are impossible to cultivate, or nearly so, since they need living and often very old trees in order to grow, and can take several decades to fruit. The mycelium can grow more or less indefinitely, in some cases for centuries, without necessarily fruiting. A single fungus recently found in Michigan covers an area of forty acres underground and is thought to be a few centuries old. So inoculating old oaks or pines is no guarantee of harvesting future mushrooms, at least not on a human time scale. Presumably, these fungi live and die on an arboreal time scale.

"Mycorrhizal fungi have coevolved with trees, with whom they've worked out a mutually beneficial relationship in which they trade the products of their very different metabolisms. If the special genius of plants is photosynthesis, the ability of chlorophyll to transform sunlight and water and soil minerals into carbohydrates, the special genius of fungi is the ability to break down organic molecules and minerals into simple molecules and atoms through the action of their powerful enzymes. The hyphae surround or penetrate the plant's roots, providing them with a steady diet of elements in exchange for a drop of simple sugars that the plant synthesizes in its leaves. The network of hyphae vastly extends the effective reach and surface area of a plant's root system, and while trees can survive without their fungal associates, they seldom thrive. It is thought that the fungi may also protect their plant hosts from bacterial and fungal diseases.

"The talent of fungi for decomposing and recycling organic matter is what makes them indispensable, not only to trees but to all life on earth."

Michael Pollan, The Omnivore's Dilemma, Penguin, Copyright 2006 by Michael Pollan, pp. 374-37


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