Fascinating Fungi

Forest and Bird, Issue 294, 1 November 1999, Unnumbered Page

Fascinating Fungi

—Kate Mulligan.

: few mushrooms with your bacon?’ ‘Mmm, yes please!’ Some fungi are delicious; truffles are so highly prized that they can sell for several thousand dollars per kilogram. Other fungi are very poisonous. Fungi play a part in the production of many things that are good to eat or drink: fresh bread, blue vein and brie cheeses, wine and beer. Some fungi contaminate foods with toxins; some produce powerful antibiotics which can be used to treat bacterial infections. Fungi are intriguing and brightly coloured treasures to be found in the garden, on bush walks, or jaunts to the park. In the past fungi have been classified in the Plant Kingdom but unlike green plants they cannot make their own food by photosynthesis for none of them possess chlorophyll. To live they must have organic food, such as carbohydrates and protein etc., more in the the style of animal nutrition. So now they are classified in a Kingdom all to themselves: the Fungus Kingdom. Unlike animals, fungi don’t move around to find their food. Instead, they grow on or in their food — be it wood, fruit, leaf mould etc. — secreting enzymes which

digest the food outside their bodies which is then absorbed and used for growth. Most fungi grow as microscopically thin strands called hyphae, which repeatedly branch to form a network called a mycelium. The mycelium penetrates all parts of the food that the fungus is using. Fungi which live off dead organic material are called saprophytes, whereas those that live on living organisms are parasites. Some are able to do both. Armillaria, (a parasite that attacks a number of plants including kiwifruit vines), will continue to live on the host it has killed. So what do fungi do when they’ve used up the food on which they are growing? They have to reach another source and they do this by making spores. Spores are tiny reproductive structures which can remain dormant through long periods of inhospitable conditions, then germinate to produce a new mycelium if they land on a suitable surface. Spores are so small that they are carried far and wide by air currents and are present in every lungful of air we breathe. To make spores, the mycelium forms a special fruiting body which pushes up into the air. These fruiting bodies are the things we call mushrooms and toadstools. Each one releases millions of spores so there is a good chance that some of them will reach a new food source and start a new mycelium. So when you happen upon a toadstool

on a bush walk, remember that it is just the tip of the iceberg and hidden beneath is the fungus network of feeding mycelium. The largest single living organism in the world has been found to be an Armillaria mycelium sprawling across 600 hectares in the state of Washington, USA. It has been calculated that the total mass of this individual would be 400 tonnes; bigger than a blue whale! In all ecosystems, fungi play a vital role as decomposers. They help to recycle dead material into mineral salts in the soil, ready for renewed uptake by plants. Logs of solid wood transformed to crumbling dust testify to this power. Mycorrhizal fungi are even more intimately involved with plant nutrition. These form a mutually beneficial relationship with plant roots. The fungus partner

helps the plant to take up nutrients from the soil and, in return, the fungus may share some of the carbohydrate made by the plant. This is why we often find toadstools popping up around a tree, as does the fly agaric, Amanita muscaria, around pine trees. The mycelium that produces these white-spotted red toadstools has formed a mycorrhizal association with the roots of the pine tree.

There are many ingenious ways in which fruiting bodies launch their spores for dispersal. The most common method is that of the agarics which have gills under an umbrella-shaped cap. Spores produced in the gills fall down and are blown away. Boletes, like the sticky bun fungus Boletus granulatus, have the familiarshaped cap but, instead of gills, the spores are produced in cylindrical tubes beneath it. Curiously, the pouch fungi, like the blue tobacco-pouch fungus, Weraroa viriscens, never open to release their spores. Instead

they may be dispersed by fungi-eating invertebrates or by birds fossicking for insects. Puff balls, like the velvet earthstar, Geastrum velutinum, form a dry mass of spores which puff out from a small central hole at the slightest touch. The bird’s nest fungus, Crucibulum laevae, produces miniature cups containing ‘eggs, which are little packets of spores. When rain drops ‘plop’ into the cup, the ‘eggs’ are splashed out. A foul stench attracts flies to the basket fungus, Ileodictyon cibarius, thought at one time to be ‘ghost’s droppings’ tutae kehua and you can understand why. Basket fungus and its close relation the red ‘flower’ fungus Aseroe rubra, produce a sticky, stinking, spore mass on which flies crawl. The flies feed on the spores and carry them away sticking to their bodies.

Most macabre are the fungi which infect underground cicada nymphs and porina caterpillars. Having fed on an insect’s tissues, and replacing them with fungal mycelium, the fungus sends a fruiting stalk up above ground from which to shed its spores. The insect corpse, packed with fungal mycelium, becomes a ‘vegetable cicada’ or ‘vegetable caterpillar’. The sheer variety of fungal fruiting bodies is a cause for wonder. Textures range from woody to jelly-like. Sizes range from caps only a couple of millimetres in diameter to bracket fungi that are big and strong enough to sit on. Colours range from the palest creams and mushroom hues to the most vivid such as the bright blue of Entoloma hochstetteri. Fungi are mysterious in their sudden appearance, and ephemeral in duration. To me, they are mystical, curious life forms. It is always disappointing to see toadstools kicked to smithereens at the side of a track. Let’s pause to admire them instead. Remember also their essential role in silently driving the cycles of nature.

KATE MULLIGAN

is an organiser of the Kiwi Conservation Club, and current secretary of the Tauranga Forest and Bird committee.