FUNGI

Fungi are plantlike in that many are stationary. However they are heterotrophic, they do not have chlorophyll. Becauce they cannot move to capture food, fungi are either parasites or saprophytes. They absorb small molecules of food from a host or the environtment. Most true fungi have filamentous stalks called hyphae. In some fungi, each hypha is a mass of cytolasm containing many nuclei and no cell walls. In others the hyphae are composed of definite cells. A mass of hyphae is called a mycelium. The cell walls of most fungi are composed of chitin, a carbohydrate material. Some forms are unicelluler and lack hyphae.

Fungi reproduce by forming spores and by other means. Thickened walls of the hyphae and spores are adaptatoins which permit fungi to live on land.

Sporangium Fungi The common bread mold, rhizopus is a member of the phylum zygomycota or sporangium fungi. In this phylum, spores are produced in sporangia. Sporangia are structures located at the tips of certain hyphae. The hyphae are called sporangiospores. They stick up above the food source giving the fungus a fuzzy appearance.

Other hyphae called stolons spread along the surface of the food suply or substrate. In addition to sexual reproduction by means of spores, bread mold can also reproduce sexually. Still other hyphae,rhizoid anchor the fungus to the food source. Thus rhizoids resemble roots in function. Rhizoid enter the substrate and secrete enzymes that break the food molecules into simpler molecules. The simple molecules diffuse into the rhizoids and throughout the mold.

Most relatives of the bread mold are saprophytes that decompose dead organisms for their food. As a result, valuable materials are returned to the soil and atmosphere. However, some species such as the downy mildew are parasites that cause disease by feeding on many plants, including potatoes ang cereal grains. They produce rhizoids that penetrate the tisues of the host plant and rob it of nutrient materials

Club Fungi Mushroms are a clas of fungi that have shaped, spore producing structures called basidia. The phylum is basidiomycota or club fungi. Also in this phylum are shelf fungi, rusts, smuts and puffballs. Mushroms are important because many of them are edible. The edible part of mushroom is only the reproductive part of the organism. Undergroundis a brancing network of hyphae that obtain nourishment in much the same way as does bread mold.

The button portion of the mushroom develops as a small out-growth of the mycelium in the soil which pushes through the soil and develops into a stalklike section, the stipe and an umbrelalike cap. Beneath the cap are spokelike gills on which basidia are located. Each basidium produces four spores which can be dispersed by the wind.

Sac Fungi Yeast, cup fungi and powdery mildews are all members of phylum Ascomycota, the sac fungi. In each of these organism, the zygote develops into a saclike structure, the ascus Yeast are unusual fungi in that they are unicellular. Recall that they are important in both the brewing and baking industries. They are also very important in research because they are simple eukaryotes.