Fungi& Lichen Lab

Equipment:.Compound and dissecting microscopes, slides and coverslips, forceps, prepared slides, living specimens.

Purpose: to illustrate the anatomy and life cycles of various types of fungi

to show the relationships that fungi have developed with other plants.

Background:

Commonly known as yeasts, molds, mildews, rusts, blights, mushrooms and puffballs, the fungi are common organisms in the ecosystem. The typical body of a fungus is in the shape of long filaments called hyphae. The hyphae branch to form a dendritic pattern of interconnecting filaments collectively known as mycelium. No tissues are found in the mycelium and all cells are generalized to preform most of the functions of the organism. The hyphae are surrounded by cell walls made of chitin. In some fungi, the hyphae are divided by cross walls called septae, but these can be perforated allowing cytoplasm to flow from one compartment to the next. Most fungi are coenocytic...many nuclei are found in a single large cytoplasm. During the life cycle each nucleus is usually haploid.

Fungi are heterotrophic but because of their chitinous cell walls, they can’t engulf food so the hyphae secrete digestive enzymes that can break down organic matter which is then absorbed into the hyphae.

Some parasitic fungi produce haustoria, which penetrates the hosts cells and absorb food materials produced by the host.

Asexual reproduction usually occurs and hyphae can differentiate into sporangia that produce asexual spores.

Sexual reproduction occurs in a few ways, 1. fusion of gametes, and 2. fusion of a motile gamete with a specialized reproductive structure called a gametangium 3. fusion of gametangia.

Lab Instructions: In this exercise you will examine the anatomy, life cycle and biology of several fungi.

1. Sac Fungi(fig.16.3): Mildew is a term used to describe discoloration and odors caused by fungi growing in moist areas. Plant pathologists use this term to describe diseases of plants in which fungi grows on the leaf surfaces. Examine the life cycle of powdery mildew (fig.16.3) and examine the mildews and discolored leaves on the lab table with both types of microscopes.

(palm leaves, sago leaves, rose leaves and the others that are discolored)

What stages in the life cycle can be observed?

Find the modified hyphae, the haustoria, that projects into the cells of the leaf and absorb nutrients in a parasitic relationship. Projecting up from the leaf are other modified hyphae called conidiophores that form asexual spores called conidia.

Draw and label using these terms next to the life cycle

Examine and draw examples of Microshaera alni and Aspergillus. Also check out the rust on the wheat..

2. Molds: Examine the rotting fruits. Remove a small piece and place it on a drop of water on a slide, tease it apart, add the coverslip and gently press on it with a pencil eraser to spread the tissue. Examine the specimen for hyphae, conidiophores, and conidia dispersed among the fruit cells.

Do the hyphae grow between the cells or penetrate them?

Are the hyphae septate?

Sketch what you see in the space provided near the life cycles.

Examine the slide of Penicillium conida, draw it.

3. Cup Fungi (fig. 16.4): The fruiting bodies of some ascomycete fungi grow to a large size and are known as ascocarps. Obtain a slide of a section of Peziza and examine its structure.

Compare it to the drawing. Can you see individual hyphae on the slide?

Are the septate or coenocytic?

4. Basidiomycota (fig. 16.6): This is a varied group of saprophytic and parasitic fungi characterized by basidia, club shaped structures that each produce four spores (basidiospores). Puffballs, mushrooms, toadstools, and bracket fungi are the familiar fruiting bodies (basidiocarps) of this group. Beneath the fruiting bodies are extensive dispersed mycelial mats which feed on decaying vegetation. The hyphae are always septate.

Examine the structure of the edible mushroom. Note the cap(pileus) with the gills on its undersurface and the supporting stalk (stipe). This fruiting body, a basidiocarp, is an aggregate of hyphae as is the ascocaarp in the cup fungi. These fungi are heterothallic. Hyphae of the + or - type grow from separate spores and will fuse to form a dikaryotic hyphae. Vegetative growth of such hyphae results in a mushroom.

Split your mushroom longitudinally through the cap and stalk. Look t the cut surface with the dissecting scope.

Can you see hyphae?

Examine the gills for basidiospores hanging from the surface of the basidium.

Examine a prepared slide of a mushroom’s gills and use the compound microscope to locate a basidium.

Examine the slide of the mushroom cross-section...draw it.

Examine the special handout that goes with the mushroom slide.

5. Zygomycota (fig. 16.2): These fungi live in the soil on dead plants and animals. The zygomycetes do not produce flagellated spores nor do they produce a distinct egg or sperm. In sexual reproduction, two mating types of zygomycete hyphae fuse to produce a zygospore, a thick walled sexual spore that develops from the zygote. Asexual spores are also produced from sporangia on the ends of modified erect hyphae. Rhizopus, the black bread mold, illustrates the life cycle of the zygomycete group.

Examine the slides of Rhizopus,, both the sporangia and those conjugating , draw and label what you see. Compare it to the life cycle.

6. Two others: Examine the slide of yeasts (Saccharomycetes) and the water mold slide, Saprolegnia.

Draw each.

7. Lichens (fig. 16.7): Lichens are unique organisms in that they are made up of algae and fungi in a symbiotic relationship and they can now colonize environments that neither could inhabit alone. The fungus absorbs minerals and moisture from the environment and the algae, nestled in the hyphae where they benefit from the absorptive processes, in turn produce carbohydrates and other organic molecules from photosynthesis.

Three types of lichens occur...1. Crustose, grow as a crust on surfaces, 2. Foliose are more or less leafy in appearance and 3. Fruiticose are shrublike with branching and intertwined fibrous parts.

Examine the examples of lichens in the lab...

Look at a slide of a foliose lichen with the compound microscope...can you see the algae concentrated around the hyphae?

Examine the different lichens supplied...especially the red one. Draw it!

8. Mycorrhiza (fig. 16.8): Examine the slide of this important fungi. Compare it to the picture.