Basidiomycota. Botany 201 Laboratory Spring 2007

Transcription

1 Botany 201 Laboratory Spring 2007 Basidiomycota As was the case of the Ascomycota, this phylum represents a very variable group of fungi. This only characteristic that is common to all species in this group of fungi is that they produce basidiospores, externally, on the sterigmata of basidia during sexual reproduction. The cell wall is, again, primarily chitin. Basidia and basidiospores may be produced directly on mycelium or on structures called basidiocarps. Today, we will only consider those species that produce basidiocarps. Many species produce clamp connections, swellings that are associated with septa of the dikaryotic mycelium. These play an important role in maintaining the binucleate condition of the dikaryotic stage of the life cycle. Although primarily mycelial, some taxa produce a yeast stage during the monokaryotic stage of their life cycle. When asexual reproduction occurs, which is not common in this division, conidia are produced. Three classes are recognized: Basidiomycetes, Uredinomycetes and Ustomycetes. We will only cover the Basidiomycetes during this lab. I. Class: Basidiomycetes Species in this class produce basidia that are unicellular to septate. Basidiospores may be forcibly ejected and dispersed by wind or in those species in which spores are not forcibly ejected, various interesting mechanisms of spore dispersal have evolved. All members of this class produce basidia and basidiospores in basidiocarps. A. Order: Tremellales The order Tremellales is one of several orders commonly referred to as jelly fungi because of the gelatinous consistency of their basidiocarp. The basidia are said to be cruciate-septate because, when viewed from above, under a compound microscope, the septa of the basidium is divided into four chambers of approximately the same size, by septa, which forms a cross. The basidia and basidiospores are borne on a hymenium. Representative Tremellales to be examined: Tremella boraborensis 1. Tremella boraborensis: Draw the demonstration of the characteristic basidium of this order and a few basidiospores. 2. Examine some commercially cultivated species of jelly fungi and note the variations in their morphology. B. Order: Dacrymycetales 15

2 This is another order of jelly fungi. This order differs in the morphology of the basidium, which is referred to as a tuning fork basidium because of its resemblance to a tuning fork. Basidia and basidiospores are borne on a hymenium. 1. Dacryopinax spathularia: Draw and describe the demonstration of the basidium in this species. C. Order: Agaricales This is the order in which mushrooms are classified and is the most familiar to the non-mycologically informed. Mushroom basidiocarps are generally monomitic. This characteristic gives the mushroom basidiocarp its firm, fleshy consistency. The basidiocarp is usually composed of a stipe (=stalk), a hymenium that is in the form of a lamella (=gills of the mushroom), and a pileus (=cap). The basidia and basidiospores are borned on the surface of the lamella. Basidia are typically club-shaped and non-septate. However, variations do occur. Some mushrooms are sessile and some produce hymenia that are in pores rather than gills. Representative Hymenomycetes to be examined: Agaricus bisporus 1. Agaricus bisporus: This species is the common supermarket mushroom. There are actually several varieties of this species that are quite different in appearance (see demo, below). This species is structurally, representative of the typical mushroom. Draw the mushroom and label the stipe (=stalk), pileus (=cap) and lamella (=gills). Mushroom produce gilled hymenia. Make a thin section through the gills of this mushroom, and mount in 3% KOH and stain with phloxine. Identify and draw a basidium with its sterigmata and a few basidiospores. How many sterigmata do you see on the basidium? Compare this type of basidium with Tremella boraborensis. Draw the basidiocarp and label the parts described above. 2. Examine the demonstrations on other cultivated species of mushrooms and note the variations in their morphology. D. Order: Aphyllophorales 16

3 This order has fungi whose basidiocarps are generally leathery to woody rather than fleshy due to the presence of dimitic or trimitic hyphae. These fungi are commonly referred to as "conks" or "polypores". The basidiocarps are variable in shape as is the hymenium, which may be smooth, have lamella, pores, teeths, etc. These species are often found as decomposers on woody substrates. Representative Basidiomycetes to be examined: Ganoderma australis, Sarcodon atroviridis and Schizophyllum commune 1. Ganoderma australis: Basidia and basidiospores of this species are borne in a hymenium that consists of pores. Because the pores are very small, you will need a hand lens or a dissecting microscope to see the pores of this species. Also, note the very woody consistency of this basidiocarp. Do you think that this is entirely fungal? Draw the basidiocarp and indicate where the pores are produced. 2. Sarcodon atroviridis: Basidia and basidiospores are borne on the surface of a hymenium that consists of spines on the basidiocarp. Draw the basidiocarp and indicate where the spines are produced. 3. Schizophyllum commune: Basidia and basidiospores are borne on the surface of a hymenium that consists of gills. How does this differ from the Agaricales? E. Various cultivated mushrooms Many species of mushrooms are cultivated for food. Look at some of the demonstrations of cultivated species: Agaricus bisporus has several variety that have been cultivated, two here are the A. bisporus proper and the Portabello, Pleurotus ostreatus (Oyster mushroom) and Lentinellus edodes (Shitake). Other species cultivated include Tremella fuciformis (Silver ear), Auricularia polytricha (Ear fungus or Pepeiao) and Ganoderma lucidum (Reishi). Gasteromycetes (=Puffballs) The taxon, Gasteromycetes, no longer has any official status. It represents an array of fleshy fungi that are of different phylogenetic lines. However, they do share an important characteristic. Because puffballs do not forcibly eject their basidiospores, they 17

4 have evolved various mechanisms by which they disperse their spores. They also differ from other Basidiomycetes in that their basidia and basidiospores are not produced in a hymenium. Another term, the gleba, is used to refer to the part of the basidiocarp where the basidia and basidiospores are borne. Some of the orders, below, will be examined to illustrate some of the interesting mechanisms that have evolved for spore dispersal. E. Order: Lycoperdales This order produces basidiocarps that are globose, to pyriform, with an ostiole where the basidiospores are released. The basidiocarp is a flexible "sac" or peridium that encloses the basidiospores or gleba. At maturity, the spores are dry and powdery. When an object, such as a raindrop or small mammal depresses the peridium, the force pushes the basidiospores out the ostiole, in what appears to be a cloud of smoke, and disperses them into the air where they are carried by the wind. Representative Lycoperdales to be examined: Lycoperdon sp., 1. Lycoperdon sp: Examine the basidiocarp displayed. Draw and identify the peridium and ostiole of the basidiocarp. Gently, push your pencil against the peridium and observe the powdery basidiospores as they are puffed out the ostiole. F. Order: Phallales This order is commonly called the stinkhorns because of the offensive odor that they emit. They come in various size and shapes with glebas that are usually very slimy in appearance and dull grayish-brown in color. The part of the basidiocarp underneath the gleba is usually a bright color that is masking a bright shade of yellow, orange, red or green, underneath. The combination of the gleba color, offensive odor and bright color attracts flies that disperse the basidiospores. Representative Phallales to be examined: Aseroe rubra 1. Aseroe rubra: When fresh, this species of stinkhorn has a slimy, grayish-brown gleba and is bright red in the surrounding area. Although the preserved specimen is very poor, attempt to draw the basidiocarp of this species and identify the gleba. How are the basidiospores dispersed in this and other stinkhorns? Where is the peridium in this fungus? G. Order: Nidulariales 18

5 This group is commonly referred to as the bird's nest fungi because their appearance superficially resembles a bird's nest with eggs. The "eggs" are the peridioles, which contain the basidia and basidiospores. In this mechanism, it is the peridioles that are dispersed. Although the mechanism of dispersal is an interesting one, it is not one that carries the fungus any great distances. However, it does spread it, continuously, over a large area, at small, distance intervals with each dispersed peridiole. The peridioles are splashed out of the peridium (=nest) by raindrops up to a distance of approximately 24". As the peridoles are ejected out of the peridium, the sudden ejection causes a rope-like structure, the funiculus that is neatly coiled in the peridiole to unwind. A sticky area, the hapteron, at the end of the funiculus can attach itself to a nearby substrate. If this occurs, the sudden stop causes the funiculus to wrap around and attach itself to the substrate. Representative Nidulariales to be examined: Cyathus sp. 1. Cyathus sp.: The basidiocarp of the bird s nest fungi is the most complex among the Gasteromycetes. Draw and identify the peridium and peridiole. Dissect a peridiole under the dissecting microscope and identify the funiculus and hapteron. A demonstration showing how dispersal is accomplished will be carried out during this lab. 19