LABORATORY
EXERCISE #9
KINGDOM FUNGI
- KINGDOM PLANTAE
THE FUNGI
AND THE NON-VASCULAR PLANTS
Part I - The
Fungi
Although the fungi are usually studied by botanists (plant biologists), they
belong to a separate kingdom. While
there are some similarities between plants and fungi, there are also major
differences, the most conspicuous being a
lack of chlorophyll in the fungi.
This means that the fungi are all heterotrophs,
either parasitic or saprophytic. Saprophytes obtain energy from dead
organic matter, while parasites live
on or in, and at the expense of, a living host. Another major difference between plants and fungi is in the
composition of the cell wall, which in most fungi is composed of chitin - as in the exoskeleton of
arthropods - rather than the cellulose of plants.
The body of the fungus is termed a mycelium, and is composed of many
thread-like hyphae. The mycelium is usually diffused within the
substrate on which the fungus lives and is seldom seen by humans. The most conspicuous part of the fungus is
usually the fruiting body,
constructed of a dense network of hyphae, which assumes a rather consistent
shape in many taxa. The structures
termed "mushrooms" or "toad stools" are examples.
The fungi, though somewhat humble organisms, impact
our lives in many ways. They ruin our
clothes, rot our homes, contaminate our food supplies and infect our
bodies. They are also serious plant pathogens, causing more diseases in
plants than do bacteria. On the
positive side, we rely on fungi to make our bread light, add a unique taste and
smell to ripe cheeses and contribute a bit of a "kick" to some of our
favorite beverages. We also rely on the
antibiotic properties of some fungi as we manufacture important medicines. The most important divisions (phyla) of
Kingdom Fungi include:
ACTIVITIES
a. Obtain a slide of the black bread mold, Rhizopus nigricans. On this
slide you can find both the sexual
and asexual stages of the life
cycle. Page 24 in Perry and Morton
shows a series of photographs illustrating the asexual phase. Find and identify the following parts: columella, sporangiophore, sporangium, spores, and hyphae. Now, using illustrations 25a-c on page 25,
locate the sexual stages, as exemplified by the zygospore. Note the rough,
dark wall of these resistant spores.
They are formed only following sexual reproduction.
2. The
largest division of Kingdom Fungi is called the sac fungi. This
group includes such tasty delights as truffles and morels (Photo Atlas, Figure
27b), as well as some of the most dangerous pathogens. The name "sac fungus" comes from
the tiny sacs in which the sexual spores are produced (See textbook figure
19.16a, page 321). Diseases caused by
sac fungi have devastated two of North America’s most important forest trees. Dutch elm disease has decimated the American
elm, a prized shade tree, and chestnut
blight has virtually eliminated the American chestnut from the forest.
ACTIVITIES
b. Pizza
has small, cup-shaped fruiting bodies of the type shown in Figure 27f in
the Photo Atlas. The slide of Pizza shows a section of one of these fruiting bodies. Examine it first on low power and identify
the hymenium (See Fig. 27d in Perry
and Morton), then increase the magnification and focus on the top of the
hymenium. Locate the tiny, sac-like asci (singular is ascus) with their
enclosed ascospores.
c.
See the specimen labeled "Morel". This fungus is found in our area and is much
prized for its flavor. Considered to be
"king" of the American mushrooms, it is locally known as "dry
land fish".
3. The fungi
probably familiar to most students belong to the club fungi . This
includes most of the common mushrooms,
including the ones commercially available in your grocer's produce section,
along with the puffballs and bracket fungi. Also included are the rusts and smuts;
serious agents of disease in the cereal grains. Figure 19.14 in your textbook (p. 319) shows the development of a
typical mushroom, as well as the formation of the tiny "clubs" or basidia on which the sexual spores
develop.
ACTIVITIES
d. Obtain a specimen of the meadow mushroom, Agaricus campestris, similar to Figure 28a. This is the common edible mushroom. Carefully slice the fungus in half, using a
single-edged razor blade. Identify the cap, stalk, gills and annulus. These specimens are probably not mature enough to release spores.
e. Select a slide labeled Coprinus. This is a cross-section through the cap of a
tiny mushroom. Use Figures 28b & c
to find and identify the cap, stalk, gills, basidia and basidiospores.
f. The bracket or shelf fungus (Figure 28e) is a saprophyte, which grows
attached to dead trees and/or logs.
Some may live many years and their age can be determined by counting the
rings on their upper surface. While
these are club fungi, they lack the gills of the familiar mushrooms. Instead, their lower surface is marked with
zillions of tiny pores from which
mega-zillions of spores fall.
4. The lichens are included here for
want of a better place. They do not
exactly fit into our scheme of classification because they are composite organisms. A lichen is composed of a fungus - usually a sac fungus - and an alga.
The arrangement seems to work well for both species, with the fungus
giving the alga a moist, protected place to live, with adequate light, and the
alga providing food for both through photosynthesis. While there are many interesting lichens, we can lump them into
three categories:
A. The crustose lichens form a thin crust over
the substrate, usually a rock or tree. These lichens look as though they have
been spray-painted on!
B. The foliose lichens are leaf-like. One could easily use a fingernail to pull
them from the surface on which they are growing.
C. The fruticose lichens are described as
shrub-like. They are sometimes used as
miniature trees or shrubs in model railroad landscapes.
ACTIVITIES
g. Examine the lichen specimens provided and be able to place them in the
categories listed above. Use the
photographs on page 40 of Perry and Morton for assistance.
Part II - The
Non-Vascular Plants
The Kingdom
Plantae is generally considered to include all the multicellular, autotrophic
organisms. They typically have a cell wall of cellulose and store
energy in the form of starch. They also have an interesting life cycle,
which consists of alternating sexual and asexual stages. Meiosis in the plants leads to the formation
of spores rather than gametes.
The Algae
While most of the plants with which we are familiar
are terrestrial organisms, one group
is overwhelmingly marine or aquatic. These are the algae.
Because these plants live in the water, they have not evolved the
support tissue required by land plants, nor do they need special tissues to
transmit water from one part of the plant to another. Since the tissues that
perform these tasks in terrestrial plants are termed vascular tissues, the algae are included with the non-vascular
taxa.
The term "algae" has no technical meaning
today, as we know that the three groups are not really closely related and
probably represent separate branches of the evolutionary tree. We simply retain the term to mean the multicellular, non-vascular aquatic plants. There are three divisions (phyla) of algae.
A. The red
algae are nearly all-marine organisms.
While the majority of these plants are a wine color, owing to a red pigment, some are blue-green and others
are nearly black! Red algae have the
ability to use the wave lengths of light that penetrate most deeply into the
water, consequently, they can inhabit far greater depths than most other
plants. Several types of red algae are
used as human food and the common laboratory medium, agar, is extracted from one species.
B. The brown algae also have accessory pigments
that mask the green of their chlorophyll, giving them a brown to olive color. This
group includes some of the largest of plants, the giant kelps, which grow in dense "beds" and which may exceed
100 meters in length. The more common rockweed, seen along eastern beaches,
is also a brown alga. Humans and
domestic animals consume some of the kelps, and a chemical stabilizer, algin, derived from brown algae is used
to make frozen desserts "creamy".
C. While some
of the multicellular green algae
are marine, most are confined to freshwater.
This line is probably ancestral
to the land plants. The green algae
is an extremely diverse group, including
filamentous and colonial plants
which barely fit the concept of multicellularity, along with much larger and
more complex taxa.
ACTIVITIES
h. Examine the
herbarium mounts (dried specimens, mounted flat on a large sheet of heavy
paper) of red, brown and multicellular
green algae. Be able to identify
them as algae and know the group to which they belong. Studying the illustrations on pages 32-34 of
the Photo Atlas should help.
The Bryophytes
Division Bryophyta contains the plant equivalents to
the amphibians. These plants are
terrestrial organisms which have not been able to divorce themselves from the
water. They lack vascular tissue,
which means no true roots, stems or leaves, and must therefore retain a small,
low-growing plant body. The bryophytes
also have motile sperm, a holdover
from their algal ancestors, and must have at least a thin film of water for
fertilization to be affected. For the
most part, then, the bryophytes are limited to moist, shady habitats.
Turn to Figure 19.4 on page 310 in your
textbook. This illustrates the life
cycle of the moss, a typical bryophyte.
Note that it is divided into two parts, the gametophyte generation, which is haploid (has only one of each
chromosome pair in its cells) and the sporophyte
generation, which is diploid (has two of each type of chromosome). In the moss - and indeed all bryophytes -
the gametophyte is the most conspicuous and dominant of the two
generations. The green bed of moss that
you see in the woods is a bed of moss gametophytes! This is the sexual stage of the life cycle, producing gametes in
special organs termed the antheridia
(male) and archegonia (female).
The fertilized egg or zygote represents the beginning of the sporophyte generation. The rather inconspicuous moss sporophyte is
the asexual stage and produces, through meiosis,
many haploid spores that are released in great clouds and blown by the wind to
disseminate them about the countryside.
These spores mark the beginning of the gametophyte generation.
There are two major groups of bryophytes, the mosses and the liverworts. We will
examine the mosses as representative bryophytes.
ACTIVITIES
i.
Examine the specimens of dried and fresh mosses. Can you recognize
the gametophyte? How about the sporophyte? Use Figure 45f
and 46a in Perry and Morton for assistance.
j.
Obtain a slide of Mnium (moss) antheridial head. This is a section through a male gametophyte
of the moss. Use Figures 45b and c to
assist you in locating the antheridia
and the sperms.
k. Next examine a slide of Mnium (moss) archegonial head. This shows the female gametophyte. Figures
45d and e may be used to assist you in locating the archegonia, the swollen area termed the venter, and the egg.
l.
Finally, look at the slide of the
Mnium (moss) mature capsule. This shows a section through the capsule of
the moss sporophyte. With the
assistance of Figure 46b, identify the
operculum, spores and columella.