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Learning with Prof Bup www.bupoyesiku.net Updated 1st January 2020
PLS201: BIOLOGY OF SEEDLESS PLANTS
(Tuber Mushroom)
KINGDOM: FUNGI
OLABISI ONABANJO UNIVERSITY | Department of Plant Science
OLABISI ONABANJO UNIVERSITY PLS201: CRYPTOGAMS
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Contents
Contents ........................................................................................................................................................... 1
Introduction ................................................................................................................................................. 2
Objectives ................................................................................................................................................... 2
Main content ............................................................................................................................................... 2
Background of fungi .............................................................................................................................. 2
Members of fungi ................................................................................................................................... 3
Characteristics of fungi ......................................................................................................................... 3
Forms/Habits of fungi .......................................................................................................................... 10
Habitats of fungi ................................................................................................................................... 10
Ecology of fungi ................................................................................................................................... 11
Economic uses of fungi ...................................................................................................................... 11
Conclusion ................................................................................................................................................ 12
Summary .................................................................................................................................................. 12
References/Further readings ................................................................................................................. 12
Tutorial-marked questions ..................................................................................................................... 13
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Introduction
In our previous lectures, (cryptogams and algae), we discussed the general cryptogams
and the most straightforward group of spore plants, the algae. It is interesting to know that
animals, plants and fungi are specialised multicellular groups derived from kingdom
Protista (algae). In today’s lecture, we shall treat the kingdom of fungi. Fungi is a group of
organisms that share specific characteristics with both plant and animal. Although their
inability to photosynthesise by the lack of chloroplast and cellulose cell walls, their cell
walls are made up of chitin, a component in insect exoskeleton. However, fungi are
capable of producing spores, like the photosynthetic cryptogam plants. Before going into
treating the fungi, we need to know the three basic modes of nutrition in eukaryotic
unicellular and multicellular organisms. These mode of nutrition are ingestion,
photosynthesis and absorption. Now we shall go on to treat the various groups of fungi
and their significant characteristics, ecological and economic uses.
Objectives
At the end of this lecture, we will be able to:
1. raise awareness and extend the knowledge of the fungi
2. have the needed skills to identify members of the fungi around
3. know the importance and the role of fungi in any ecosystem
Main content
Background of fungi
Mycology is the study of the fungi kingdom. The fungi subdivided into two, micro and
macrofungi. The fungi indeed contain some of the most strange and fascinating species.
There are about 100,000 known species. Majority of the fungi around are heterotrophic
(unable to carry out the process of photosynthesis), and they rely on organic nutrients
(cellulose and proteins) from their host or substrate. It is the conventional concept that
fungi secrete a powerful digestive enzyme, outside their body, which breaks down living
or dead organisms into sugars and amino acids. Subsequently, they absorb the nutrient
through their body walls. It will be interesting to know that the individuals of filament
(hyphae) knotted together to form a mycelium. Interestingly, the mycelia (knotted hyphae)
of some fungi can cover an area more than 12 hectares (30 x 2.471) acres of forest floor
underneath the soil surface. No doubt fungi could be one of the world's most abundant
living organisms.
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Members of fungi
Early classification of fungi include five divisions
1. Acrasiomycota (cellular slime moulds)
2. Myxomycota (slime moulds)
3. Oomycota (water moulds)
4. Chytridiomycota (Chytrids)
5. Eumycota-(true fungi)
6. Deuteromycota (imperfect fungi)
The first four divisions, to be discussed in this lecture, are grouped as heterotrophic
protists (slime mould, water mould and cellular slime mould), while the phototrophic
protists are algae (see our previous lecture on the kingdom Protista). This group of
heterotrophic protists generally produces motile cells (including swarm cells and
zoospores) during certain stages of their life cycles. The fifth division of fungi this lecture
is the true fungi, including the family Zygomycetes, Ascomycetes, and Basidiomycetes.
The last division is an exceptional division, with unknown sexual stages. This observation
is remarkably strange because certain species in this division have in the past classified
more than twice by independent taxonomists as member of the family ascomycetes and a
family of Deuteromycetes.
Characteristics of fungi
We are going to discuss here both the general characteristics of fungi and the specific
characters of each division. As we have already known from the start of this lecture, fungi
are acellular or multicellular with well-defined nuclei and rarely are they unicellular
organisms; they have many nuclei occupying the non-partitioned (non-septate) mycelium.
In certain groups, this mycelium becomes partitioned (septate) in reproductive stages of
the life cycle.
As we know from the beginning of this lecture that fungi are unique organisms in
the sense that they are difficult to classify as either plant or animal, instead considered
under a separate kingdom. The comparative characteristics of plant and animal with the
fungi are enumerated here (Table 1).
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Table 1. Comparative characteristics of plant and animals shared with fungi
Attribute Plant Animal
Pigmentation Chlorophylls Melanins/flavins
Cell walls Cellulose Chitin
Nutrition Photo-autotrophic Heterotrophic
Growth form Leafy/thallus Hyphae/Yeast
Stored food Starch Glycogen
At this point, we shall discuss each of the divisions under the fungi in great details.
Acrasiomycota (cellular slime moulds)
The Acrasiomycota division includes the heterotrophic species that exist as separate
amoeba-like structure. Cellula slime mould swarms together to form pseudo-plasmodium
that later differentiates into a fruiting body. Other characteristics of this division include
1. They form sexual reproductive structure (macrocytes)
2. Zygotes (fused pair of mould) attract and ingest single amoeba-like slime moulds
3. Their principal mode of nutrition is by ingestion
4. About 70 species are known
Myxomycota (slime moulds).
The Myxomycota division includes terrestrial plasmodial slime moulds (Fig1). The
common characteristics of plasmodial slime mould include
1. Heterotrophic, multinucleate, creeping, amoeboid plasmodium
2. Adult plasmodial produce multinucleate sporangia that give rise to many spores
3. Sexual reproduction is rare and occasionally observed
4. A dominant mode of nutrition is by ingestion
5. There are approximately 450 species
Oomycota (water moulds).
The Oomycota division includes aquatic and terrestrial species with motile cells at certain
stages of their life cycle. Common characteristics of this division include
1. A pair of flagella (tinsel and whiplash)
2. Cell walls composed of cellulose
3. They store their food as glycogen (animal glucose)
4. Close to 500 species identified
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Figure1. Mobile plasmodial slime mould made of a mass of hyphae forming the body
(mycelium).
Chytridiomycota (Chytrids)
The division Chytridiomycota includes aquatic heterotrophic species with motile cells at
certain stages of their life cycle. Other characteristics include
1. Cell walls made up of chitin
2. Motile cells equipped with single posterior whiplash flagellum
3. They stored their food as glycogen
4. There about 800 species
At this point, we must know that the correct moulds (Eumycota), which is for discussion
next, is subdivided into five classes for your better understanding of this lecture. The
classes include Zygomycetes, Ascomycetes, Basidiomycetes, Hymenomycetes and
Gasteromycetes
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Zygomycetes
The Zygomycetes class includes terrestrial fungi with visible septate hyphae only
during the formation of reproductive bodies. Other characteristics include
1. Cell walls made up of chitin
2. Few forms endomycorrhizal with individual vascular plants
3. There are about 600 species
Ascomycetes
The Ascomycetes class includes terrestrial and aquatic fungi with perforated hyphae
septate. It is interesting to know here that the hyphae portion without perforated
septate mark off for the production of the reproductive propagules (spores or gametes).
Many species in this class have their, hyphae combined to form a cup-like structure
called ascocarps. Other characteristics include
1. Cell walls made up of chitin
2. Sexual ascus cells undergo meiosis to form ascospores
3. Asexual reproduction is by budding as found in Yeasts (unicellular)
4. There about 30,000 species out of which sexual stages do not occur or known in
25,000 species (imperfect fungi)
Note that Deuteromycota (imperfect fungi) will be discussed in details in another
lecture because this division lacks an actual sexual cycle.
Basidiomycetes
The Basidiomycetes class includes only terrestrial fungi. Like in many ascocarps, the
hyphae septate are perforated and the non-perforated septate cut off the reproductive
structure (spores). The sexual reproductive structure is the basidia, which undergoes
meiosis to produce basidiospores. Other characteristics include
1. A pair of nuclei (dikaryotic) within each septate compartment (a unique character
not found in other fungi)
2. They form ectomycorrhizae with higher plants
3. There are about 25,000 species
It is essential also to note here that the division Basidiomycota in addition to
Basidiomycete, include other classes such as Hymenomycetes, Gasteromycetes, and
Teliomycetes, which we shall discuss next.
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Hymenomycetes
1. Formation of basidia in a hymenium (fertile layer consisting of asci or basidia)
2. Basidia (club-shaped sexual reproductive cells) are either septate or aseptate
3. Explosive discharge of the basidiospores (ballistospores)
4. Examples include mushroom, coral fungi, shelf or bracket fungi and tuber fungus
Figure 2. Basidiomycetes. A= Bracket fungus. B=Coral mushroom. C=Bird’s nest
B
A
C
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Gasteromycetes
1. No distinct hymenium (fertile layer)
2. Saprobes growing in soil, dung or dead wood
3. Occasionally form a mycorrhizal association with vascular plants
4. Produce basidiospores
5. Basidiospores discharged passively
6. Examples, puffballs, earthstars, stinkhorns and bird’s nest fungi
Figure 3. Gasteromycetes. A=Puffballs. B=Stinkhorn.
Teliomycetes
1. They do not form basidiocarp
2. They form powdery septate spores
3. They are plant pathogens
4. They produce terminal teliospore (thick-walled resting spores)
5. Teliospores (basidia or sporidia) forcibly discharged
6. Examples, rust and smuts
A B
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Figure 4. Corn smut fungus on an ear of corn
At this point, we need to know the poisonous mushrooms. Few rules of thumb will
guide us as we discuss it next
Characteristics of poisonous mushrooms (Fig 5).
1. white basidiospores 2. a cuplike volva at the base of the stalk 3. a ring or annulus on the stalk further or close to the basidiocarp 4. remnants of the universal veil on the umbrella-like cap (basidiocarp)
Note here that mostly all these traits discussed here are short-lived, depending on the
age and condition of a fungus. These characters are not always reliable to depend upon
to determine the poisonous fungi. Other methods include silver coin and a taxonomic key.
If a coin dropped in boiled mushroom water, it turned black. The mushroom is poisonous!
Again this test is not a reliable one. A good and reliable method is the use of a taxonomic
key, which can only be done by a specialist who understands the terminology of the fungi.
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Figure 5. Typical poisonous mushroom. A=Basidiocarp. B=Annulus. C=Volva. D=Stalk
At this point, it will interest us in knowing that lichen, which we shall treat in our next
lecture, is not a single organism, but a symbiotic association between a fungus
(ascomycetes) and certain green algae or photosynthetic bacteria (Cyanobacteria).
Besides, there are also members of basidiomycetes that form associations with green
algae, but they are not lichen.
Forms/Habits of fungi
Fungi life form is either saprophytic or parasitic.
1. Hyphae
2. Mycelium
3. The fruiting body (mushroom)
Habitats of fungi
Fungi mode of nutrition could either be saprophytic or parasitic. The latter fungi feed on
living organisms while the former concentrate on dead organisms is causing accelerated
A
B C
D
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decomposition. The saprophytic fungi are found generally on woods in varying stages of
decomposition.
Ecology of fungi
It is essential to know that both fungi and bacteria are essential decomposers of our
natural ecosystems. They are vitally important as decomposers. The fungi are majorly
terrestrial organisms, which share characteristics with both plant and animal. They are
heterotrophic, obtaining their food by external digestion using a powerful enzyme and
subsequently absorbing the nutrients. Fungi vital function is to close the gaps of many
nutrients cycle and recycle vital elements (nitrogen and phosphorus) back into the
ecosystems.
Economic uses of fungi
Fungi are beneficial to global ecosystems. Many forms are pathogenic (disease-causing).
They have their positive and negative benefits. It will surprise us that the positive benefits
could exceed the negative ones.
Positive benefits of fungi
1. The yeast strains cause the fermentation of grains and grapes in the making of beer and wine and in rising of bread dough
2. Penicillium spp. is a valuable source of the antibiotic penicillin growing on stale bread and fruit
3. Few basidiomycetes, mushrooms (umbrella-shaped), truffles (underground tuber), chanterelles (yellowish) and boletus (pore-like surface) are edible
4. Androstenol extracted from truffles, similar to a pheromone secreted by an animal, is added to certain cosmetics to attract the opposite sex
5. Ergot fungus (Claviceps purpurea) is a good source of ergotamine, which a. Enhances muscle and blood vessel constriction b. Relieves the horrible pain of migraines, c. Stimulates uterine contraction during childbirth and d. Prevents haemorrhaging
6. some mushrooms took as healing and preventive medicines a. some fungi used for longevity and spiritual energy (in China) b. eating mushroom improves blood circulation, reduce cholesterol level, lower
blood pressure, and boost the immune system c. some fungi have antitumor properties d. some fungi used to treat diabetes and cancer e. certain fungi enhance sexual energy f. certain fungi activate disease-engulfing macrophages and production of helper T-cells
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Negative benefits of fungi
Some fungi species are destructive and disease-causing. The class Deuteromycetes (imperfect fungi) includes several disease-causing species of humans. Such diseases include
Aspergillosis of the respiratory tract
Athlete's foot
Ringworm
Deposited toe and fingernails Other fungi can attack the cellulose acetate of colour transparencies and film
They contaminate food products (pieces of bread and canned foods)
They stained (etch) glass lenses as they grow
Deadly species contain dangerous neurotoxins
Conclusion
This lecture is an eye-opener to the world of fungi, which many of us always ignore. By
now, we must have learnt how to recognise the common fungi and where to find them.
Fungi have not fully utilised. This observation is as a result of a lack of interest in the
study of Botany and inadequate funding for research.
Summary
Having studied this lecture note, we should have:
1. some understanding of poisonous and non-poisonous fungi
2. a better idea of the characteristics that separate them from plant and animal
3. getting ready to look around our environment for the common fungi
4. better awareness of the uses of fungi
References/Further readings
Sumbali G., Johri B. M. (2005). Class Basidiomycetes. In Johri B. M.(Ed). The Fungi.
Narosa Publishing House. New Delhi India.132-168.
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CLASSCODE: DEPT.: MATRIC NO.:
Tutorial-marked questions
1. What is Androstenol? Explain its uses ___An extract from fungus (Truffles) ___Added to some cosmetics ___To attract opposite sex mates
2. State the popular mode of nutrition in fungi.
___Saprophytic mode and
___Parasitic mode
3. All mushrooms are poisonous. True or false.
___False
4. Give pieces of evidence to support the claim that fungi are neither plant nor animal
___They share characteristics of both plant and animal
___Plant characteristic include cellulose cell walls
___Animal characteristic include Chitin cell walls