Transcript Understanding Our Environment

Introduction to the Plant Kingdom:
Bryophytes
Outline
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Introduction
Phylum Hepaticophyta - Liverworts
Leafy Liverworts
Phylum Anthocerophyta - Hornworts
Phylum Bryophyta - Mosses
Features of the Plant Kingdom
A. General Characteristics
1. Major pigments (chlorophylls a and b)
2. Starch as reserve food product
3. Cellulose in cell walls
4. Phragmoplasts and cell plate
5. Fatty cuticle
6. Stomates
B. Reproduction
1. Mostly sexual reproduction although asexual forms occur
2. Gametangia protected from desiccation
3. Embryos formed
4. Distinct alternation of generations
Introduction to the Bryophytes
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About 23,000 species of bryophytes.
 Include mosses, liverworts, and hornworts.
 Habitats range in elevation from sea level up to
5,500 meters or more.
 Small, low-to-the-ground plants, moist shaded
habitats.
 Bryophytes of all phyla often have mycorrhizal
fungi associated with their rhizoids.
 In some instances, fungi apparently are at least
partially parasitic.
Introduction to the Bryophytes
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Peat mosses are ecologically important in bogs.
Luminous mosses are found in caves and in other
dark, damp places.
None have true xylem or phloem.
 Many have hydroids (xylem-like) and leptoids
(phloem-like).
Exhibit alternation of generations.
- Gametophyte, the green leafy generation.
- Sporophyte produces spores, grows from tip of
leafy gametophyte.
Phylum Hepaticophyta - Liverworts
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Structure and Form
- Most common liverworts have flattened,
lobed thalli.
 Gametophyte stage develops from
spores.
 When spores germinate they may
produce immature gametophyte
(protonema).
Phylum Hepaticophyta
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Thalloid Liverworts
 Best known species are in the genus
Marchantia.
- Thick thallus that forks dichotomously as
it grows.
 Consists of parenchyma cells with
few, if any, chloroplasts.
Fig. 20.4
Section of Marchantia Thallus
Reproduction in Marchantia
Sexual
a. Male and female gametophores produce antheridia and
archegonia
b. Flagellated sperm fertilize egg in archegonium
c. Embryo (immature sporophyte) develops
d. Sporophyte consists of foot, seta, and capsule
e. Meiosis takes place in the capsule
f. Capsule decays and spores aided in their release by
spiral shaped elaters
Asexual
gemmae cups separate from parent thallus
Marchantia Sporophyte
Asexual Reproduction of Marchantia
Leafy Liverworts
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Always have two rows of partially
overlapping “leaves” whose cells contain
distinctive oil bodies.
 Often have folds and lobes.
Archegonia and antheridia are produced in
cup-like structure.
 At maturity, sporophyte capsule may be
pushed out as the seta elongates.
- Germinating spore produces a
protonema.
Fig. 20.8
Phylum Anthocerophyta
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Hornworts
 Structure and Form
- Mature sporophytes look like miniature
greenish-blackish rods.
 Only about 100 species worldwide.
 Thalli have pores and cavities filled
with mucilage, that often contain
nitrogen-fixing bacteria.
Fig. 20.9a
Hornworts
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Asexual Reproduction
 Fragmentation
 Separation of lobes from main thallus.
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Sexual Reproduction
 Archegonia and antheridia are produced in rows
beneath the upper surface of the gametophytes.
 Have both unisexual and bisexual plants.
 Sporophyte develops from zygote, has numerous
stomata.
 Meiosis takes place in sporophyte “horn”
 Spores released when sporophyte tip splits open
in longitudinal segments.
Hornwort Sporophyte
Phylum Bryophyta
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Mosses
 Structure, Form, and Classes
- About 15,000 species of mosses
currently known.
 Divided into three classes:
 Peat Mosses
 True Mosses
 Rock Mosses
Fig. 20.10
Mosses
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“Leaves” of moss gametophytes have no
mesophyll tissue, stomata, or veins.
 Blades are nearly always one-cell thick,
and are never lobed or divided.
 Initially formed in three ranks and usually
end up appearing to be arranged in a spiral
or alternately on an axis that twists as it
grows.
Sexual Reproduction in Mosses
1. Female gametangium are called the archegonium (flask
shaped)
2. Male gametangium are called the antheridium (club
shaped)
3. Gametangia produced at tips of leafy gametophytes
4. Sperm are flagellated and reach archegonium by swimming
in a film of water
5. Sporophyte develops in base of archegonium and grows
into a foot, seta, and a capsule
6. Calyptra sits on top of capsule
7. Meiosis takes place in the capsule producing spores
8. Peristome teeth at rim of capsule aid in dispersal of spores
9. Spores germinate on moist soil and develop into an algallike protonema
10. Protonema develops tiny "leafy" buds which will produce
the upright gametophytes
Asexual Reproduction in Mosses
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Fragments of leaves, stems, and rhizoids
can develop protonema.
Phylum Bryophyta
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Human and Ecological Relevance
 Pioneer Species of Primary Succession. Rapidly colonize bare or
burned soil.
 Indicators of Surface Water
 Packing Material
 Peat Mosses
- Soil Conditioner: retention of water in dead, empty cells (1
kilogram of dry peat moss will take up 25 kilograms of water)
- Antiseptic (antibiotic) properties: The natural acidity produced
inhibits bacterial and fungal growth and gives.
- Because of its water absorbing ability and antispetic
characteristics, peat moss was used in dressing wounds (poultice
material) in World War I.
- Fuel
- Peat deposits harvested and burned in stoves.
- Peat smoke used to flavor Scotch whisky.
Review
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Introduction
Phylum Hepaticophyta - Liverworts
Leafy Liverworts
Phylum Anthocerophyta - Hornworts
Phylum Bryophyta - Mosses
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