Download Document

Kingdom Plantae
• Nonvascular and
Seedless Vascular Plants
Plants: General Features
• Sporic
meiosis
• General
Life
Cycle.
Fig.
37.3
Plants: Where from?
• Green algae: One line of green algae
gave rise to all plants
Fig.
32.12
Plants: Where from?
• Green algae. One line of green algae
gave rise to all plants
• Plantae is monophyletic kingdom.
Fig.
37.2
Kingdom Plantae
• Today we focus on phyla grouped into:
• Nonvascular plants
– Plants, but lack true (lignified) vascular tissue
• Seedless vascular plants
– Plants that have true vascular tissue (phloem and xylem),
but reproduce only by spores (no seeds made)
• Note that all the plants discussed today make
swimming sperm (they must swim through a film
of water to reach an egg). Sexual reproduction
requires moist conditions!
Kingdom Plantae
• Nonvascular plants
– Phylum Bryophyta (mosses)
– Phylum Hepaticophyta (liverworts)
– Phylum Anthocerophyta (hornworts)
Moss
Hornwort
Liverwort
Nonvascular plants: general features
• Lack true (lignified) vascular tissues
–
–
–
–
Leaf: flat structure containing vascular tissue
So, mosses lack true leaves. Make “leaf”
Stems: requires vascular tissue too
So, mosses lack stems. Make “stem”.
Nonvascular plants: general features
• Gametophyte dominant (photosynthetic)
– Most of life spent here!
– Sporophyte partially dependent on gametophyte
during development.
Phylum Bryophyta (mosses)
• Largest group of nonvascular plants (10,000
species)
• Gametophytes have “leaves” and “stems”
(lack vascular tissue)
• Make multicellular rhizoids that anchor
plant to ground (these NOT roots: lack
vascular tissue, don’t absorb much water).
Phylum Bryophyta (mosses)
• Life cycle: the
movie!
• Starring:
– Breye O’Fyte as
the gametophyte
– Spoh Rangium as
the capsule
QuickTime™ and a Cinepak decompressor are needed to see this picture.
Gametophyte/sporophyte relations
• So, vertical stalked
structures on
gametophytes are the
second generation in life
cycle (sporophytes)
• Note sporophytes grow
on and are at least partly
dependent upon
gametophyte
• “Deadbeat sporophytes”,
unable to live
independent lives.
Fig. 37.4
Moss importance
• Can be important producers in some habitats
• Economic importance: peat moss!.
Peat moss
• Dried or partially decomposed gametophytes of
Sphagnum.
Sphagnum gametophytes
Peat moss
• Sphagnum grows in wet areas called bogs (very
acid soil, water-logged, little decomposition).
Aerial (left) and ground (above)
views of bogs
Peat moss
• Dead Sphagnum builds up as peat
• Abundant: about 1 billion acres of peat bogs in
world (northern hemisphere mostly)
• 1% of Earth’s land surface!.
Peat moss
• Peat moss used as soil
amendment or potting
mix (good waterholding capability)
• Harvesting peat is
important industry in
northern temperate
zone (Canada,
Denmark, Sweden, etc.)
• Industry worth many
millions of dollars a
year.
Harvesting peat moss
Step1: Bogs are wet:
must ditch them to
drain them
Step 2: drying top layer
Step 3: Vacuum up
the dried moss
Peat bogs as archeological sites
• Bodies buried in bogs are often wellpreserved (“Bog people”).
• Allow archeologists to study vanished
societies.
A Book about
Bog People
Tollund man (Denmark):
Dated to around 0 AD
Grabaulle man (Denmark):
Dated to around 300 AD
Wooden wheel from
a bog dated 2700 BC
Phylum Hepaticophyta (liverworts)
• Fairly large (6,000 species)
• Two groups:
– 1) Leafy liverworts (look like mosses, but have
unicellular rhizoids). Most of these tropical,
many are epiphytes (grow on other plants).
Leafy liverworts on tropical tree
leaf
Leafy liverwort
Phylum Hepaticophyta (liverworts)
• Two groups:
– 2) Thallose liverworts. Simple flattened bodies.
Occur locally (emphasized in lab).
Thallose liverworts
Phylum Hepaticophyta (liverworts)
• Thallose liverwort life cycle: similar to moss, in that
gametophyte is major phase
• Sporophyte smaller and dependent on gametophyte.
Phylum Hepaticophyta (liverworts)
• But two small differences from
moss:
– antheridia on stalked structure
called antheridiophore
– archegonia on stalked structure
called archegoniophore.
Phylum Hepaticophyta (liverworts)
• Note that asexual production
can also occur via gemmae
(made in gemma cups)
• When splashed out by rain
drop, can grow by mitosis to
new gametophyte.
Close-up of gemmae in cup
Low power
view
Phylum Anthocerophyta (hornworts)
• Small group (100 species)
• Gametophytes look like thallose liverworts, but
sporophytes larger, photosynthetic, and less dependent
on gametophyte
• Green vertical structures below are sporophytes
growing out of gametophytes.
Kingdom Plantae
• Seedless vascular plants
–
–
–
–
–
Phylum Psilophyta (whisk ferns)
Phylum Lycophyta (club mosses)
Phylum Sphenophyta (horsetails)
Phylum Pterophyta (ferns)
Several other phyla that are now extinct (but
had glorious fossil past)
Seedless Vascular Plants (SVPs)
• General features:
• Sporophyte is dominant generation and can
grow independent of gametophyte (no more
“deadbeat sporophytes”!)
• Gametophytes small, reduced
• As with nonvascular plants, SVP
gametophytes can grow independent of
sporophyte.
Seedless Vascular Plants (SVPs)
•
•
•
•
General features:
Have cuticle, stomata
Have vascular tissue (phloem and xylem)
Thus, can make true leaves, stems, and roots.
Seedless Vascular Plants (SVPs)
• 2 kinds of leaves
– 1) microphyll: an epidermal outgrowth supplied by a vein
of vascular tissue
– 2) megaphyll: a reduced branch system that has become
flattened with photosynthetic tissue between branches.
Evolution of microphyll
(simple leaf)
Evolution of megaphyll
(complex leaf)
Kingdom Plantae
• Seedless vascular plants
–
–
–
–
–
Phylum Psilophyta (whisk ferns)
Phylum Lycophyta (club mosses)
Phylum Sphenophyta (horsetails)
Phylum Pterophyta (ferns)
Several other phyla that are now extinct (but
had glorious fossil past)
Phylum Psilophyta (whisk ferns)
• Small group (about 6 species)
• In lab, will see Psilotum
• Simple sporophyte bodies: just
stems. No leaves or roots
• Stems with dichotomous
branching (evenly split into
two smaller stems).
Psilotum branches
dichotomously (lumps
are sporangia)
Psilotum
growing
in crack
of rock
Phylum Psilophyta (whisk ferns)
• Sporangia on aerial stems
• Underground stems called
rhizomes: have filamentous
rhizoids.
Closed (top) and
split (bottom)
sporangia on stem
Phylum Lycophyta (club mosses)
• Second largest SVP group (1,100 species)
• Sporophytes with true leaves (microphylls),
roots, stems.
Isoetes
Lycopodium
Selaginella
Phylum Lycophyta (club mosses)
• Sporangia produced on
leaves called sporophylls
• Sometimes sporophylls
clustered into a group
called strobilus.
Phylum Lycophyta (club mosses)
• Interesting genera:
– Lycopodium
– Some native to
pitcher plant bogs in
Southeast U.S.
Pitcher plant bog
Lycopodium in bog
Phylum Lycophyta (club mosses)
• Interesting genera:
– Selaginella
– One desert species called
resurrection plant
– Rolls into ball as it dries,
when moistened unfurls and
can grow again.
Resurrection plant,
Selaginella lepidophylla
Phylum Lycophyta (club mosses)
• Interesting genera:
– Isoetes
– Small genus. Some
southeastern species are
endangered
– Grow in pools of water
on granite outcrops
(like Stone Mtn GA).
Phylum Lycophyta (club mosses)
• Interesting genera:
– Granite outcrops as
scattered habitat “islands”
– Two Isoetes species found
only in granite outcrop
pools, vulnerable to
human disturbance.
Isoetes
melanospora, an
endangered
species
Phylum Sphenophyta (horsetails
and scouring rushes)
• Small group: 1
genus (Equisetum)
with 15 species
• Make true stem
(hollow), roots,
leaves (small, may
be reduced
megaphylls) on
sporophyte.
Phylum Sphenophyta (horsetails
and scouring rushes)
• Gametophytes small
(several mm long), green,
independent of
sporophyte.
Phylum Sphenophyta (horsetails
and scouring rushes)
• Horsetails with whorls of side branches
• Scouring rushes lack side branches.
Scouring
rush
Horsetail
Phylum Sphenophyta
• Sporangia on underside of stalked structures called
sporangiophores
• Clustered in strobilus at stem tip.
Phylum Pterophyta (ferns)
• Largest SVP group (11,000 species)
• Mainly tropical, but many in temperate zone
• Make true leaves (megaphylls), stems, roots
on sporophyte
• Gametophytes small, delicate, independent
of sporophyte.
Fern
gametophytes
Phylum Pterophyta (ferns)
• Sporangia often on underside of leaves
• If in patch, patch called sorus (plural: sori)
• Some patches covered with tissue (indusium).
These sori are
uncovered (naked)
Each sorus here covered by
indusium
Phylum Pterophyta (ferns)
• Closeup of sorus with indusium (rounded
structures are sporangia).
Phylum Pterophyta (ferns)
• Life Cycle Movie:
QuickTime™ and a Cinepak decompressor are needed to see this picture.
Phylum Pterophyta (ferns)
• Fern Importance:
– Ornamental plants (indoor and outdoor).
Birdnest fern
Maidenhair fern
Frilly boston fern
Lady fern
Phylum Pterophyta (ferns)
• Fern Importance:
– Primary producers (important part of biomass of
some habitats).
Fern forest in Tasmania, Australia
Phylum Pterophyta (ferns)
• Fern Importance:
– Some are invasive exotics (non-natives that become
weeds): example, Japanese climbing fern in SE U.S.
– Like kudzu, climbs on and shades other plants.
Kingdom Plantae
• Seedless vascular plants
–
–
–
–
–
Phylum Psilophyta (whisk ferns)
Phylum Lycophyta (club mosses)
Phylum Sphenophyta (horsetails)
Phylum Pterophyta (ferns)
Several other phyla that are now extinct (but
had glorious fossil past)
Extinct SVPs and Their Importance Today
• Dominated land during Carboniferous
Period (354-290 million years ago)
– Coal swamps full of extinct plants
– Reconstructions below based on fossils
from coal.
Fossil Seedless Vascular Plants
(SVPs)
• Coal is incompletely decomposed carbon from
ancient plants (burns!).
Fossil SVPs
• Coal:
– Vital source of energy today!.
Coal seam
in western
U.S. desert
• Coal:
Fossil SVPs
– Vital source of energy today! (“Fossil fuel”)
– >50% of U.S. electricity.
Mining coal for power
Fossil SVPs
• Most important economically of all
Nonvascular Plants and SVPs
– Vital source of energy today!
Setting the stage for pollen/seeds
• Land plants have
specialized
gametes (egg,
sperm). Sperm
must swim in
water to reach
egg.
• Land plants have
specialized
gametangia
(antheridia and
archegonia).
Setting the stage for pollen/seeds
• Most of plants
discussed so far
do not have
specialized
gametophytes
• They are
homosporous
plants: make one
kind of
meiospore.
Setting the stage for pollen/seeds
• Heterosporous plants: make 2 types of
meiospores.
– One becomes male gametophyte and makes sperm
– One becomes female gametophyte and makes eggs
• Thus, make specialized spores and specialized
gametophytes.