Seedless vascular plants
Lecturer: Asst. Prof. Dr. İsmail EKER
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GENERAL CHARACTERISTICS OF SEEDLESS VASCULAR PLANTS
Vascular tissue
leaves with waxy cuticles and stomata
depend on water for reproduction and nourishment
Sporophyte is dominant and can grow
independent of gametophyte
• There are two types of leaves that may be found
on seedless vascular plants
– Microphylls
• Small and have a single vascular strand
– Club mosses, horsetails
– Megaphylls
• Larger and have more than one
vascular strand
• Plants needed a flattened blade
with more stomata for gas
exchange
– Ferns
SYSTEMATICS OF SEEDLESS VASCULAR PLANTS
– Phylum Psilophyta (whisk ferns)
– Phylum Lycophyta= Lycopodophyta (club mosses)
– Phylum Sphenophyta= Equsetophyta (horsetails)
– Phylum Pterophyta= Pterodophyta (ferns)
Pterophyta (ferns)
• Largest and most diverse SVP group
(12,000 species)
-Mostly terrestrial, Few are aquatic
• Mainly tropical, but many in temperate
zone
• Make true leaves (megaphylls), stems,
roots on sporophyte
- Have xylem and phloem tissue
• Gametophytes small, reduced,
independent
• sporophylls with spores arranged in sori
Fern
gametophyte
fiddleheads are young fronds; sori appear on the fronds and
house spores
The Sporophyte
continues to
grow while the
Gametophyte
dies.
Life cycle of Ferns
• Spores (n) germinate into a prothallus (n) which will produce
eggs (n) in the archegonium and sperm (n) in the antheridium
they combine to form a zygote (2n)
• the zygote grows into a young sporophyte (2n)
• the mature sporophyte of most ferns produce only one type
of spore (homosporous- one spore type produced and
released); some are heterosporous, that is they produce two
spore types, one developing into a male gametophyte, the
other into a female gametophyte
• Water is required for the sperm to use as a medium to swim
to the egg
• 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
Closeup of sorus with indusium (rounded structures
are sporangia).
Polypodium
Phyllitis
Adiantum
Asplenium
Azolla- aquatic fern
Stenophyta (horsetails)
• Once dominant plants in the landscape,
300my ago
• Equisetum (horsetail/scouring rush) only
living genus with 15 species
• True roots, stems and small leaves (reduced
megaphylls= microphylls); hollow jointed
stems impregnated with silica; green stem
main photosynthesizing part
• The silica gives horsetails a gritty texture
which American pioneers utilized as pot and pan
scrubbers
• Reproductive branches bear a terminal conelike strobilus
• Life cycle is similar to fern life cycle; also
requires water
• Gametophytes small (several mm
long), green, independent of
sporophyte.
• Sporangia on underside
of stalked structures
called sporangiophores
• Clustered in strobilus at
stem tip.
Some horsetails change their appearance between
spring and summer. Left: Horsetails in early spring make
and disperse spores Right: In late spring, bushy green
stems carry on photosynthesis.
Lycophyta (club mosses)
• Second largest SVP group – Club mosses, spike mosses, quillworts – 1200
spp.
• grew to 35m tall; some are epiphytes (on other plants), quillworts are
aquatic
• Sporophytes with branching stems and tiny, scale-like sterile leaves
(microphylls), roots
• Produce clusters of sporophylls (fertile leaves; spore-bearing leaves) called
strobilus (pl. strobili)
• Some are homosporous, some are heterosporous; If heterosporous, male
microspores (n) will be produced along with female megaspores (n); once shed,
these spores will develop into male and female gametophytes which will
produce sperm and egg respectively; when the egg is fertilized a sporophyte
(2n) will form; within the strobilus spores form and the process repeats
• Like ferns and horsetails, club mosses have both an asexual and sexual stage
in their life cycle. But the life cycle of a club moss may take as long as 15 years
to complete!
It is a small evergreen plant
that looked like the plant.
This plant has small
mosslike leaves that are
closely arranged on its
stem. On top of the plant is
a club-shaped structure.
For these reasons, this
plant is named a club
moss.
In fact, some club mosses
look so much like young
pine trees that people call
them ground pine.
• Sporangia produced on
leaves called sporophylls
• Sometimes sporophylls
clustered into a group
called strobilus.
Lycopodium
Selaginella
Isoetes
Psilophyta (whisk ferns)
• Small group (about 6 species) and Most are extinct
• Simplest vascular plants
• Very primitive vascular plant; simple sporophyte bodies: just erect
stems. No leaves or roots. They have absortive rhizoids with
mycorrhizae, stems, and leaflike structures
• Stems with dichotomous branching (evenly split into two smaller
stems). Consists of dichotomously branching rhizomes
• Stems are the main photosynthetic organ
Psilotum sp. growing in crack of rock
Psilotum branches dichotomously
(lumps are sporangia)
• Sporangia on aerial stems
• Underground stems called
rhizomes: have filamentous
rhizoids.
Closed (top) and split
(bottom) sporangia
on stem
Importance of Seedless Vascular Plants
• Roles in the Environment:
– Ferns, horsetails, and club mosses
help form soil
– Help prevent soil erosion
– Ferns can play a role in the
formation of communities in
rocky areas
– Primary producers (important part
of biomass of some habitats).
Fern forest in Tasmania, Australia
Economical importance: Fossil SVPs
• Coal: Eventually the pressure and heat changed the ferns and other
plants into coal, oil, and natural gas.
• Dominated land during Carboniferous Period (354-290 million years
ago)
– Vital source of energy today!
– Vital source of energy today! (“Fossil fuel”)
– >50% of U.S. electricity.Coal seam
in western
U.S. desert
Mining coal for power
• Coal is incompletely decomposed carbon from
ancient plants (burns!).
• The remains of ancient ferns, horsetails, and
club mosses formed coal.
– Fiddleheads of some ferns can be cooked and eaten
• Ferns and some club mosses are popular houseplants and floral
arrangements (indoor and outdoor).
• Horsetails are used in some dietary supplements, shampoos, and skin-care
products.
Maidenhair fern
Lady fern
KEYWORDS OF VASCULAR PLANTS
• Homospory
– The production of one
kind of spore
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Bryophytes
Whisk ferns
Horsetails
Most club mosses
Most ferns
– Spore gives rise to
gametophyte plants that
produce both egg and
sperm cells.
KEYWORDS OF VASCULAR PLANTS
II
• Heterospory
– Production of two kinds of
spores
• Microspores
– Give rise to male
gametophytes that produce
sperm cells
• Megaspores
– Give rise to female
gametophytes that produce
eggs.
– Occurs in
• Certain club mosses
• Certain ferns
• ALL SEED PLANTS.
– The “evolution” of heterospory
was an essential step in the
evolution of seeds.
Artist’s conception of a Carboniferous forest based on fossil evidence
Pop music megastar Lady Gaga is being honored with
the name of a new genus of ferns found in Central and
South America, Mexico, Arizona, and Texas in 2012. A
genus is a group of closely related species; in this case,
19 species of ferns will carry the name Gaga. At one
stage of its life, the new genus Gaga has somewhat fluid
definitions of gender and bears a striking resemblance to
one of Gaga's famous costumes. Two of the species in
the Gaga genus are new to science: Gaga germanotta
from Costa Rica is named to honor the family of the
artist, who was born Stefani Germanotta. And a newly
discovered Mexican species is being dubbed Gaga
monstraparva (literally monster-little) in honor of Gaga's
fans, whom she calls “little monsters.”
http://www.ingentaconnect.com/content/aspt/sb/2012/00000037/00000004/art00002?token=005316198eb62a7e4
1225f403876574741477d763b247b6e576b34272c5f7b3d6d3f4e4b34a5a98a896
http://www.geog.ucsb.edu/events/department-news/1104/nineteen-species-of-fernnamed-for-lady-gaga/