Seedless vascular plants Lecturer: Asst. Prof. Dr. İsmail EKER.
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Transcript of Seedless vascular plants Lecturer: Asst. Prof. Dr. İsmail EKER.
Seedless vascular plantsLecturer: Asst. Prof. Dr. İsmail EKER
GENERAL CHARACTERISTICS OF SEEDLESS VASCULAR PLANTS
• 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
• Vascular tissue• leaves with waxy cuticles and stomata• depend on water for reproduction and nourishment• Sporophyte is dominant and can grow
independent of gametophyte
– Phylum Psilophyta (whisk ferns)– Phylum Lycophyta= Lycopodophyta (club mosses)– Phylum Sphenophyta= Equsetophyta (horsetails)– Phylum Pterophyta= Pterodophyta (ferns)
SYSTEMATICS OF SEEDLESS VASCULAR PLANTS
• 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
Pterophyta (ferns)
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).
Each sorus here covered by indusiumThese sori are uncovered (naked)
Closeup of sorus with indusium (rounded structures are sporangia).
Polypodium
Asplenium
• 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 cone-like strobilus
• Life cycle is similar to fern life cycle; also requires water
Stenophyta (horsetails)
• 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.
• 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!
Lycophyta (club mosses)
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.
Isoetes
• 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
Psilophyta (whisk ferns)
Psilotum branches dichotomously (lumps are sporangia)
Psilotum sp. growing in crack of rock
• 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 westernU.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• 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.geog.ucsb.edu/events/department-news/1104/nineteen-species-of-fern-named-for-lady-gaga/
http://www.ingentaconnect.com/content/aspt/sb/2012/00000037/00000004/art00002?token=005316198eb62a7e41225f403876574741477d763b247b6e576b34272c5f7b3d6d3f4e4b34a5a98a896
