Seedless vascular plants Lecturer: Asst. Prof. Dr. İsmail EKER

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 Microphylls are thought to have evolved as extensions of stems Megaphylls are thought to have evolved from stem branchings that filled in with an additional webbing and perhaps in response to decreases in carbon dioxide 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 cone-like 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 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 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 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=005316198eb62a7e41225f403876574741477d763b247b6e576b34272c5f7b3d6d3f4e4b34a5a98a896 http://www.geog.ucsb.edu/events/department-news/1104/nineteen-species-of-fern-named-for-lady-gaga/