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Transcript
Seedless Vascular Plants Plant Diversity May 7th, 2009 Tracy Bucannon Alyxis Feltus Nathaniel Guimon 4 Phyla of Seedless vascular plants Lycophyta y p y Sphenophyta horsetails Pterophyta club moss, spike moss, quillworts ferns Psilotophyta Whisk ferns Seedless vascular plants They y are true vascular plants p because they y have xylem and phloem. Unlike the bryophytes, the sporophyte is the dominant generation and the gametophyte is very small. Although these plants once dominated the earth, they now make up only 5% of living plant species. species Ferns (Pterophyta) Most ferns are homosporous (one kind of spore) p ) The gametophyte ge e at o iss generation small in comparison to the sporophyte sporophyte, is heart shaped, and asexual. Ferns Ferns are the earliest g group p of p plants to have leaves with highly branches vascular systems (megaphylls). Ferns are the only group of seedless vascular plants that have megaphylls Megaphylls occur in All seed plants Parts of a Fern Frond Sori Pinnae Fiddlehead (young leaf) Rachis Rhizome Phylum Psilotophyta: Whisk Ferns The vast majority of psilotophytes belong to the genus Psilotum, which contains 129 species i off whisk hi k ferns. f Most are found in ttropical i l and d subtropical bt i l regions of Asia and Americas. They frequently grow as weeds in greenhouses. Leaves Unlike other vascular plants they have no true roots or leaves Enations: the stem has small scale like, small, like nonvascularized flaps of ggreen tissue Enations Stems The photosynthetic, whisklike stem bear trilobed, yellow sporangia, usually along the sides of th stem the t Branching pattern is called: bifurcation Psilotum have a protostele There is no difference between below-ground vascular structure and stem vascular structure Roots Nutrients are absorbed by rhizomes that have rhizoids, or root hair like structures lik In the mature sporophyte, a photosynthetic branching stem system forms buds on rhizomes Buds on Rhizomes Reproductive system Psilotum is homosporous and the gametophyte is bisexual Spores p (n) ( ) Sporangia The Th spores are also l exosporic (spores are released outside) The spores are located inside the Sporangium, the sporangia is formed as yellow tri-lobed knobs on the stems Stem Enations Tri- lobed Sporangia Life cycle: Whisk fern Phylum Sphenophyta: Horsetails The only living genus is Equisetum, consisting of 15 species commonly known as horsetails. Horsetails are practically i di ti indistinguishable i h bl from f fossils 400 million years old. Commonly known as “scouring rushes” Body structure Equisetum q differs from that of the other ferns allies in having jointed and ribbed stems with the leaves arranged in whorls at the nodes Microphyllsp y leaves arranged in whorls at the nodes The leaves are known as microphylls Microphylls feel somewhat rough b because their h i epidermal id l cells contain silica Ribbed stems with joints Stem Photosynthesis takes place l iin stem t off the th Equisetum sporophyte Hollow stem The Th sporophyte h has h a hollow, jointed stem with whorled microphylls at the nodes The vascular cambium produces secondary xylem but no secondary phloem Vascular Bundles Reproductive Cycle sporangiophor e Strobilus Sporangia are clustered into umbrellalike sporangiophores that are grouped together geometrically into a strobilus Each E h spore are wrapped with elongated structures called elaters,, which uncoil as the strobilus matures and dries, dispersing the spores Each germinating spore develops within a few weeks into an independent, independent photosynthetic gametophyte that is typically bisexual Equisetum Gametophyte Male Antheridium Female Archegonium Lycophyta True: roots,, stems,, leaves 1,000 species Difficult to find Subterranean 3 orders Isoetes: Quillwart Lycopodiales: Club Moss Selagnillales: Resurrection Plant Club Moss Isoetes: Quillwort Dichotomous branching g 60 species Only genus with vascular cambium Heterosporous Microsporangium Longitudinal section of Isoetes rhizophore Megasporangium Lycopodium: Club Moss Microphyll p y leaves 200 species (mostly tropical) Sporangia located at the base Gametophyte Archegonia Antheridia Club Moss: Continued Lycopodium y p strobilus Sporangium Sporophyll Selaginella: Spike Mosses Most M li live in i tropical i l environments i Some desert (Resurrection Plant) 700 species Endosporic -gametophyte gametophyte development within spore wall Selaginella lepidophylla Resurrection Plant Selaginella: Spike Mosses Ability y to resurect Selaginella strobilis megaspores microspores microsporangium megasporangium Thanks for listening. listening Any questions?
