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The Seedless Vascular Plants: Ferns and Their Relatives Chapter 21.

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Presentation on theme: "The Seedless Vascular Plants: Ferns and Their Relatives Chapter 21."— Presentation transcript:

1 The Seedless Vascular Plants: Ferns and Their Relatives Chapter 21

2 Outline  Introduction  Phylum Psilotophyta – The Whisk Ferns  Phylum Lycophyta – The Ground Pines, Spike Mosses and Quillworts  Phylum Equisetophyta – The Horsetails and Scouring Rushes  Phylum Polypodiophyta – The Ferns

3 Introduction  During early stages of vascular plant evolution: Internal conducting tissue developed True leaves appeared Roots functioning in absorption and anchorage developed Gametophytes became progressively smaller  4 phyla of seedless vascular plants: Psilotophyta, Lycophyta, Equisetophyta, Polypodiophyta

4 Introduction  Psilotophyta Sporophytes without true leaves or roots Stems and rhizomes fork evenly  Lycophyta Plants covered with microphylls - leaves with single vein whose trace not associated with leaf gap Psilotum Lycopodium

5 Introduction  Equisetophyta Sporophytes with ribbed stems containing silica Whorled, scalelike microphylls lacking chlorophyll  Polypodiophyta Sporophytes with megaphylls - leaves with >1 vein and leaf trace associated with leaf gap −Often large and divided Equisetum A fern

6 Phylum Psilotophyta – The Whisk Ferns  Resemble small, green whisk brooms  Structure and form: Sporophytes: −Dichotomously forking stems  Above ground stems arise from rhizomes −Lack leaves and roots

7 Phylum Psilotophyta – The Whisk Ferns  Structure and form cont’d.: Sporophytes: −Enations - tiny, green, superficially leaflike, veinless, photosynthetic flaps of tissue −Roots, aided by mycorrhizal fungi, scattered along rhizomes

8 Phylum Psilotophyta – The Whisk Ferns  Reproduction: Sporangia fused in 3s and produced at tips of short branches Gametophytes develop from spores beneath ground −Branch dichotomously −No chlorophyll −Rhizoids aided by mycorrhizal fungi −Archegonia and antheridia scattered on surface Zygote develops foot and rhizome Rhizome separates from foot

9 Phylum Psilotophyta – The Whisk Ferns  Reproduction cont’d.:

10 Phylum Psilotophyta – The Whisk Ferns  Fossil whisk fern look-alikes Silurian, 400 mya −Cooksonia and Rhynia  Naked stems and terminal sporangia Devonian, mya −Zosterophyllum  Naked stems and rounded sporangia along stem  Thought to be ancestral to club mosses

11 Phylum Lycophyta – The Ground Pines, Spike Mosses, and Quillworts  Collectively called club mosses 2 living major genera −Lycopodium −Selaginella 2 living minor genera Several genera became extinct about 270 mya  Sporophytes have microphylls  Have true roots and stems

12 Phylum Lycophyta  Lycopodium - ground pines Often grow on forest floors Stems simple or branched −Develop from branching rhizomes Leaves usually < 1 cm long Roots develop along rhizomes

13 Phylum Lycophyta Sporangia in axils of sporophylls - sporangium-bearing leaves −Some species have sporophylls with no chlorophyll, are smaller than other leaves and clustered into strobili (singular: strobus ) In sporangia, sporocytes undergo meiosis, producing spores  Lycopodium reproduction:

14 Phylum Lycophyta  Lycopodium reproduction cont’d.: Gametophyte

15 Phylum Lycophyta  Selaginella - spike mosses Abundant in tropics Branch more freely than ground pines Leaves with ligule on upper surface

16 Phylum Lycophyta  Selaginella reproduction: Produce 2 different kinds of gametophytes = heterospory −Microsporophylls bear microsporangia containing microsporocytes, producing tiny microspores - becomes male gametophyte, consisting of antheridium within microspore wall −Megasporophylls bear megasporangia containing megasporocytes, producing 4 large megaspores - develops into female gametophyte consisting of many cells inside megaspore  Several archegonia produced where spore wall ruptures

17 Phylum Lycophyta  Selaginella reproduction cont’d.:

18 Phylum Lycophyta  Isoetes - quillworts Found in areas partially submerged in H 2 O for part of year Microphylls arranged in tight spiral on stubby stem Ligules occur towards leaf bases Corms have vascular cambium Plants generally > 10 cm tall

19 Phylum Lycophyta  Isoetes reproduction: Similar to spike mosses, except no strobili Sporangia at bases of leaves

20 Phylum Lycophyta  Ancient relatives of club mosses and quillworts: Dominant members of forests and swamps of Carboniferous, 325 mya −Large, tree-like, up to 30 meters tall - Lepidodendron Surface of Lepidodendron, showing microphyll bases

21 Phylum Equisetophyta – The Horsetails and Scouring Rushes  Equisetum  Branched and unbranched forms, usually > 1.3 m tall  Stems jointed and ribbed If branched, branches in whorls Scalelike leaves in whorls at nodes Stomata in grooves between ribs

22 Phylum Equisetophyta  Stem anatomy: Hollow central cavity from break down of pith Two cylinders of smaller canals outside pith − Carinal canals - conduct H 2 O with xylem and phloem to outside − Vallecular canals - outside carinal canals contain air Silica deposits on walls of stem epidermal cells

23 Phylum Equisetophyta

24  Equisetum reproduction: Asexual by fragmentation of rhizomes Sexual reproduction: −Strobili at tips of stems with sporangia connected to sporangiophores −Spores green with 4 elaters attached −Gametophytes lobed, green, cushion-like, up to 8 mm in diameter Spores with elaters

25 Phylum Equisetophyta  Equisetum reproduction cont’d.:

26 Phylum Equisetophyta  Ancient relatives of horsetails: Flourished in Carboniferous, 300 mya  Human and ecological relevance: Many giant horsetails used for food by humans and other animals Scouring rush stems used for scouring and sharpening Reconstruction of fossil giant horsetail, Calamites

27 Phylum Polypodiophyta – The Ferns  Structure and form: Vary in size from tiny floating forms < 1 cm to giant tropical tree ferns up to 25 m tall −Fern leaves are megaphylls - fronds  Typically divided into smaller segments −Require external H 2 O for reproduction

28 Phylum Polypodiophyta – The Ferns  Reproduction: Sporophyte conspicuous phase −Fronds, rhizomes, roots −Fronds first appear coiled in crozier, and unroll and expand  Fronds divided into segments called pinnae (singular: pinna) Crozier

29 Phylum Polypodiophyta – The Ferns  Reproduction cont’d.: Sporangia stalked −Scattered on lower leaf surface, confined to margins, or found in discrete clusters called sori (singular: sorus)  Sori may be protected by indusia (singular: indusium) −With row of heavy- walled, brownish cells = annulus Sorus covered by indusium

30 Phylum Polypodiophyta – The Ferns  Reproduction cont’d.: Meiosis forms spores in sporangia Spores released and grow into gametophytes called prothalli (singular: prothallus) Prothalli one cell thick, and have archegonia and antheridia Zygote develops into young sporophyte Gametophyte dies and leaves sporophyte growing independently

31 Phylum Polypodiophyta – The Ferns  Reproduction cont’d.:

32 Phylum Polypodiophyta – The Ferns  Fossil relatives of ferns: Devonian, 375 mya - possible ancestors of ferns – Resemble ferns in growth habit, but look more like whisk ferns Possible ancestors: Aglaophyton and Psilophyton

33 Phylum Polypodiophyta – The Ferns  Fossil relatives of ferns cont’d. Carboniferous, mya - tree ferns abundant −Seeds found on some of fossil tree ferns

34 Phylum Polypodiophyta  Human and ecological relevance: House plants −Function well as air filters Outdoor ornamentals Cooked rhizomes as food Folk medicine Fronds used in thatching for houses. Basketry and weaving

35 Review  Introduction  Phylum Psilotophyta – The Whisk Ferns  Phylum Lycophyta – The Ground Pines, Spike Mosses and Quillworts  Phylum Equisetophyta – The Horsetails and Scouring Rushes  Phylum Polypodiophyta – The Ferns


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