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Home , Equisetales, Leptosporangiate fern, Psilotaceae, Sporophyll, Stele (biology), Xylem

Monilophytes

Fabulous

The Monilophyte Lineage

From Pryer et al. 2001

Leptosporangiate ferns

Monilophytes

Equisetaceae

Eusporangiate ferns

Seed

Lycophytes

1 Megaphylls Micro- vs. Mega-phyll Evolution

• gap • Microphyll: single, • More than 1 branched vein unbranched vein with no leaf gap (left side) • Telome theory of megaphyll • Megaphyll: Vein evolution branching multiple times with a leaf gap (right side) • Review microphyll evolution from lecture

Telome Theory of Megaphyll Eusporangium Evolution • (megaphylls) of arthrophytes, ferns & plants evolved from branch systems (telomes) by overtopping, planation & webbing

Found in most lineages

2 Leptosporangium Eusporangium Leptosporangium • Relatively large • Relatively small • Thick-walled • Thin-walled (1 - (several cell-layers) layer thick) • Many (100s- • (Usually) 64 spores 1,000s) • No specialized • Dehisce via annulus dehiscence mechanism • Stalked • No stalk • Form from just 1 • Form from several initial cell initial cells Only in the “true ferns,” Polypodiophyta

Location of Vascular The

• Evolutionary progression in complexity & • Arrangement (pattern) of location of vascular tissue (esp. stems) • & stem morphology usually different • Related to megaphyll development from each other – Large, numerous leaf traces = many large leaf gaps – How we can tell a is a modified stem, not • Location of stele = equilibrium between a root location of strengthening & conducting cells • Useful for distinguishing between different • Ideal location for strengthening tissue is just taxonomic groups beneath the surface of a cylindrical structure • , which do not produce leaves, have at the center of the axis the most simple stelar types & the stele is in – Least likely to break when stems are bent by wind the center of the axis – Mostly an Actinostele

3 Stele Types: Protostele Stele Types: Siphonosteles xylem phloem • Simplest type of stele • Xylem & phloem form • Solid core of xylem concentric cylinders surrounded by a cylinder of around central phloem • Ectophloic Osmunda • 3 general variations siphonostele: phloem pith • Haplostele: solid cylinder restricted to outer of xylem surface of xylem • Actinostele: radiating cog- • Amphiphloic like ridges of xylem siphonostele • Plectostele: cylindrical (solenostele): phloem xylem core with masses of phloem interspersed within found both external & internal to xylem stem Lycopodium

Siphonostele Types Psilotophyta: Psilotum

• Fault of leaves! – Don’t blame me Psilotophyta • Dictyostele: stele appears Psilotopsida as discrete strands or Psilotales bundles in cross section Psilotaceae Psilotum • Eustele: discrete strands, xylem inner & phloem outer (dicots) • Atactostele: bundles scattered, xylem/phloem random facing – Monocots

4 Psilophyta Morphology

• Until recently, though to be most primitive, • Naked stems extant lineage of vascular plants • Dichotomous branching • 2 genera • & – Psilotum (pantropical) – No true leaves or roots – Tmesipteris (New Zealand) • Homosporous – Enations • Cultivated in Japan for 400-500 years as an • Similar to , but: ornamental – Enations (leaf-like flaps of tissue) • Whiskferns – Sporangia axillary (not terminal) – Sporangia fused into synangium

Synangium

• 3 fused sporangia (in Psilotum) • Small • In axils of enations (axillary) • Subterranean • Lack – Mycotrophic – Depend on fungal partners for nutrition

5 Psilotum Stems Primitive Lineage?

• Many believe that Psilotum (& Tmesipteris) closest living relatives to Rhyniophytes. • BUT there are alternative hypotheses • Psilotophyta are highly modified group of ferns which have lost many fern-like characters Protostele (Actinostele) – Why? Large fossil gap; similarities • Chemical & morphological features suggest affinity with “eusporangiate”

Tmesipteris Ophioglossophyta Ophioglossophyta • Similar to Psilotum, but with leaf-like Ophioglossopsida structures Ophioglossales • Enations or flattened stem? Ophioglossum – Vascular tissue (rules against enation) Botrychium • Only 2 sporangia in synangium

Ophioglossum

6 Ophioglossophyta The Players

• Dimorphic fronds • Ophioglossum – Sporangia borne on fertile fronds – Adder’s-tongue ferns – Other segment is flattened & vegetative • Ophioglossum reticulatum has largest • Leaves are megaphylls known chromosome # (2n = 1,260!) • True roots – 84-ploid! • Homosporous – Haplopappus gracilis = lowest #, 2n = 4 • Gametophytes • Botrychium – Subterranean – Grape ferns; rattlesnake ferns – Lack chlorophyll – Mycotrophic

Equisetophyta: Equisetum

Equisetophyta • Horsetails, scouring rushes Equisetopsida • Near-cosmopolitan • Many fossil taxa – Up to large Equisetum • Dates back to • Toxins include nicotine & thiaminase (breaks down thiamine) • May help with Alzheimer’s

7 Equisetum Stem Equisetum Stem

• Jointed at nodes • 3 series of canals – Point of • Central (inner) attachment for – Aeration leaves & lateral • Carinal (middle) branches) – Associated with • Ridged (or ribbed) xylem & phloem • Accumulate silica – Opposite ridges in – Aids conduction • Vallecular (outer) • Photosynthetic – Alternate with – Leaves reduced ridges; function?

Strobilus & Sporangiophore Spores

• Elaters • Sporangia in – Modifications of outer • But in sporangiophores wall – Stem tissue, not • Dispersal sporophylls – Uncurl when dry – Peltate (umbrella-shaped) – Coiled when wet • Homosporous

8 Gametophyte Pteridophyta: “True” Ferns • Photosynthetic • Unisexual – but plant homosporous! • Sex due to environmental cues, e.g., light intensity, quality (e.g., red light) • Some female gametophytes exude a chemical that turns neighboring ones male

Phylogenetically Speaking Polypodiophyta Polypodiopsida Polypodiaceae sensu lato Many genera; Various families (we’ll put them just in this one for now) Osmunda Marsileaceae Marsilea Azolla Salvinia

9 Polypodiophyta General Morphology

• Date to (like & • Leptosporangiate eusporangiate Monilophytes) • Dictyostele • Abundant in (Pennsylvanian) • Leaves simple to compound • Modern fern genera date back to Tertiary & – Very variable across fern groups (not as old as extant lycophyte genera) – Megaphylls • Largest group of extant cryptogams (> • Circinate vernation 12,000 spp.) • Sporophyte dominant • Morphologically diverse – Free-living • Variety of habitats – Still require for fertilization

Circinate vernation Reproductive Morphology

• Distinctive uncoiling of young leaves • Mostly homosporous – Also in (convergence) • Sporophylls = megaphylls anatomically • Fiddleheads (or croziers) • Sporangia mostly in sori – Prior to uncoiling – Underside of leaves – That brown stuff that most people think is or dirt

10 Fern Sporangia Exindusiate

• Sorus: clusters of sporangia • Indusium: covering of sorus E.g., Phymatosorum • Annulus: specialized Indusium completely lacking dehiscence mechanism – Ring of thickened cells – Contract sharply when dry – Scatter spores

E.g., Platysereus Exindusiate

Peltate Sorus Reniform Sorus

Reniform: kidney-shaped Peltate indusium E.g., Cyrtonium

Peltate: umbrella-shaped

E.g., Nephrolepis

11 False Indusium Gametophyte

• Prothallus generally heart-shaped • Dorso-ventrally flattened

False indusium E.g., Adiantium

False indusium

Pteridophyte Life Cycle OK, So Where Are We?

Finished with these ones

12 Osmundaceae Osmundaceae

• Basal lineage – Lack of sorus – Primitive annulus – Molecular data • E.g., royal fern, cinnamon fern • Dimorphic leaves

– Separate fertile/sterile (cinnamon) Osmunda regalis (royal fern) – Both on one (royal)

Osmunda cinnamomea (cinnamon fern)

Heterosporous Water Ferns Marsileaceae

• ONLY heterosporous “true” fern lineage • Water clovers – Marsileaceae & Salviniaceae (sister groups) • Cosmopolitan in warm temperate & • Not particularly fern-like to look at tropical areas • Sporocarps: specialized adaptations to living in water – Modified sporophylls with tightly clustered sori; sporophyll fronds are hardened – Morphology varies across groups

Marsilea

13 Marsilea Sporocarp Sporocarps: Sorophore

• Paired at sterile leaf base • Sorophore: gelatinous backbone • Burst when hydrated – Swells when hydrated • Each sorus with micro- & mega – Sporangia attached sporangia Sorophore • Can keep spores viable up to 100 years – Adaptations for growth in arid regions? • Dispersed by waterfowl • Sporangia lacking annulus Sporocarp (burst) Sporocarps

Spores & Gametophytes Salviniaceae

• Megasporangia with just 1 • Salvinia – Megagametophyte with 1 – Floating ferns • with 16-64 – Microspores burst as sperm released • Gametophytes minute, endosporic • Azolla – Mosquito ferns

14 Salvinia Salvinia molesta

• Rootless • Giant Salvinia, from SE Brazil • 3 leaves • WORLDWIDE NOXIOUS WEED! – 2 floating, leaf-like – 1 pendant, root-like • Produce sporocarps

Salvinia molesta

• Aggressive weed with wide ecological tolerance • Very rapid growth • A single plant has been described to cover 40 square miles in 3 months! • Rapidly expanding populations can overgrow & replace native plants • Resulting dense surface cover prevents light Azolla & atmospheric from entering water • Decomposing material drops to bottom, consuming dissolved oxygen needed by fish & other aquatic life

15 Azolla: Mosquito Ferns

• 1 leaf with 2 lobes • Upper lobe houses Anabaena – Filamentous blue-green alga – Fixes atmospheric nitrogen • Was important in past rice crops – Fertilizer for rice plants – Still used in many places for same reason

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