Tracheophytes Monilophyta

Embryophyte Relationships

• Categories of Embryophytes:

  • Liverworts

  • Mosses

  • Bryobiotina

  • Hornworts

  • Tracheophyta

    • Includes groups with proper vascular systems:

      • Lycopodiophyta

      • Euphyllophyta

      • Monilophyta

      • Spermatophyta

Monilophyta: Ferns & Horsetails

• Characteristics:

  • Vascular plants with megaphylls

  • Disperse by spores

  • Includes:

    • Horsetails

    • Ferns

    • Whisk ferns

    • Psilotum

• Genetic Relationships:

  • Still being sorted

• Reproductive Structures:

  • Produce antheridia and archegonia

  • Require water for flagellated sperm

  • Majority are homosporous

Primitive versus Advanced Groups of Monilophytesquisetopsida - Horsetails

• General Facts:

  • 15 – 25 living species and hybrids

  • All in a single genus, Equisetum

  • Global distribution

  • Typically < 1m tall but some tropical species >4.5m tall

  • Accumulate silica in stems, known as 'scouring rush'

  • Sporophyte dominant

Horsetail Sporophyte Structure

• Composition:

  • Ribbed, jointed photosynthetic stems arise from branching rhizomes with roots at nodes

  • Branches arise in regular whorls along the stem

  • Sporangia located on strobilus at the top of the shoot.

Horsetail Leaves

• Leaves are reduced and fused into a toothed whorl

• Photosynthesis largely conducted by stem and branches

• Leaves arise from nodes along the stem

Equisetum Characteristics

• Physical Features:

  • Clearly ribbed/ridged stems

  • Well-developed cuticle

  • Stomata located in grooves

Horsetail Anatomy & Ecology

• Vascular system supports colonization of drier habitats compared to Bryophytes

• Fossil horsetails were arboreal (tree-like)

• Air canals in stems/roots allow rooting in marshy soils

• Rhizomes facilitate quick ground colonization

Horsetail Reproduction

• Characteristics:

  • Homosporous

  • Sporangia produced on strobili, which consist of multiple sporangiophores

  • Each sporangiophore bears 5-10 sporangia

• Spores:

  • Produced by meiosis, each featuring 4 appendages

  • These appendages are elaters, and they are haploid

Equisetum Gametophyte Development

• Spores travel through the air to land on soil; germinate within a week

• Gametophytes develop rhizoids to anchor in soil

• Initially, male and female gametophytes are produced, with unfertilized females later producing antheridia to ensure fertilization

• Sperm swim towards archegonia in wet conditions

Life Cycle of Equisetum

• Sequence: Fertile shoot -> Vegetative Strobilus shoot -> Sporophyte -> Sporangium -> Gametophyte

• Fertilization occurs leading to a diploid zygote

Equisetum and Human Uses

• Uses include:

  • Dye

  • Scouring agents

  • Sharpener material

  • Edible parts

  • Diuretics

  • Contribution to coal, gas & oil deposits

Fern Classification and Characteristics

• Taxonomy currently in flux

• Closely related horsetails and whisk ferns sometimes included

• Two primary groups:

  • Polypodiopsida:

    • Most commonly referred to as ferns

    • Vascular tissues present

    • Megaphylls (mostly pinnate)

    • Homosporous (except Salviniales)

  • Marratiopsida:

    • Approximately 130 species of primitive ferns

Polypodiopsida Class and Characteristics

• 7 Classes Include:

  • Osmundales (Royal ferns)

  • Hymenophyllales (Filmy ferns)

  • Gleicheniales (Tropical)

  • Schizaeales (Southern hemisphere)

  • Salviniales (Aquatic)

  • Cyatheales (Tree ferns)

  • Polypodiales (Most Irish species)

Fern Structure and Function

• Fronds detach and develop from the tip of the rhizome as tightly rolled coils

• Fronds are characterized by complex vascular systems

• Fertile fronds produce sporangia in clusters called sori

Ferns in Reproduction

• Sporangia: Found on undersurfaces of the fronds, grouped in sori

• Mature sporangia produce haploid spores by meiosis

• Released spores germinate into a gametophyte, which has rhizoids and no vascular tissues

• Sperm travel to fertilize eggs in the archegonia

Life Cycle of Ferns

• Fertilized egg develops into diploid sporophyte

• Sperm are guided to archegonia by chemical attractants

• Diploid embryo forms roots and fronds, growing into the sporophyte stage

Ophioglossum and Botrychium

• Ophioglossum vulgatum: 1 of 25-30 species in the order Ophioglossales

• Botrychium lunularia: 1 of 30-40 species; taxonomy remains unclear

Phylum Psilotophyta - Whisk Ferns

• Relationships & Classification:

  • Confused taxonomy, superficially similar to early fossil plants

  • Now considered part of the ferns

• Genera Include:

  • Psilotum:

    • 2 species

      • Psilotum nudum

      • Psilotum complanatum

  • Tmesipteris:

    • 13 species

Psilotophyta Characteristics

• Dominant sporophyte consists of evenly forking green stems without true leaves/roots

• It features scale-like outgrowths called enations

Psilotum Reproductive Structures

• Sporangia are axillary and grouped into synangia (3 sporangia fused)

• All spores produced are identical (homosporous)

Gametophyte Development in Psilotum

• Mature gametophytes are brown, cylindrical and radially symmetrical

• Grow underground and covered with rhizoids, sometimes associating with fungi

Human Relevance of Whisk Ferns

• Minimal economic importance

• Historical uses in Hawaii for laxatives and treating rashes

• Horticultural interest in Japan with significant breeding history

Summary of Embryophytes

• Two major vascular systems:

  • Bryobiotina (No proper vascular system) with microphylls and megaphylls

  • Tracheophytes (Proper vascular system) with seeds and spores, including heterospory and homospory in varying distributions.