Chapter 23 Lycophytes and Ferns SSI-1
Early Vascular Plants Chapter - 23: Lycophytes and Ferns
Page 1: Introduction to Early Vascular Plants
Overview of seedless vascular plants, focusing on lycophytes and ferns.
Page 2: Types of Vascular Plants
Nonvascular plants:
Liverworts (Marchantiophyta)
Hornworts (Anthocerophyta)
Mosses (Bryophyta)
Key characteristics: No vascular tissues, no true leaves, stems, or roots. Dominant gametophyte stage, sporophyte dependent on gametophyte, relies on water for reproduction.
Seedless vascular plants:
Lycophytes (Lycopodiophyta)
Ferns and their relatives (Pteridophyta)
Features include true vascular tissues, true stems and roots, independent gametophyte, and dominant sporophyte stage.
Page 3: Discussion on Complexity of Vascular Plants
Vascular plants considered more advanced and complex.
Key Characteristics:
Presence of vascular tissues (xylem and phloem).
True stems and roots.
Independent sporophyte generation.
Ability to grow larger and more structurally complex.
Use of spores for reproduction under water-dependent conditions.
Page 4: Classification of Vascular Plants
Vascular plants or eutracheophytes are categorized into two primary groups:
Seedless vascular plants
Seed-bearing vascular plants
Page 5: Characteristics of Early Vascular Plant Sporophytes
Sporophyte Body:
Increased size and branching
Became independent and dominant
Features multiple growth tips (apical meristem).
Produces multiple sporangia and relies on spores for dispersal.
Emergence of Vascular Tissues:
Introduction of lignified tracheids alongside the true stems and roots.
Example: Aglaophyton major, an ancient vascular plant.
Page 6: Evolution of Leaves in Vascular Plants
Leaves developed vascular tissues and exhibit determinate growth.
Arrangement on the stem is definite and can be classified into:
Microphylls: Unbranched vascular tissue.
Megaphylls (Euphylls): Branched vascular tissue.
Page 7: Types of Leaves
Microphylls:
Characteristics include a single vein and confusion in naming as it does not indicate size.
Megaphylls:
Have a complex branched vascular system.
Examples: Krauss’s spike moss and Tunbridge filmy fern.
Page 8: Sporophyll Definition
Sporophylls: Modified leaves that bear sporangia.
In ferns, sporophylls are normal foliage leaves.
In gymnosperms, they are modified to form cones (strobili).
In angiosperms, they transform into flowers.
Page 9: Spore Production Variations
Most seedless vascular plants are homosporous, producing one type of spore leading to bisexual gametophytes (e.g. prothallus).
Seed plants and some seedless plants are heterosporous, producing:
Megaspores: Female gametophytes.
Microspores: Male gametophytes.
Page 10: Overview of Seedless Vascular Plants
Categories:
Lycophytes: Includes club mosses, quillworts, and spike mosses.
Ferns and their relatives include ferns, horsetails, and whisk ferns.
Characteristics: True vascular tissues, true stems and roots, independent gametophyte.
Page 11: Characteristics of Lycophytes
Club Mosses:
Once large trees, now small perennial evergreen plants.
Not true mosses despite common naming conventions.
Key features include numerous small leaves and perennial growth habits.
Page 12: Quillwort Characteristics
Quillworts illustrate adaptations to their environment by growing from the substrate in which they are rooted, often appearing simple and quill-like.
Page 13: Lycopodium Features and Growth
Lycopodium: Ground pines that grow on forest floors, featuring simple or branching stems.
Leaves: Generally less than 1 cm long; roots develop along rhizomes.
Page 14: Vegetative Growth of Lycopodium
Dichotomous branching: Formation in Y-shapes, presenting many small microphylls which support a single vein of vascular tissue.
Page 15: Lycopodium Reproduction
Sporangia are located in the axils of sporophylls.
Features sporophylls, sporangia, and spores indicative of reproduction.
Page 16: Homosporous Nature of Lycopodium
Homosporous: Producing bisexual gametophytes, represented by a single type of spore developing into both male and female organs.
Page 17: Examples from Lycophyta
Key examples of species include Isoetes gunnii, Selaginella moellendorffii, and Diphasiastrum tristachyum represented visually.
Page 18: Heterosporous Features of Selaginella
Selaginella: Heterosporous; produces distinct megaspores and microspores along with their respective megasporangia and microsporangia.
Page 19: Heterosporous Life Cycle of Spike Moss
The heterosporous cycle leads to the formation of two distinct gametes, highlighting the adaptation of spike moss.
Page 20: Extinct Lycophyte Showcase
Extinct species like Lepidodendron and Sigillaria reached towering heights and contributed to significant ecological environments during their time.
Page 21: Phylum Monilophyta Overview
Distinguishing features of whisk ferns, being less leaf-like with tiny green outgrowths, and significant traits of modern ferns.
Page 22: Diversity of Ferns and Horsetails
Ferns: Most diverse in tropical regions and possess over 12,000 species.
Horsetails: Restricted to Equisetum, showcasing adaptation to moist environments.
Page 23: Features of Horsetails
Characteristics: Reduced megaphylls and silicate embedded stems used for scrubbing surfaces in historical contexts.
Page 24: Whorled Branches of Equisetum
Visualization of the Equisetum vegetative shoot, demonstrating either whorled branches or unbranched structures.
Page 25: Structural Close-up of Equisetum
Details of anatomy and growth patterns in Equisetum, emphasizing unique characteristics of its branches.
Page 26: Anatomical Highlights of Equisetophyta
Stem anatomy features a hollow cavity and a unique canal system facilitating water and air movement via silica deposits.
Page 27: Fern Stem Characteristics
Fern stems (rhizomes) typically grow underground, helping water absorption and structural stability.
Page 28: Fern Anatomy and Fiddleheads
Fern leaves are termed fronds; unique ‘fiddlehead’ emergence noted during growth phases.
Page 29: Structure of Fern Leaves
Features of sporophylls and their roles in reproduction noted in fern anatomy.
Page 30: Sori in Ferns
Sori: Clusters of sporangia on the leaf underside, often shielded by protective indusia.
Page 31: Lifecycle of Ferns
Diagrammatic representation showcasing the gametophyte stage, fertilization, and alternation of generations in ferns.
Page 32: Fern Gametophyte Development
Overview of process illustrating gametophyte functions and roles of antheridia and archegonia in reproduction.
Page 33: Fern Life Cycle Animation
Visual representation illustrating key phases in the alternation of generations within ferns.
Page 34: Prothallus Characteristics
Prothallus: Brief lifespan, small heart-shaped structure, critical in the life cycle, and formation of gametes.
Page 35: Whisk Fern Structure
Characterization of whisk ferns, lacking definitive leaves and relying on underground rhizome systems.
Page 36: Defining Tree Ferns
Characteristics of tree ferns, including their distinctive trunks and frond permanence despite season changes.
Page 37: Importance of Seedless Vascular Plants
Applications in horticulture, agriculture, medicine, and formation of coal.
Page 38: Azolla and Cyanobacterial Relationships
Azolla: Water fern with mutualistic cyanobacterium aiding in ecological fertilization processes.
Page 39: Additional Reading
Suggested textbook chapter for deeper understanding of seedless vascular plant importance to humans.
Page 40: Review Questions
Topics to cover include shared characteristics, ecological importance, differences between plant groups, life cycle identification, and features of Equisetum.
Page 41: Spores and Alternation of Generations
Highlight of the reproductive cycle showcasing the transition between diploid and haploid states.