Plant Diversity 1: Seedless Plants

Comprehensive vocabulary flashcards covering the evolutionary origins, derived synapomorphies, life cycles, anatomy, and ecology of seedless plants, including bryophytes, lycophytes, and monilophytes.

Archaeplastida

The eukaryotic supergroup that includes green algae and land plants, which colonized land approximately $470\text{ mya}$.

Cuticle

A waxy layer covering the epidermis of land plants that functions to reduce water loss and protect against desiccation.

Stomata and Guard Cells

Microscopic pores in the epidermis flanked by specialized regulatory cells that open and close to manage gas exchange and transpiration.

Apical Meristems

Localized regions of active cell division located at the growing tips of roots and shoots that allow elongation and primary growth.

Sporangia

Multicellular plant organs in which diploid sporocytes undergo meiosis to generate walled, haploid spores.

Alternation of Generations

A reproductive life cycle in which a multicellular haploid gametophyte ($n$) phase alternates with a multicellular diploid sporophyte ($2n$) phase.

Gametophyte

The haploid ($n$) multicellular stage in a plant's life cycle that produces haploid gametes through mitosis.

Sporophyte

The diploid ($2n$) multicellular stage in a plant's life cycle that produces haploid spores through meiosis.

Bryophytes

The collective term for nonvascular land plants (mosses, liverworts, and hornworts) characterized by a life cycle dominated by the gametophyte generation.

Phylum Bryophyta

The phylum of nonvascular plants comprising true mosses, with approximately $15{,}000$ known species.

Phylum Hepatophyta

The phylum of nonvascular plants comprising liverworts, with approximately $9{,}000$ known species.

Phylum Anthocerophyta

The phylum of nonvascular plants comprising hornworts, with approximately $100$ known species.

Protonema

A mass of green, branched, threadlike haploid filaments produced by germinating moss spores that develops 'buds' which grow into gametophytes.

Rhizoids

Tubular single cells or filaments of cells that anchor nonvascular plants to substrate without serving a primary role in water or nutrient absorption.

Archegonia

Female gametangia in plants that produce and retain a single non-motile egg cell and shelter the resulting embryo.

Antheridia

Male gametangia in plants that produce and release flagellated sperm cells that require moisture to swim.

Foot (Bryophyte)

The basal region of the bryophyte sporophyte that remains embedded in the maternal archegonium to absorb nutrients.

Seta

The elongate stalk of a bryophyte sporophyte that elevates the capsule and conducts nutrients from the gametophyte.

Capsule (Bryophyte)

The terminal sporangium of a bryophyte sporophyte where meiosis produces haploid spores for dispersal.

Peristome

A ring of tooth-like structures around the opening of a moss capsule that regulates the gradual release of spores according to environmental moisture.

Peat

Thick layers of partially decayed organic matter formed by mosses like Sphagnum in waterlogged, acidic bog environments, storing significant global carbon.

Xylem

Vascular tissue composed of cells that are dead at functional maturity, specialized for transporting water and dissolved minerals and providing structural rigidity via lignin.

Phloem

Vascular tissue consisting of living cells (including sieve-tube elements and companion cells) that transports sugars and other photosynthetic products.

Lignin

A durable organic polymer that embeds within cell walls of vascular plants to provide structural rigidity, mechanical support, and height.

Microphylls

Small, unbranched leaves supported by only a single strand of vascular tissue, unique to lycophytes.

Megaphylls

Leaves supported by a highly branched vascular network, providing greater surface area for photosynthesis in ferns, gymnosperms, and angiosperms.

Sporophyll

A modified, specialized leaf that bears sporangia for spore production.

Sori

Clusters of sporangia located on the undersurface of fern sporophylls.

Strobili

Cone-like reproductive clusters formed by groups of closely packed sporophylls, common in many lycophytes and gymnosperms.

Fern Frond

The large leaf of a fern sporophyte, typically divided into a stalk (stipe) and multiple leaflets (pinnae), growing from an underground rhizome.

Fern Gametophyte

A tiny, independent, photosynthetic, typically heart-shaped haploid structure that anchors by rhizoids and bears antheridia and archegonia.

Homosporous Spore Production

The production of a single type of spore by one type of sporophyll, typically developing into a bisexual gametophyte producing both eggs and sperm.

Heterosporous Spore Production

The production of two distinct types of spores (megaspores that produce female gametophytes and microspores that produce male gametophytes) by different sporophylls.

Phylum Lycophyta

A phylum of seedless vascular plants consisting of club mosses, spikemosses, and quillworts (~$1{,}200$ extant species) that possess microphylls.

Phylum Monilophyta

A phylum of seedless vascular plants comprising ferns, horsetails, and whisk ferns (~$12{,}000$ extant species) that possess megaphylls.

Carboniferous Period

A geologic period dating from $359\text{--}299\text{ mya}$ during which dense forests of lycophyte trees, horsetails, and ferns accumulated without being decomposed by fungi, resulting in massive coal formations.