Botany and Mycology: Plant Evolution, Seed Plants, and Fungal Diversity

Comprehensive vocabulary flashcards covering the evolutionary history, structure, life cycles, and terminology of early land plants, seedless vascular plants, gymnosperms, angiosperms, and the fungal phyla.

Sporic Life Cycle (Alternation of Generations)

The life cycle exhibited by land plants in which a multicellular haploid gametophyte generation alternates with a multicellular diploid sporophyte generation.

Gametophyte

The haploid ($1n$), gamete-producing generation in the plant life cycle that is dominant in non-vascular plants (bryophytes).

Sporophyte

The diploid ($2n$), spore-producing generation in the plant life cycle that develops from repeated mitotic divisions of a zygote and is dominant in vascular plants.

Antheridium

The multicellular, sperm-producing male gametangium found in algae, bryophytes, and seedless vascular plants.

Archegonium

The multicellular, egg-producing female gametangium found in early land plants where fertilization occurs.

Bryophytes

A group of non-vascular embryophytes comprising three monophyletic phyla (liverworts, mosses, and hornworts) with approximately $19{,}000$ characterized species where the gametophyte ($1n$) is the dominant generation and the sporophyte is dependent.

Phylum Marchantiophyta

The liverwort phylum (also known as Hepaticophyta) characterized by a thallus and rhizoids, with male and female gametophytes producing antheridiophores and archegoniophores.

Gemmae Cups

Cup-like structures on the thallus surface of certain liverworts such as Marchantia polymorpha that function in asexual reproduction.

Phylum Anthocerophyta

The hornwort phylum, in which the antheridia and archegonia are located on the surface of the thallus and the sporophyte forms an elongate horn-like structure containing a columella and pseudoelaters.

Lycophylls

Small leaves with a single unbranched strand of vascular tissue found in the lycophytes.

Psilotum nudum

A whisk fern within the pteridophytes that features forked photosynthetic stems bearing sporangia and lacks true roots and leaves.

Sori (singular: Sorus)

Clusters of sporangia located on the undersides of mature fern sporophyte leaves (fronds).

Prothallus

The small, typically heart-shaped, independent photosynthetic gametophyte of a fern anchored to the substrate by rhizoids and bearing antheridia and archegonia.

Sporopollenin

A durable, resistant biological polymer that coats plant spore walls, protecting early land plant fossils dating back to $420\text{--}430\text{ MYA}$.

Lepidodendron

An extinct genus of giant lycophyte from the Carboniferous period ($354\text{--}290\text{ MYA}$) that could reach heights of up to $40\text{ meters}$ ($131\text{ feet}$).

Calamites

An extinct genus of giant horsetail from the Carboniferous period that grew to almost $20\text{ meters}$ ($66\text{ feet}$) in height.

Medullosa

A genus of extinct seed ferns from the Carboniferous period that produced seeds roughly the size of walnuts.

Euphylls (Megaphylls)

Broad leaves with branched vascular systems that evolved from ancestral branch systems that flattened and filled in with photosynthetic tissue.

Gymnosperms

Vascular seed plants with 'naked seeds' that develop exposed on the surfaces of scales or leaves rather than enclosed within fruits, and produce secondary wood via vascular and cork cambium meristems.

Phylum Cycadophyta

A phylum of approximately $300$ species of gymnosperms commonly known as cycads (including Zamia roezlii) producing distinct male and female cones and flagellated sperm large enough to be seen without magnification.

Ginkgo biloba

The sole surviving species of the gymnosperm phylum Ginkgophyta, characterized by fan-shaped leaves and fleshy seeds.

Welwitschia mirabilis

A gnetophyte species found in Namibia with a deep taproot that produces only two permanently growing leaves and acquires water from coastal fog.

Phylum Coniferophyta (Pinophyta)

The most diverse gymnosperm group, producing microsporangia on pollen cones and megasporangia on woody ovule cones.

Angiosperms

Vascular plants with 'enclosed seeds' that produce flowers, fruits, and triploid endosperm, comprising Dicotyledones (about $75\%$), Monocotyledones ($23\%$), and magnoliids and minor groups ($<2\%$).

Perianth

The non-reproductive sterile envelope of a flower consisting collectively of the calyx (sepals) and corolla (petals).

Exine

The tough, decay-resistant outer wall layer of a pollen grain composed of sporopollenin.

Intine

The inner wall layer of a pollen grain composed primarily of cellulose and pectins.

Micropyle

A small opening in the integuments at the apex of an ovule through which the pollen tube enters to reach the embryo sac.

Double Fertilization

A reproductive process unique to angiosperms where one sperm fertilizes the egg to form a diploid ($2n$) zygote, and a second sperm fuses with the two polar nuclei of the central cell to produce triploid ($3n$) endosperm.

Anemophily

The pollination syndrome characterized by the dispersal of pollen by wind currents.

Melittophily

The pollination syndrome in which flowers are specialized for pollination by bees.

Chiropterophily

The pollination syndrome in which flowers are adapted for pollination by bats.

Wolffia borealis

A tiny aquatic angiosperm (duckweed) whose miniature floral cavity contains only one pistil and one stamen, making it smaller than a grain of table salt.

Supergroup Opisthokonta

The eukaryotic supergroup that includes Kingdom Fungi and Kingdom Animalia along with related protists such as Nuclearia.

Chitin

A tough, nitrogenous polysaccharide comprising the fungal cell wall, structured as a long-chain polymer of N-acetylglucosamine with the formula $(C_8H_{13}O_5N)_n$.

Hyphae

The individual microscopic, branching filaments that make up the vegetative body (mycelium) of a fungus.

Septate Hyphae

Fungal hyphae partitioned into cellular compartments by internal cross-walls known as septa.

Aseptate Hyphae

Coenocytic fungal hyphae that lack cross-walls, resulting in continuous cytoplasmic tubes containing multiple nuclei.

Plasmogamy

The stage of fungal sexual reproduction in which the cytoplasm of two compatible mating gametangia or hyphae fuse without the immediate fusion of their nuclei.

Karyogamy

The fusion of two haploid nuclei within a dikaryotic or heterokaryotic fungal cell to form a diploid ($2n$) zygotic nucleus.

Dikaryotic Stage ($n + n$)

A phase in the life cycle of higher fungi (ascomycetes and basidiomycetes) where hyphal cells possess two genetically distinct haploid nuclei per compartment following plasmogamy.

Phylum Zygomycota

A fungal phylum of approximately $665$ species with aseptate hyphae (such as the black bread mold Rhizopus stolonifer) that form resting, thick-walled zygosporangia during sexual reproduction.

Phylum Ascomycota

The sac or cup fungi, a phylum containing approximately $30{,}000$ described species with septate hyphae that produce sexual spores inside microscopic sacs called asci.

Ascus (plural: Asci)

A microscopic sac-like sexual reproductive cell found in ascomycetes within which karyogamy and meiosis followed by one mitosis typically yield eight haploid ascospores.

Ascocarp

The multicellular, dikaryotic macroscopic fruiting body of an ascomycete fungus that bears asci.

Phylum Basidiomycota

The club fungi, comprising approximately $16{,}000$ described species of mushrooms, shelf fungi, puffballs, smuts, and rusts that form basidiospores on club-shaped cells called basidia.

Basidium (plural: Basidia)

A club-shaped microscopic terminal cell on the gills or pores of a basidiocarp where karyogamy and meiosis occur to produce four external haploid basidiospores.

Phylum Chytridiomycota

An early-diverging, primarily aquatic lineage of fungi commonly known as chytrids that produce flagellated zoospores.

Phylum Glomeromycota (AM Fungi)

A phylum of obligate fungal symbionts with aseptate hyphae that form arbuscular mycorrhizal associations by penetrating the root cortical cells of land plants.

Saprobes

Heterotrophic decomposer fungi that obtain nutrients by secreting enzymes to break down nonliving organic material, specifically recalcitrant substances like cellulose and lignin.

Ectomycorrhizae

Symbiotic associations between fungi and plant roots where fungal hyphae form an external mantle and grow between cortical cells without penetrating their plasma membranes.

Fungal Endophytes

Fungi that inhabit the internal tissues of plant leaves and stems without causing apparent disease, such as the endophytic fungi in fescue grasses that produce toxins causing fescue foot in cattle.

Lichen

A composite organism formed from a mutualistic symbiosis between a fungus (the mycobiont) and a photosynthetic partner (the photobiont), which can be a green alga or cyanobacterium.

Soredia

Small, wind-dispersed asexual reproductive propagules of lichens composed of clusters of algal or cyanobacterial cells enveloped in fungal hyphae.