Pteridophyte Biology and Life Cycles

Vocabulary flashcards covering the classification, morphology, and reproductive life cycles of Pteridophytes, specifically focusing on Nephrolepis and Selaginella.

Pteridophytes

A group of plants where the sporophyte stage is more conspicuous than the gametophyte stage and which possess vascular bundles.

Prothallus

The independent gametophyte phase of pteridophytes, such as in Nephrolepis, which represents an advancement over bryophytes.

Psilotopsida

A class of pteridophytes that includes only two living genera: Psilotum and Tmesipteris.

Sphenopsida

A class represented by only one living genus, Equisetum, and approximately $18$ extinct forms such as Calamites and Annularia.

Nephrolepis

A genus in the family Polypodiaceae that survives in tropical and temperate regions, characterized as the sporophyte phase of the plant.

Rhizomes

Short underground stems that can make pteridophytes perennials by forming new leaves every year.

Homosporous

A condition where a plant produces only one type of spore.

Heterosporous

A condition where a plant produces two types of spores, often seen in aquatic types and Selaginella.

Sporophyllous

Leaves that bear spores and possess stomata.

Abaxial

The front section of the leaf.

Adaxial

The back side of the leaf, which in Nephrolepis contains brown spots called sori.

Sorus

A brown spot on the adaxial part of the leaf that contains the sporangium.

Archisporal cells

Primitive cells that undergo mitotic division to form spore mother cells.

Stomium

The structure that bursts to release spores which eventually germinate to form the prothallus.

Circinate vernation

The coiled arrangement of young leaves, common in ferns like Dryopteris.

Selaginella

A genus in the class Lycopsida that grows dichotomously and is found in moist areas of tropical and temperate zones.

Rhizophore

A structure that grows from the base of the dichotomous branching in Selaginella and bears fibrous roots.

Strobilus

An aggregation of leaf structures at the apex of dichotomous branching that contains spores and is photosynthetic.

Microspores

Small spores produced in the microsporangium that produce male gametes.

Megaspores

Large spores produced in the megasporangium that produce female gametes.

Selaginella Megasporangium Development

A process where $15$ of the $16$ megaspores die, and the remaining one undergoes meiosis to form four spores.

Microsporangium Spore Count

The structure where $16$ mother cells undergo meiosis to produce a total of $64$ spores.

Lycopsida Leaf Types

Includes large leaves growing from the base in two rows and small leaves growing on top of the large leaves, also in two rows.

Ploidy of a Zygote

The diploid state, represented as $2n$, which begins the sporophyte phase after fertilization.

Ploidy of a Spore

The haploid state, represented as $n$, marking the first stage of the gametophyte phase.