Comprehensive Study Guide on Spore-Bearing Higher Plants

System of Higher Plants and Taxonomical Classification

The system of higher plants is primarily categorized based on their reproductive units into two main groups: those that reproduce via seeds and those that reproduce via spores. Higher plants (referred to as a group, not a single system) are divided into spore-bearing plants (Sporophyta) and seed-bearing plants (Spermatophyta). The taxonomical classification of the sub-kingdom of higher plants starts with the spore-bearing divisions, which include Ryniorasty (Rhyniophyta), Machorasty (Bryophyta), Plavúňorasty (Lycopodiophyta), Prasličkorasty (Equisetophyta), and Sladičorasty (Polypodiophyta). Within the Bryophyta, there are three distinct classes: Pečeňovky, Rožteky, and Machy.

Seed-bearing plants (Spermatophyta) encompass several divisions including Lyginodendrorasty, Kordaitorasty, Cykasorasty, and Borovicorasty (gymnosperms). The Borovicorasty are further classified into classes such as Ginká and Ihličnany, with the latter containing orders like Borovicotvaré, Cyprusotvaré, Tisotvaré, and Tisovcotvaré. The final major division is Magnoliorasty (angiosperms), which consists of two classes: Jednoklíčnolistové (monocotyledons) and Dvojklíčnolistové (dicotyledons). The monocots include families like Lipnicovité, Ľaliovité, Arekovité, and Vstavačovité. The dicots are much more diverse, including families such as Ružovité, Bôbovité, Ľuľkovité, Mrkvovité, Hluchavkovité, Astrovité, Lipovité, Kapustovité, Čajovníkovité, Mrlíkovité, Pŕhľavovité, Marenovité, and Kakaovníkovité.

Rhyniophyta: The Ancestors of Vascular Plants

The division Rhyniophyta consists of extinct, fossilized plants that represent a critical evolutionary step from thalloid algae to higher plants. These organisms thrived during the Silurian and Devonian periods, primarily in the Northern Hemisphere, where they formed dense growths up to $3\,m$ tall in shallow waters and on muddy shores. Their phylogenetic significance lies in their role in the evolution of all higher plants. A primary representative is Rhynia major, which possessed leafless stems or small veinless leaves. The plant stood between $20-50\,cm$ high.

The sporophyte of Rhyniophyta was characterized by rhizomoids instead of true roots and dichotomously branched (vidlicovito rozkonárené) stems known as mesomes (mezómy). The ends of these branches were called telomes (telómy), which could be either sterile or fertile. Fertile telomes carried the sporangia (výtrusnica). These plants underwent assimilation across the entire body surface and produced spores of identical shape (rovnaký tvar). From these spores, gametophytes grew; their thalli were morphologically similar to the sporophyte, but they developed gametangia instead of sporangia. Another notable representative, Psillophyton dapsile, was characterized by epidermal structures. Historically, these plants contributed to the formation of fossil fuels such as black coal and oil.

Bryophyta: Anatomy and Alternation of Generations

Machorasty (Bryophyta) are the oldest terrestrial plants, with fossil records dating back to the Paleozoic era. They are descendants of Rhyniophyta and are multicellular, eukaryotic organisms. Their cell walls contain cellulose without incrustations. Being green and autotrophic, their primary assimilation product is starch ($C_6H_{10}O_5$ in polymer form). They lack a sophisticated vascular system, instead transporting nutrients and water via osmosis and diffusion. Their body, a thallus, can be leaf-like (lupeňovitá) in lower forms or differentiated into rhizoids (pakorienky), cauloids (pabyľka), and phylloids (palístky). Unlike higher plants, phylloids grow around the cauloid rather than in a single plane. The base of the moss plant typically dies off while the apex continues to grow.

Bryophytes exhibit a distinct alternation of generations where the gametophyte ($n$) significantly predominates over the sporophyte ($2n$). This makes them unique among plant groups. The haploid gametophyte is evergreen and develops from a single-celled spore. In a suitable environment, the spore germinates into a green protonema (prvoklík), from which buds grow into either monoecious (jednodomé) or dioecious (dvojdomé) moss plants. Fertilization requires water (such as dew), where flagellated antherozoids (spermatozoidy) swim toward the archegonia (zárodočníky). The resulting diploid sporophyte remains attached to and dependent on the gametophyte. It consists of a seta (stopka) and a sporangium (výtrusnica). Inside the sporangium, diploid spore-producing tissue undergoes meiosis to produce haploid spores.

Classes and Diversity of Mosses

There are approximately $25,000$ species of mosses divided into three classes. The first class, Pečeňovky (Hepaticopsida), features thalloid or leafy bodies and cells rich in essential oils (silice). Their male sporangia are disk-shaped, while female ones are star-shaped. Representatives include Porastnica mnohotvará, found in wet areas, and Lupeňovec kužeľovitý. The second class, Rožteky (Anthocerotophyta), is phylogenetically the oldest and lives in symbiosis with cyanobacteria (sinice), often appearing on tree bark, with the genus Anthoceros sp. as a primary example.

The third class, Machy (Muscopsida or Bryopsida), features a differentiated thallus with rhizoids, cauloids, and phylloids. Their leaves contains two types of cells: chlorocytes, which contain chlorophyll for photosynthesis, and hyalocytes, which are empty and serve as water reservoirs. A key representative is Rašelinník močiarny (Sphagnum palustre), which grows in bogs and wet meadows. As the basal parts die and decay, they form layers of peat (rašelina). Other representatives include Merík vlnkatý (Mnium undulatum), found near streams; Ploník borievkový (Polytrichum juniperinum), which forms grey-green cushions on dry soils; Bielomach sivý (Leucobryum glaucum); Katarínka vlnkatá (Atrichum undulatum); and Dvojhrot chvostovitý (Dicranum scoparium).

Lycopodiophyta: The Clubmosses

Plavúňorasty (Lycopodiophyta) evolved from Rhyniophyta during the Late Silurian and Devonian periods. While modern species are herbaceous, fossil forms from the Carboniferous and Permian were massive trees reaching $20-30\,m$ in height. The stems are solid, dichotomously branched, and densely covered with small, single-veined leaves. On the upper side of the leaves, there is a small structure called a ligule (pajazýček) used for absorbing rainwater. Sporangia are located individually on the base of the upper side of sporophylls, often organized into spikes (klasy). These plants can produce either equal spores (isosporous) or different spores (heterosporous). The prothallium (prvoklík) develops into a gametophyte (prvorast). Historically, they were essential for forming oil and coal deposits.

In the class Lycopodiopsida, Plavúň obyčajný (Lycopodium clavatum) is a protected species with creeping stems and branches ending in two sporangial spikes; it prefers acidic soils in coniferous forests. The class Sellaginellopsida includes heterosporous types and includes the order Lepidodendrales. These were fossil trees like Lepidodendron and Sigillaria that grew up to $30\,m$ tall with thick, scarred trunks. They thrived in swampy, prehistoric jungles. A modern herbaceous representative is Plavúnka brvitá (Selaginella selaginoides), which is small ($8-10\,cm$) and found in mountain meadows.

Equisetophyta: The Horsetails

Prasličkorasty (Equisetophyta) also evolved from Rhyniophyta and peaked during the Carboniferous period. Today, they are perennial herbs characterized by adventitious roots and underground rhizomes. Their stems are segmented (článkované), whorled-branched (praslenovito rozkonárené), hollow, and ribbed. The cell walls are reinforced with silica ($SiO_2$). Vascular bundles are arranged in a ring around a central cavity and are hadrocentric (drevostredné). Leaves are simple, scale-like, and fused at the base into sheaths (pošvy). Sporangia grow on peltate (shield-shaped) sporangiophores clustered into terminal spikes.

Horsetails often exhibit two types of stems: a brown, fertile spring stem (jarná byľ) and a green, sterile summer stem (letná byľ) dedicated to photosynthesis. Spores are spherical and green, equipped with four ribbon-like elaters (rozhadzovače) for dispersal. The class Equisetopsida includes the fossil order Calamitales (e.g., Calamites), which reached heights of $20-30\,m$ and trunks $1\,m$ thick. Modern species belong to the order Equisetales, such as Praslička roľná (Equisetum arvense), which is used for medicinal purposes like treating urinary tract infections or hair loss. Other species include Praslička lesná (Equisetum sylvaticum), Praslička močiarna (Equisetum palustre), and the large Praslička obrovská (Equisetum talmetia).

Polypodiophyta: The Ferns

Sladičorasty (Polypodiophyta) comprise approximately $10,000$ species, predominantly herbs but including some woody species. They have rhizomes densely covered with roots. Their leaves, often referred to as megaphylls or trophosporophylls, are large, pinnately compound, and exhibit circinate vernation (spiral unfurling when young). They are often covered with trichomes. Sporangia are located on the underside of the leaves, usually grouped into clusters called sori (sorusy), which may be protected by a thin membrane called an indusium (zásterka). Prothallia are typically leaf-like and green. Fossil sub-classes like Protopteridiidae (e.g., Protopteridium, Cladoxylon) had shrub-like growth and dichotomous stems.

The class Polypodiopsida (Sladiče or Paprade) is the most numerous. Key representatives include Papraď samčia (Dryopteris filix-mas), which has leaves up to $1\,m$ long and sori with kidney-shaped indusia; its rhizome is used against intestinal parasites. Papradka samičia (Athyrium filix-femina) has finer leaves and is used ornamentally. Perovník pštrosí (Matteuccia struthiopteris) has distinct fertile and sterile leaves. Sladič obyčajný (Polypodium vulgare) features round sori without indusia. Other notable species include Slezinník červený, Jelení jazyk, and Orličník obyčajný which can have leaves up to $2\,m$ long. The tallest modern fern is the New Caledonian fern, reaching up to $10\,m$. The division also includes aquatic ferns from the sub-classes Marsileidae (e.g., Marsilea štvorlistá) and Salviniidae (e.g., Salvínia plávajúca), where some leaves are metamorphosed into root-like structures.