MEDICAL BOTANY - A.G. Serbin - 2003

SECTION 3. SYSTEMATICS

SUPERKINGDOM EUKARYOTA — EUCARYOTA. KINGDOM PLANTAE

SPORE-PRODUCING PLANTS

The evolutionary relationships of this plant group are illustrated in Figure 3.3. They are distinguished from higher seed plants by A number of characteristics:

✵ dissemination occurs via spores;

✵ The life cycle clearly exhibits Morphology/12.html">ALTERNATION OF GENERATIONS;

✵ the processes of sexual and asexual reproduction are separated: spores

_• are formed in the sporangia of certain plants—sporophytes, while Gametes are produced in the gametangia of other plants—gametophytes (see Fig. 2.1, 2.5);

✵ the male sex organ—the antheridium—contains numerous motile spermatozoa, whereas the female organ—the archegonium—contains a non-motile egg Cell;

✵ Fertilization requires liquid Water droplets;

✵ spores may be of one type (homosporous plants) or of two types—macro- and microspores (heterosporous plants);

✵ axial Organs lack secondary thickening due to the absence of secondary meristematic tissue—the cambium.

HIGHER SPORE PLANTS are subdivided into pre-SHOOT, non-vascular plants, which include the phylum Bryophyta, and shoot-bearing, vascular plants, encompassing three phyla: Lycopodiophyta, Equisetophyta, and Pteridophyta. They differ from bryophytes by the presence of true Vascular Tissues, roots, and leaves, and by the dominance of the sporophyte over the gametophyte in the life cycle.

PHYLUM BRYOPHYTA — BRYOPHYTA

Mosses comprise about 35,000 species characterized by a number of primitive vegetative Structure traits. For instance, they lack fully developed true vascular tissues (phloem and xylem); true roots are absent, with absorption being performed by rhizoids, or by the entire body surface if rhizoids are absent. The photosynthetic organs are leaf-like stem outgrowths known as phyllids, which lack true Veins. The gametophyte is dominant in the life cycle. It is represented by a protonema (primary protonema) developing from a spore, and gametophores arising from the protonema, which are monoecious or dioecious perennial herbaceous plants.

Mosses are widespread, preferring damp, non-saline substrates. Their ecological role lies in regulating the water balance, absorbing and retaining moisture, waterlogging soils, preventing soil erosion, protecting tree bark, pioneering bare substrates, and creating conditions for the growth of other plants. Mosses are capable of accumulating radioactive substances and heavy metals. Being hygroscopic and unpalatable to animals, they are used as litter. They can serve as an antiseptic dressing material. Certain mosses are utilized as fuel, building material, fertilizer, and for obtaining oxalic acid, furfural, etc.

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Class Leafy Mosses — Musci

Gametophytes are monoecious or dioecious perennial herbs forming turf mats. They may possess rhizoids (true mosses) or lack them (sphagnum mosses). Phyllids are alternate, veinless (sphagnum mosses) or with false veins (true mosses). Archegonia and antheridia are located at the apex of the shoot; sperm Cells are biflagellate. Egg fertilization occurs in the presence of moisture. A sporophyte develops from the zygote on the female gametophyte, consisting of a stalk-like sporogonium, or seta, and a sporangium in the form of a capsule with a lid (operculum) and a hairy calyptra. Morphologically identical + and − spores germinate into female and male filamentous or lamellar protonemata (pre-protonemata) bearing buds, from which new unisexual gametophytes grow.

Family Polytrichaceae — Polytrichaceae

Genus Polytrichum — Polytrichum. The structure of true mosses and their life cycle with alternation of generations are exemplified by haircap moss—Polytrichum commune (Fig. 3.99).

Fig. 3.99. Life cycle diagram of haircap moss: 1 — male and female gametophytes; 2 — antheridium with spermatozoa; 3 — spermatozoon; 4 — archegonium with egg cell; 5 — Development of the Zygote from the fertilized egg cell; 6 — developing sporophyte; 7 — mature sporophytes on female gametophytes; a — seta; b — capsule; c — calyptra; d — operculum; e — columella; f — sporogenous Cells of the sporangium and spore formation therefrom (Meiosis); 8 — spores (+ and −); 9 — spore germination; 10 — male and female protonemata

Family Sphagnaceae — Sphagnaceae

Genus Sphagnum — Sphagnum (Fig. 3.100). Plants of this genus are commonly known as white or peat mosses due to their pale coloration and their ability to form a brown mass—peat—when the lower portions of their stems die off. Growing on acidic substrates, they form cushion-like mats. Their stems lack rhizoids, and lateral branches are arranged in whorls. Leaves are spirally imbricate, lacking veins, with water-storage cells at the base. The leaf blade (Fig. 3.100) is single-layered, consisting of Two Types of cells: some are narrow, green, and photosynthetic, while others are large, colorless, water-holding (hyaline) cells with thickened, porous walls. Antherodia on stalks are situated among the leaves of lateral branches, and archegonia are located at the apex of the shoots. Following fertilization, these develop into sporophytes (sporogonia) with a false, short stalk and a spherical capsule. The protonema is thalloid (plate-like), with rhizoids.

Fig. 3.100. Peat moss Sphagnum: A — general view of the gametophyte with sporogonia; Б — sporogonia; В — protonema; 1 — sporogonium stalk; 2 — sporogonium capsule; 3, 4, 5 — gametophyte leaves (general view, surface view under a Microscope, cross-section); 6 — archegonia; 7 — antheridia; a — photosynthetic cells; б — water-holding cells; в — pores

During the natural die-off and partial decomposition of mosses under conditions of excessive moisture and limited air access, peat and sapropel are formed. Peat is a combustible mineral resource representing a colloid of Cellulose, Lignin, resins, acids, and various organic and mineral compounds. It is used as a fertilizer, fuel, building material, and absorbent bedding for livestock. It serves as a raw material for producing industrial and montan Waxes, printing inks, oxalic, acetic, and humic acids, ethanol, furfural, cellulose, fodder Yeast, activated carbon, Pharmaceuticals, and more. Sapropel is a bottom organic silt comprising decomposed remains of PLANT AND ANIMAL organisms. It is rich in nitrogen, phosphorus, potassium, Trace Elements, and microorganisms that destroy pathogens of anthrax, paratyphoid, and brucellosis. Sapropel is utilized as animal feed, fertilizer, and a raw material for producing liquid fuels, coke, adhesives, ceramic pipes, pharmaceuticals, and other products.