BOTANY WITH BASICS OF HYDROBOTANY (AQUATIC PLANTS OF UKRAINE) - B.Ye. Yakubenko - 2011

VI. SYSTEM OF THE PLANT WORLD

Plants are unicellular, colonial, acellular, or multicellular, eukaryotic, phototrophic organisms.

The plant kingdom is divided into two subkingdoms: Lower Plants and Higher Plants.

LOWER SPORE PLANTS

GENERAL CHARACTERISTICS AND FEATURES

Algae are the primary components of phytohydrobionts in our Water bodies, determining their species diversity and phytoproductivity. Algae do not constitute a systematic taxon, but rather a biological or ecological group of organisms. The total number of currently known species exceeds 40,000, while their actual number is estimated to be 4 to 8 times—and according to some researchers, up to 250 times—greater. For instance, the number of species in just a single algal group, the diatoms, is believed by some authors to reach 10 million.

The algal diversity of Ukraine comprises about 5,000 species, represented by over 6,000 infraspecific taxa. Algae are ancient Representatives of the plant world, having emerged about 3.5 billion years ago. Thanks to stable living conditions in the aquatic environment, algae have reached us in an almost primitive state. They share the following common features: a) type of Nutrition (photoautotrophic—they contain Photosynthetic Pigments, meaning they feed primarily autotrophically); b) thallus (body) Structure—absence of differentiation into roots, stems, and leaves; c) structure of female sex Organs—unicellular (with the exception of Charophyceae).

From an ecological perspective, these are organisms whose existence is largely tied to water (as indicated by their very name) — either throughout their entire life cycle or solely during the reproduction period, particularly in forms living on or in the soil (soil algae), in the aerial environment, or among the epilithic/epiphytic growths of various structures. However, all these are secondary communities, because the reproduction of the algae within them still takes place in water.

Thus, algae are a collective group of lower thallophytic plants uniting organisms that lack a clear differentiation into roots, stems, and leaves, reproduce via spores, and are characterized by an autotrophic type of nutrition; that is, as a rule, they are chlorophyll-bearing plants containing the green pigment chlorophyll and other photosynthetic pigments in their Cells, and they live predominantly in water.

Algae are unicellular, colonial, less frequently multicellular, and only occasionally acellular (lacking Cell walls) organisms represented by prokaryotic and eukaryotic forms. Their sizes range from a few micrometers to tens, and sometimes hundreds, of meters.

Prokaryotic algae (cyanoprokaryotes — blue-green algae) lack a well-defined nucleus (no nuclear envelope), Endoplasmic reticulum, Golgi bodies, microtubules, membrane-bound Organelles such as Mitochondria and Plastids, complexes of DNA with Nuclear Proteins in Chromosomes, mitosis, and a true sexual process.

The Cell of eukaryotic algae is similar in structure to that of higher plants, possessing all the standard components, but exhibits certain specific features in its Organization (such as the variety of chloroplast types and structures, cell walls, and outer cellular membranes and coats). The presence of various pigments causes the diverse coloration of algae, resulting in a rich spectrum of hues (green, blue-green, yellow-green, red, brown, etc.).

The Emergence of diverse photosynthetic pigments in algae was a major event in plant evolution, enabling these organisms to develop and thrive under a wide range of environmental conditions. The primary pigment in algae is chlorophyll *a*, although Other forms of chlorophyll—*b*, *c*, *d*—as well as various accessory pigments such as carotenoids and phycobilins, are found in certain groups. The combination of different pigments enables Photosynthesis under diverse ecological conditions, particularly at varying depths and water turbidities. Thus, in terms of nutrition, algae are predominantly autotrophs, though they can also feed heterotrophically by utilizing CARBOHYDRATES as a carbon source in the dark. In addition to carbon, some algae are capable of assimilating nitrogen not only from mineral compounds (nitrates) but also from organic sources such as amines and Amino Acids, and occasionally even directly from the air (in blue-green algae). Exceptionally, some algae exhibit holozoic (animal-like), saprophytic, or even parasitic modes of nutrition, though these are secondary traits manifested alongside their primary mode.

Algae are characterized by both sexual and asexual reproduction, which differ fundamentally both in the organization of specific forms and from an evolutionary standpoint. Specifically, asexual reproduction leads to the propagation of already existing life forms, whereas sexual reproduction is a process based on Gene recombination, resulting in the creation of new forms. Asexual reproduction is subdivided into: 1) Vegetative Reproduction — via vegetative cells or the vegetative division of the thallus (division of unicellular algae in half, thallus fragments — akinetes, hormogonia, gonidia, planococci, gemmae); 2) asexual reproduction proper, which occurs via specialized cells differing from vegetative ones and formed inside the mother cell — zoospores, autospores, exospores, and endospores.

All forms of the sexual process are known to occur in algae:

a) without gamete formation — hologamy ("holos" – whole, "gamos" – marriage [Greek]), the fusion of two cells that do not differ from vegetative cells. It is characteristic of primitive algae lacking a Cell wall, such as *Dunaliella* Teod. (green algae) and *Dinobryon* Ehrenb. (golden algae).

Conjugation — found in green (Zygnematales) and diatoms — involves the fusion of only two protoplasts, while The cell wall is not involved in forming the new individual;

b) with gamete formation (gametogamy or merogamy) — isogamy (copulation of two morphologically similar Gametes), heterogamy (copulation of two gametes differing in shape, size, and motility), oogamy (copulation of two gametes differing in size, where one is immobile: female gametes are large and non-motile, while male gametes are small and motile — characteristic of green and red algae, for example). The sexual process typically occurs under unfavorable environmental conditions.

Depending on whether algae reproduce sexually or not, Two Types of developmental cycles are distinguished:

1) if the sexual process is absent (*Chlorella* Beijer.), there is no alternation of nuclear phases; 2) if the alga reproduces sexually, the developmental cycle comprises two phases — diploid (2n) and haploid (n).

Three types of phase alternation (diploid/asexual and haploid/sexual) are known in algae: - Haploid type: the vegetative body is always haploid, and only the zygote is diploid (*Chlamydomonas* Ehrenb., *Spirogyra* Link). Reduction division (Meiosis) occurs during the germination of the zygote; - Diploid type: the vegetative body is always diploid. As a result of meiosis in the maternal diploid Organism, haploid gametes are formed; following Fertilization, a new maternal individual grows directly from the diploid zygote (without a resting period), and gametes are formed on it once again. Reduction division occurs within the gametangia. This type of development is typical, for example, of green siphonaceous algae of the genera *Caulerpa* Lamouroux and *Codium* Stackh.; - Diplo-haplophasic type: a diploid sporophyte (where organs of asexual reproduction are formed — the asexual generation) and a haploid gametophyte (the sexual generation). Haploid gametes are formed on the gametophyte via mitosis, followed by fertilization, and a sporophyte develops from the diploid zygote. Haploid spores are formed on the sporophyte through meiosis, which in turn give rise to gametophytes. This type of development is characteristic of brown algae, notably sugar kelp (*Laminaria saccharina* (L.) Lamouroux).

Algae exhibit two types of life-phase alternation (Morphology/12.html">ALTERNATION OF GENERATIONS): a) isomorphic type: the gametophyte is morphologically indistinguishable from the sporophyte (*Volvox* L., *Cladophora* Kutz., *Ulva L.*, *Oedogoniales*, *Charales*, *Dictyota*); b) heteromorphic type: the sporophyte is large, whereas the gametophyte is microscopic — as seen in the brown alga sugar kelp and in green siphonaceous algae.

According to the traditional plant Classification system, algae belong to lower spore plants and unite organisms at various levels of evolutionary development and morphological body differentiation, represented by the following structural types: monad (flagellate) — motile unicellular and colonial organisms possessing active flagella; amoeboid (rhizopodial) — exclusively unicellular organisms lacking a rigid cell wall, possessing only a cytoplasmic membrane and capable of active movement via cytoplasmic projections (rhizopodia); palmelloid (capsal) — non-motile organisms whose cells are embedded in a common mucilage matrix without direct intercell connections, retaining an eyespot and contractile vacuoles (often retaining non-motile or sluggish flagella as well) and capable of dividing in various directions; coccoid — non-motile unicellular and colonial organisms with a rigid cell wall, lacking flagella and the ability for active movement; sarcinoid — a specialized Modification of the coccoid structure where Cell Division occurs in multiple planes through so-called vegetative cell division, leading to The formation of packet-like multicellular clusters; filamentous — thread-like arrangement of non-motile cells dividing predominantly in one plane with the formation of transverse septa via vegetative cell division; heterotrichous — a complex filamentous structure featuring two systems of threads: a horizontal system creeping along the substrate, and a vertical system rising upright from the first; parenchymatous (blad-like/sheet-like) — a multicellular thallus forming a blade consisting of one, two, or many cell layers, with divisions occurring not only transversely but also longitudinally; siphonaceous (acellular) — the absence of transverse cell walls in a thallus that contains A large number of organelles; siphonecphalous/siphonocladous — a complex siphonaceous structure resulting in the formation of a secondarily partitioned, multinucleate complex thallus.

Algae grow in A wide variety of biotopes and environments: they develop in water, forming the hydrophyton. As plant organisms, they constitute phytoplankton — the plant community inhabiting the water Column. In saline marine waters, the dominants are diatoms and an immense diversity of dinoflagellates, whereas in freshwaters, the core of the plankton is formed by green algae,

blue-green and yellow-green algae. Phytobenthos consists of algae developing near or on the bottom (brown, red, green, etc.). Periphyton comprises algae living on solid substrates among fouling communities and on water-immersed objects that are not a food source (diatoms, green algae, blue-green algae, etc.). Neuston is found in the surface water film (green, golden, and euglenoid algae). Edaphon includes algae living in or on the soil surface from 0.2-3 cm up to 1.5 m deep (green, yellow-green, and blue-green algae). Aerophyton lives in the air, on the trunks of trees and shrubs, on stones, rocks, etc. (the so-called aerophilic species, including green and blue-green algae).

Algae inhabit both normal environments and hot springs at temperatures ranging from -52 °С to +84 °С, as well as snow and ice (blue-green, diatom, and some green algae).

Algae form symbiotic associations with other organisms, including Bacteria, unicellular and Multicellular animals (the blue-green alga Socolovia develops on the legs of water mites, and Prochloron On the surface or inside of ascidians; the green alga Chlorangiopsis on the bodies of oligochaetes, rotifers, and protozoan "stalks", while Chlorella inhabits sponge cavities); Fungi (the blue-green alga Nostoc, and green algae such as Chlorella, Chlorococcum, Trebouxia, Myrmecia, Trentepohlia, and Cladophora in the thalli of Lichens); mosses (the yellow-green alga Myxochloris in the hyaline cells of Sphagnum, and the green alga Porochloris on the leaves of Sphagnum and Drepanocladus); ferns (the blue-green alga

Anabaena develops within the cavities of the water fern Azolla); gymnosperms and angiosperms (the green alga Chlorochytrium in the intercellular spaces of the subepidermal parenchyma of duckweed).

To understand these organisms and study their characteristics, various Methods of phycological research are employed: floristic and systematic (floristic-systematic), which is a long-standing and traditional approach combining The Study of algal diversity, taxonomic affiliation, and systematic hierarchy; morphological, involving the description of external appearance, shape, coloration, etc.;

ontogenetic, investigating the life history of an organism throughout its life cycle; cytological, examining intracellular structures using specific stains and fixatives via light and Electron Microscopy; ecological, studying organismal requirements in relation to environmental conditions through a) descriptive field observations and b) experimental Laboratory studies; physiological, analyzing physiological processes occurring within living organisms; molecular-genetic, exploring heredity, Variability, and the molecular structure of living organisms.

Understanding algae is impossible without grouping and systematizing them based on specific diagnostic features. However, algal Taxonomy is currently in a state of flux. Classification schemes at the level of higher taxa (division, Class) are numerous and often contradictory. Recently, electron microscopic, physiological-biochemical, and molecular-biological studies have yielded new data that do not always align with classical morphological-physiological criteria for taxon differentiation. Nevertheless, the types of photosynthetic Pigments and Their combinations (complexes), along with morphological-reproductive, ultrastructural, and certain molecular-Biological features of typical representatives, form The basis of the current algal classification into divisions. In the modern System of the living world, algae are distributed across 16 divisions belonging to two superkingdoms:

I. Superkingdom - Procaryota

Division Blue-green algae - Cyanophyta (Cyanoprocaryota)

II. Superkingdom - Eucaryota

Division Euglenophytes - Euglenophyta

Division Chlorarachniophytes - Chlorarachniophyta

Division Raphidophytes - Raphidophyta

Division Golden algae - Chrysophyta

Division Eustigmatophytes - Eustigmatophyta

Division Yellow-green algae - Xanthophyta

Division Brown Algae - Phaeophyta

Division Diatoms - Bacillariophyta

Division Dictyochophytes - Dictyochophyta

Division Dinoflagellates - Dinophyta

Division Haptophytes - Haptophyta

Division Cryptophytes - Cryptophyta

Division Glaucophytes - Glaucocystophyta

Division Red Algae - Rhodophyta

Division Green Algae - Chlorophyta

Algae play a vital role in nature and human life. As primary phototrophic organisms, they enrich the atmosphere and water with oxygen; they are used in wastewater Treatment and directly participate in the decomposition of Organic compounds. In conjunction with other organisms (such as bacteria and invertebrates), algae serve as indicator species in biological water analysis and take part in self-purification processes in aquatic ecosystems. Certain species are used as indicators of organic water pollution. Algae help determine the age of sedimentary rocks and facilitate the Formation of primary humus by colonizing barren substrates. In legal practice, they serve as an auxiliary tool in determining the cause of human death. They also provide industrial raw Materials—marine forms are used to produce iodine, bromine, Agar-agar, etc., while filamentous freshwater algae are utilized for chemical compounds (such as alcohols, ethers, and organic acids), as well as a source of Vitamins (e.g., Spirulina), Antibiotics, and growth stimulants. Macrophytes and unicellular forms are consumed as human food on Earth and in closed ecosystems during space missions (alongside oxygen production). In agriculture, they are used as livestock feed and applied directly to the soil (marine algae, certain freshwater green and blue-green filamentous algae, charophytes, and algal biomass responsible for water "blooms"). Nitrogen-fixing blue-green algae are specially cultivated and applied to soils in countries like Japan, China, and Uzbekistan, where they fix atmospheric nitrogen, accumulate organic matter, prevent mineral fertilizers from leaching out with rainwater or irrigation, and positively influence soil physical properties. Research is also underway to integrate algae into agrotechnical practices that promote intensive plant growth, as well as to extract rare elements, such as gold and silver, from ores industrially.

Blue-green and red algae, together with corals, have historically built and continue to build underwater reefs. Ancient reefs are associated with bauxite deposits in the Eastern Sayan Mountains and near the eastern slopes of the Urals (Russia), as well as significant oil deposits in Iran, Russia (Bashkortostan), and Ukraine (the Pre-Carpathians). A well-known example is Medobory—a forested ridge of high hills (up to 70 m) stretching from the city of Brody to Kamianets-Podilskyi, flanked on both sides by rocky formations known as Tovtry. These constitute an ancient barrier reef built primarily by red Algae in the coastal zone of a warm sea during the latter half of the Tertiary period.

Charophyte algae are important for improving the hydrological regime of water bodies and creating a distinct biocenosis that Supports abundant epiphytic algae, bacteria, and insect larvae, which serve as excellent fish feed. At the same time, it has been observed that mosquito larvae are absent or poorly developed in water bodies with dense growths of charophytes. Furthermore, the oospores of charophyte algae provide food for migratory birds, particularly ducks.

However, algae can also have a negative impact. Notably, they cause water "blooms," trigger toxicosis, and lead to fish mortality or the die-off of zooplankton due to algal metabolites and the consumption of contaminated water. They are also implicated in the biological corrosion of metals and the degradation of various materials, particularly in humid tropical climates.