BOTANY: Lecture Course for Bachelor Degree Students Specializing in «Agronomy» - 2016

LECTURE 6. Plant Reproduction. Vegetative Reproduction. Content and Objectives of Plant Taxonomy

METABOLISM/2.html">THE CONCEPT OF reproduction. Reproduction as one of the Fundamental properties of living organisms. Modes of plant reproduction. Practical significance of Vegetative Reproduction in agricultural practice. Asexual reproduction and its essence. Spore-forming Organs. Types of spores. Spores of Selection/8.html">Asexual and sexual reproduction. Sporogenesis in various taxonomic groups as Evidence of the unity of the plant world. Sexual reproduction. Gametes and zygote. Biological essence of Fertilization. Evolution of forms of sexual reproduction. Copulation, conjugation, somatogamy, gametangiogamy, zygogamy. Alternation of nuclear phases in The life cycle. Utilitarian, artificial, natural, and phylogenetic systems of the plant world. The concept of taxonomic units (taxa). Binomial nomenclature by C. Linnaeus. Species and infraspecific taxa. Modern formal Classification of organisms. The concept of higher and lower plants.

Acellular prokaryotic organisms. Viruses and Phages. General characteristics, Structure, and developmental cycles of viruses and phages. Classification of viruses. Viruses as causative agents of plant, animal, and human diseases. Prokaryotes. KINGDOM MONERA (Prokaryota). Division Bacteria. General characteristics. Structure, life-cycle features, and reproduction. Classification of Bacteria. Significance of bacteria. Division Cyanobacteria (Blue-green Algae). General characteristics. Structural features, lifestyle, and reproduction. Main representatives.

The reproduction of likeness, which ensures the survival of a species in space and time.

Reproduction of offspring is one of the fundamental properties of living organisms, alongside growth, Nutrition, etc. Without it, individuals leave no descendants, and the species goes extinct. The formation of offspring involves:

- reproduction (Replication) — the general property of organisms to produce offspring similar to themselves.

- procreation (multiplication) — the general property of organisms to produce offspring accompanied by an increase in the number of individuals of a given species.

The formation of offspring does not always lead to an increase in population size (the number of daughter individuals equals or is less than the number of parent individuals), wherein the replacement offspring practically do not coexist with the parents in time. Likewise, reproduction is frequently unaccompanied by replication (spores of the male shield fern germinate into prothallia that are unlike the sporproducing parent plant).

- Progressive species — rapidly reproducing, expanding their geographic range.

- Stable species — constancy in the number of individuals and range size.

- Regressive (endangered) species — shrinking number of individuals and territory of their range.

Modes of reproduction: vegetative, asexual, and sexual.

In the ontogeny of plants, reproduction can be single or recurring; accordingly, plants are referred to as monocyclic or polycyclic. The same Organism can reproduce both asexually and sexually.

Vegetative reproduction is the reproduction via PARTS OF THE thallus, organs or parts of plant organs, or primordia of daughter individuals (buds) capable of developing into an independent plant. The resulting progeny is referred to as a clone.

Unicellular plants (bacteria, blue-green algae, diatoms, certain green algae) — Cell Division.

Multicellular and large acellular organisms (algae, Fungi, Lichens) — fragmenting into parts, which is the least advanced method of vegetative reproduction.

In fungi — specialized unicellular adaptations for vegetative reproduction: conidia, oidia, and chlamydospores.

Forms of vegetative reproduction: blue-green algae reproduce by hormogonia; fungi by conidia, oidia, and chlamydospores; lichens by isidia and soredia containing several unicellular algae intertwined with fungal hyphae; and via vegetative organs through the division of the plant into parts, aboveground and underground shoots, leaves, and roots.

Natural vegetative reproduction occurs in nature without human intervention. Annual and biennial plants do not reproduce vegetatively.

The most widespread forms of vegetative reproduction in seed plants:

- via rhizomes (horsetail, couch grass, yarrow, bogbean, oregano, melissa, hellebore, valerian, lily of the valley).

- via bulbs — herbaceous plants — monocots from the families Liliaceae and Amaryllidaceae (onion, tulip, lily, autumn crocus, ramsons, saffron).

- via ROOT tubers — cyclamen.

- via root suckers — perennial sow thistle, yellow field sow thistle, dog rose, lilac, black locust, magnolia vine — shoots develop from adventitious buds formed on the roots. After the decay of the roots connecting the daughter plants to the maternal ones, the new plants become independent.

- via brood buds – small rudimentary shoots formed in leaf axils or inflorescences that, upon dropping from the parent plant, are capable of rooting (such as Bryophyllum and sundew), or modified into bulbs (as in bulbous bluegrass and lilies) or bulbils.

- via fragmentation – the splitting of an individual into two or more parts (such as stem segments), each capable of regenerating into a new organism (characteristic of filamentous and thalloid algae, as well as certain angiosperms like Canadian waterweed — where only female specimens were introduced to Europe — prickly pear cactus, and willow).

Artificial vegetative propagation

Carried out by humans, this method involves the surgical Separation of specific plant parts:

- when a plant fails to produce seeds (such as seedless varieties of mandarins and grapes),

- when seed propagation does not preserve desirable cultivar traits,

- to rapidly multiply a specific cultivar or plant;

- when cultivating peaches on apricot or almond rootstocks.

Methods:

1) Root suckers – raspberries, cherries, plums, blackberries, sea buckthorn, schisandra, black locust, aspen, etc.

2) Division of the bush – ornamental plants (primrose, daisies, delphinium, goldenrod), vegetables (sorrel, rhubarb), and medicinal herbs (valerian, echinacea, belladonna);

3) Layering – gooseberries, ficus, carnations, roses, oleander, azaleas, grapes;

4) Propagation by cuttings:

- stem cuttings (dormant and softwood), root cuttings, and leaf cuttings.

- Dormant stem cuttings – grapes, currants.

- Summer softwood cuttings – chrysanthemums, dahlias, cucumbers, eggplants.

- Root cuttings – horseradish, dog rose, roses.

- Leaf cuttings – begonias, gloxinias, purslane, coleus, hyacinths, tomatoes.

5) Grafting (transplantation) – the fusion of cut cuttings or buds

of one plant – the scion (to be propagated) – with another rooted plant – the rootstock.

I.V. Michurin developed the mentor method, based on the physiological Influence of the rootstock on the scion.

Advantages of vegetative propagation: it reliably preserves varietal traits without deviation; however, it can lead to decreased resistance, Aging of enzymatic systems, and a shortened overall lifespan of the plants.

Asexual reproduction

Occurs via specialized propagules produced by the organism – zoospores and spores (found in algae, fungi, and all spore-bearing plants excluding seed plants).

Types of spores: motile, flagellated zoospores lacking a rigid polysaccharide Cell wall – typical of lower aquatic plants.

Non-motile spores (aplanospores) lack locomotory organs, are passively dispersed, and are protected by a rigid wall. They occur in terrestrial lower plants and all higher spore-producing plants (possessing a double wall consisting of the intine and exine).

Spores are formed through mitosis (microspores) or Meiosis (meiospores). They develop inside specialized organs known as sporangia, whereas zoospores are produced in zoosporangia and function as endospores.

Spores include homosporous and heterosporous types (microspores and megaspores).

Features of asexual reproduction include high reproductive intensity; rapid dissemination of the species as a direct result of this high rate; and high progeny uniformity, faithfully replicating the traits and CHARACTERISTICS OF THE parent plant.

Sexual reproduction

Throughout the evolution of higher plants, spore reproduction proved not to be the most efficient strategy for species survival and dispersal during interspecific competition, largely due to its persistent dependency on Water.

Biological essence: the fusion of genetically diverse material, ensuring The Emergence of genetically varied offspring exhibiting traits from both maternal and paternal organisms → making descendants more viable and better adapted to fluctuating environmental conditions. Following a dormancy period, The Cell divides and gives rise to a new individual.

Types of sexual processes:

Gametogamy.

Forms: Isogamy, heterogamy, oogamy.

Agametogamy: hologamy, conjugation, zygogamy, gametangiogamy. The sexual process is absent in prokaryotes and certain eukaryotes.

Plant reproduction cycles.

Reproduction cycles without Morphology/12.html">ALTERNATION OF GENERATIONS occur in plants that reproduce exclusively via a single method—either asexual or sexual. In asexual reproduction, spores are formed via mitotic division → the resulting plants remain haploid (e.g., Deuteromycetes, Chlorella).

Sexual reproduction features a haplophasic cycle (where only the zygote is diploid, as in Chlamydomonas, Spirogyra, and Ulothrix) and a diplophasic cycle (where both the zygote and the vegetative plant body are diploid, and only the gametes are haploid, as in the brown alga Fucus).

Reproduction cycles involving the alternation of two generations and nuclear phases—the sporophyte (diploid nuclear phase) and the gametophyte (haploid nuclear phase)—characteristic of Higher Plants and certain green and brown algae.

Plant systematics is one of the oldest biological sciences. Modern classification systems for plants, animals, and fungi are strictly hierarchical.

Species   Bread wheat

Genus   Wheat

Family  Poaceae ceae

Order  Poales ales

Class   Monocotyledons psida

Division  Flowering plants  phyta

Subkingdom  Land plants bionta

Kingdom  Plants  Plantae

Superkingdom Eukaryotes Eucaryota

The highest taxon is the division, and the lowest is the species.

Species is a group of individual populations capable of interbreeding to produce fertile offspring that inhabit a specific territory (range), share A number of morphological and physiological traits, exhibit specific types of interactions with the abiotic and biotic environments, and are isolated from other such groups of individuals by reproductive incompatibility in natural conditions.

C. Linnaeus proposed binomial nomenclature.

The International Code of Botanical Nomenclature is based on the following principles:

1. Botanical nomenclature is independent of zoological nomenclature.

2. THE PRINCIPLE OF typification.

3. The principle of priority in publication.

4. The principle of uniqueness.

5. The principle of universality.

Plant systematics is a branch of botany that studies plants in their unity, establishes relationships and degrees of difference between them; its tasks include plant description, naming, classification, and grouping them based on affinity and historical development. There are two main types: floristic and phylogenetic systematics.

The organic world of our planet is diverse and divided into 7 kingdoms: Viruses, Procaryotae, Protozoa, Chromista, Fungi, Plantae, Animalia.

There are about 350,000 plant species on Earth, which are divided into lower (thallophytes) and higher (cormophytes) plants.

Kingdom VIRUSES (VIRA)

Division VIROPHYTA

Viruses are the smallest acellular life forms capable of invading living Cells and reproducing exclusively inside them. They possess their own genetic apparatus that encodes the synthesis of Viral Particles by utilizing the biosynthetic and energetic machinery of the host cell. They are Obligate Intracellular Parasites at the genetic level. Widespread in the biosphere, they infect living organisms across all groups.

Discovered in 1886 by the Ukrainian microbiologist M. Hamaliya in a calf sick with rangeland fever. In 1892, the Russian scientist D. Ivanovsky discovered plant viruses (tobacco mosaic). The term was proposed in 1899 by the Dutch botanist and microbiologist M. Beijerinck.

Forms: extracellular (viral particles or virions) and intracellular (the virus-host complex).

Simple viruses consist of a protein coat, a capsid, and a nucleic acid (DNA or RNA). Their shape can be rod-like, spherical, or cubic.

Complex viruses consist of a protein coat, a capsid, and a nucleic acid (DNA or RNA), and may also contain a lipoprotein membrane, CARBOHYDRATES, and Enzymes.

Bacteriophages are viruses that parasitize bacterial cells. Discovered in 1898 by the microbiologist and epidemiologist M.F. Hamaliya. They consist of a prismatic HEAD, a tail, a base plate, and filamentous structures. The internal content of the head is a single or double-stranded DNA or RNA molecule.

Penetration process:

1 - collision of the bacteriophage with the bacterial cell;

2 - the outer coat of the bacteriophage contracts, exposing part of the core located within the tail, which forcefully penetrates The cell wall of the bacterium;

3 - the nucleic acid is injected from the bacteriophage head through the channel and tail into the interior of the cell;

4 - the bacterial cell produces not its own Proteins, but new copies of DNA or RNA, causing the cell to gradually perish. 15-20 minutes after infection, the cell wall ruptures, releasing progeny consisting of several hundred new viral particles that go on to infect new cells.

Human diseases include Influenza, measles, rabies, poliomyelitis, hepatitis, smallpox, herpes, and AIDS; animal diseases include FOOT-and-Mouth disease and plague; plant diseases include leaf spotting and wrinkling, as well as fruit yellows.

KINGDOM MONERA

Unicellular or colonial prokaryotic organisms, comprising two divisions: Bacteria and Cyanobacteria (blue-green algae).

Division Bacteria (Bacteriophyta)

3,000 species of unicellular, colonial, or filamentous prokaryotic organisms. Discovered in 1675 by Antonie van Leeuwenhoek.

The founder of microbiology is Louis Pasteur.

They lack a true nucleus, Mitochondria, Endoplasmic reticulum, and Plastids. The cell wall consists of pectin and murein (chemically similar to the cell wall of cyanobacteria). Externally, it is covered with a layer of mucus or a tightly adhering capsule. The Cytoplasm is dense and contains Glycogen granules, proteins, and Lipids. Nucleic Acids are either diffusely distributed or concentrated in a nuclear region known as the nucleoid. Older cells contain vacuoles; green coloration is due to the pigment bacteriochlorophyll, while purple coloration is due to carotenoids.

Shape: coccoid; bacilli; vibrios; spiral (spirilla, coiled into 2–3 turns; spirochetes, coiled into multiple turns).

Capable of active movement (via flagella and rhythmic cell contractions). Flagellar arrangement: from one to many, located at one pole, both poles, or distributed over the entire surface. Flagella are simple fibrillar filaments composed of flagellin.

Reproduction:

- binary fission (amitosis);

- via spores: endospores and microcysts.

Under adverse conditions, they form a cyst. They can survive for many years at temperatures ranging from -180° C to +250° C.

Nutrition involves the absorption of nutrients through a semipermeable membrane.

According to their nutritional type, they are autotrophs and heterotrophs.

Respiration occurs across the entire cell surface via respiratory enzymes.

Based on their oxygen requirements, they are classified as aerobic and anaerobic.

Putrefaction is the process by which bacteria decompose nitrogenous compounds into ammonia and hydrogen sulfide.

Fermentation is the anaerobic breakdown of carbohydrate-containing compounds.

Types of fermentation:

- Lactic acid fermentation – milk sugar is broken down into lactic acid (used in fodder ensilage, and the fermentation of vegetables, fruits, and mushrooms);

- Butyric acid fermentation – under a neutral medium reaction, butyric and carbonic acids and hydrogen are formed; under an acidic reaction, acetone, butyl alcohol, carbon dioxide, and hydrogen are produced;

- pectin fermentation – facilitated by butyric acid bacteria, involving The breakdown of pectic substances that cement the bast fibers of flax and hemp;

- acetic acid oxidation – The oxidation of alcohol to acetic acid.

According to N. A. Krasilnikov's classification, they are divided into 4 classes:

- Class True Bacteria

Unicellular microorganisms of various shapes (bacilli, cocci, spirilla), capable of forming a capsule and actively moving via flagella; they reproduce by binary fission or motile gonidia.

- Class Actinomycetes

They form vegetative structures analogous to fungal hyphae. The mycelium of actinomycetes is capable of branching.

- Class Mycoplasmas

Of uncertain origin, these tiny cells lack cell walls and produce long extensions resembling actinomycete hyphae. Widespread in nature, among animals, in soils, and composts; they act as Saprophytes.

- Class Myxobacteria

The most advanced bacteria, possessing a well-defined nucleus and forming fruiting bodies. Rod-shaped or spherical cells reproducing by constriction. Movement is jet-propulsion-based. Saprophytes involved in the decomposition of plant residues.

- Class Spirochetes

Highly motile, possessing a flexible, wavy cell wall. Saprophytes and parasites (causative agents of Syphilis, relapsing fever, and infectious jaundice).

- Division Cyanobacteria (Cyanophyta)

2,000 species inhabiting water bodies, soils, and tree bark (with 500 species found in Ukraine). Unicellular, colonial, or, less commonly, multicellular prokaryotic organisms. Cells feature a rigid cell wall composed of Pectins, Amino Acids, Fatty acids, lipopolysaccharides, and murein. The wall is capable of mucilaginous transformation, forming mucous sheaths. The cytoplasm is enclosed by a Plasmalemma; a typical endoplasmic reticulum is absent, its Functions being performed by a developed membrane system that includes, alongside the plasmalemma, thylakoid membranes, mesosomes (mitochondrial analogs), and other membranous structures.

Photosynthetic products include Glycoproteins, Polysaccharides, and volutin.

- Class Chroococcales

Colonial, less frequently unicellular forms. Colonies range from simple to complex. Reproduction occurs via cell division in unicellular forms, and via colony fragmentation in colonial forms. They are responsible for water blooms.

- Class Chamaesiphonales

Epiphytic unicellular algae attached to a substrate. Reproduce via spores. Inhabit both fresh and saline water bodies.

- Class Hormogonales

Filamentous algae in which the protoplasts of adjacent cells are interconnected via plasmodesmata. They reproduce through hormogonia, and some species via spores. Spirulina is used in Human nutrition. Harmful species can cause fish kills and massive mortality among waterfowl and domestic animals.