Introduction to Botany

The fundamental aim of botany as a basic biological science is to elucidate the patterns of organization, functioning, reproduction, evolution, and distribution of plants at all levels of their organization — from molecular to biospheric (Raven et al., 2013; Mauseth, 2017). Achieving this aim provides an understanding of the place of plants in the overall system of living organisms and their role in maintaining biospheric processes.

The principal fundamental tasks of botany include:

Fundamental knowledge of plants constitutes the scientific basis for solving a wide range of applied problems, primarily in agronomy, breeding, nature conservation, and biotechnology (Bidlack & Jansky, 2021; Raven et al., 2013). Without understanding the fundamental patterns of plant structure and functioning, their effective cultivation, improvement of varietal qualities, and rational use of plant resources are impossible.

Alongside fundamental research, botany addresses a wide range of applied tasks aimed at meeting the practical needs of humanity. The importance of plants as sources of food, feed, medicines, fibers, timber, fuel, and other products determines the high demand for botanical knowledge in various sectors of the economy (Bidlack & Jansky, 2021; Graham et al., 2014).

The principal applied tasks of botany include:

Agronomic aspects of botany occupy a special place in the applied sphere. Agronomy as the science of agricultural production is based on fundamental botanical knowledge. The most important agronomic tasks of botany include:

Thus, applied botany, and especially its agronomic component, provides the scientific basis for sustainable plant production, conservation of genetic resources, and food independence of nations (Raven et al., 2013; Graham et al., 2014). Achievements in this field directly affect food security, public health, and economic welfare.

Plant systematics (from Gk. systematikos — ordered) is the branch of botany concerned with the description, identification, nomenclature, and classification of plants (Simpson, 2019). The aim of systematics is to construct a natural (phylogenetic) system of the plant world reflecting evolutionary relationships among taxa. The tasks of systematics include the inventory of species diversity, delimitation of species and infraspecific taxa, and study of evolutionary transformations (Yakovlev et al., 2006). Modern systematics employs data from morphology, anatomy, embryology, palynology, karyology, chemotaxonomy, and molecular phylogenetics (DNA sequence analysis) (Simpson, 2019; Mauseth, 2017).

Plant morphology (from Gk. morphē — form and logos — study) investigates the patterns of external plant structure, morphogenesis, and variation of organs in ontogeny and phylogeny (Serebryakova et al., 2006). The main branches of morphology include:

Plant anatomy (from Gk. anatemnō — to dissect) studies the internal structure of plants at the tissue and organ levels (Evert, 2006). The subject matter of anatomy is the structural organization of vegetative and reproductive organs, types of tissues, their cellular composition, and spatial arrangement. Anatomical studies are important for systematics (diagnostic characters), physiology (structure-function relationships), phylogeny (evolution of conducting and mechanical tissues), as well as for applied fields such as wood identification, pharmacognosy (microscopic analysis of medicinal raw materials), and forensic botany (Beck, 2010; Stern, 2021).

Plant cytology (from Gk. kytos — cell and logos — study) is the science of the plant cell: its structure, chemical composition, functions, and reproduction (Evert, 2006). The main areas include the study of cell wall structure and dynamics, membrane-bound organelles (plastids, mitochondria, vacuoles), the nucleus and chromosomes, and the processes of mitosis and meiosis. Modern cytology is closely connected with molecular biology and genetics (Mauseth, 2017; Stern, 2021).

Plant physiology (from Gk. physis — nature and logos — study) examines the vital processes of plants: photosynthesis, respiration, water relations, mineral nutrition, transport of substances, growth, development, and movement (Bidlack & Jansky, 2021; Strasburger, 1971). Plant physiology is one of the most experimental botanical disciplines, widely employing biochemical, biophysical, and molecular biological methods. The achievements of physiology constitute the scientific basis for crop production, agrochemistry, phytoremediation, and biotechnology (Raven et al., 2013; Graham et al., 2014).

Plant embryology (from Gk. embryon — embryo and logos — study) is the branch of botany that investigates the patterns of formation of male and female gametophytes, the processes of fertilization (including double fertilization in angiosperms), embryo and endosperm development, and seed formation (Lersten, 2004; Batygina, 2002). Embryological data are important for systematics, plant breeding (overcoming incompatibility, embryo culture), and seed science (Evert, 2006; Stern, 2021).

Plant geography (phytogeography) studies the patterns of plant distribution on Earth — the ranges of species and higher taxa, factors determining distribution boundaries, and the history of flora formation (Serebryakova et al., 2006; Mauseth, 2017). It includes floristic geography (study of individual species ranges and floristic complexes) and genetic geography (investigation of centers of origin of cultivated plants and their dispersal routes). Plant geography is closely related to climatology, geology, and paleobotany (Evert, 2006; Yakovlev et al., 2006).

Plant ecology (from Gk. oikos — dwelling, habitat) is the branch of botany that studies the relationships of plants with their environment (abiotic and biotic factors) and their adaptations to habitat conditions (Serebryakova et al., 2006; Mauseth, 2017). Within plant ecology, autecology (study of individual species) and synecology (study of plant communities) are distinguished. Ecological knowledge is essential for developing conservation measures, rational use of plant resources, and predicting the consequences of climate change (Raven et al., 2013; Graham et al., 2014).

Geobotany (phytocenology) is the science of vegetation cover — its structure, dynamics, and classification (Serebryakova et al., 2006). The subject matter of geobotany includes phytocenoses (plant communities), their composition, structure, productivity, successions, and spatial distribution. Geobotanical research provides the basis for vegetation mapping, assessment of forage lands, establishment of nature reserves, and forest management (Evert, 2006; Stern, 2021).

Paleobotany (from Gk. palaios — ancient and botanē — plant) studies fossil plants and the historical development of the plant world on Earth (Beck, 2010; Graham et al., 2014). The main methods include analysis of macrofossils (leaves, stems, fruits, seeds) and microfossils (spores, pollen — palynology, phytoliths). Paleobotany allows reconstruction of the phylogeny of taxa, determination of the time and place of origin of key adaptations (e.g., seeds, flowers, vascular tissues), and reconstruction of past climates and ecosystems (Simpson, 2019; Evert, 2006).

By object of study, the following specialized divisions are distinguished:

Applied botanical disciplines are oriented toward the practical use of plants and botanical knowledge:

Thus, the structure of botany reflects the diversity of approaches to studying the plant world — from the molecular-cellular level to the biogeocenotic and applied levels. Individual divisions mutually enrich each other, providing a holistic understanding of plants as complex biological systems (Evert, 2006; Serebryakova et al., 2006).

Light microscopy is the classical method for studying plant cells, tissues, and organs. Modern light microscopes (including phase-contrast, interference, and fluorescence microscopes) allow observation of living and fixed specimens at magnifications up to 1500× (Evert, 2006; Stern, 2021). Various stains and histochemical reactions are used to enhance contrast and selectively visualize structures (toluidine blue, safranin, phloroglucinol — for lignin; Sudan black — for suberin and cutin; PAS reaction — for polysaccharides) (Beck, 2010; Mauseth, 2017).

Electron microscopy is a method for ultrastructural analysis. Transmission electron microscopy (TEM) allows the study of the internal structure of cellular organelles, membranes, and cell walls at a resolution of 0.1–0.2 nm. Scanning electron microscopy (SEM) provides three-dimensional images of cell and tissue surfaces (Evert, 2006; Serebryakova et al., 2006). It requires complex fixation, dehydration, resin embedding, and ultramicrotomy.

Microtomy — preparation of thin (1–10 μm) and semi-thin (0.5–2 μm) sections for light and electron microscopy using rotary microtomes, ultramicrotomes, and vibratomes (Evert, 2006). Frozen sections are used for histochemistry and localization of soluble substances (Stern, 2021).

Morphological analysis methods — description of plant organs using standardized terminology, morphometric measurements (length, width, area, angles), construction of morphogenetic series, comparative-morphological and evolutionary-morphological approaches (Serebryakova et al., 2006; Mauseth, 2017).

Embryological methods — isolation and fixation of ovules and embryo sacs, preparation of serial sections, clearing of whole objects (Berlese method, Herr’s clearing fluid) to study gametophyte development, fertilization, and embryogenesis (Lersten, 2004; Batygina, 2002). Methods of isolated embryo culture and embryoculture are widely used (Stern, 2021).

Physiological methods — measurement of photosynthesis intensity (gas analysis, manometry, chlorophyll fluorescence), respiration (respirometry), transpiration (potometers, porometers), water potential (psychrometry, pressure chamber method), mineral composition (atomic absorption spectrometry) (Bidlack & Jansky, 2021; Raven et al., 2013). Hydroponic and aeroponic cultures are used to control mineral nutrition (Strasburger, 1971).

Biochemical methods — chromatography (paper, thin-layer, high-performance liquid chromatography — HPLC), electrophoresis (proteins, isozymes, nucleic acids), spectrophotometry (determination of pigments, enzymes, secondary metabolites), mass spectrometry (compound identification) (Graham et al., 2014; Stern, 2021).

Molecular phylogenetics — DNA sequencing (chloroplast, mitochondrial, nuclear) and construction of phylogenetic trees. Marker genes (e.g., rbcL, matK, ITS) are widely used in systematics and evolutionary biology (Simpson, 2019; Mauseth, 2017).

Genomic and post-genomic technologies — whole genome sequencing, transcriptomics (RNA-seq), proteomics, and metabolomics allow identification of genes controlling morphogenesis, adaptations, and the synthesis of useful compounds (Evert, 2006; Raven et al., 2013).

Cytogenetic methods — karyotype analysis (metaphase stages, differential chromosome staining, FISH — fluorescence in situ hybridization), chromosome counting, detection of polyploidy and aneuploidy (Lersten, 2004; Stern, 2021).

Field methods — establishment of sample plots, geobotanical description of phytocenoses, abundance assessment (visual, count-weight method), vegetation mapping (Serebryakova et al., 2006; Evert, 2006). Transect methods and permanent sample plots are used to study successions (Raven et al., 2013).

Quantitative methods — data processing using mathematical statistics (analysis of variance, correlation, regression analysis), species diversity indices (Shannon-Weaver index, Simpson index), cluster analysis and ordination (non-metric multidimensional scaling, DCA) for vegetation classification (Mauseth, 2017; Stern, 2021).

Physicochemical methods in ecology — measurement of light intensity, temperature, humidity, soil pH, elemental content, gas composition (Graham et al., 2014).

Macrofossils — study of leaf, stem, fruit, and seed imprints, fossil wood (anatomy of fossil plants, coal maceration methods) (Beck, 2010; Graham et al., 2014).

Microfossils — palynological analysis (study of spores and pollen using light and electron microscopy after chemical treatment of rock), phytolith analysis (siliceous structures in cells) (Evert, 2006; Simpson, 2019).

Tissue and organ culture — growing isolated meristems, calli, and protoplasts on nutrient media for plant regeneration, clonal micropropagation, and genetic transformation (Bidlack & Jansky, 2021; Stern, 2021).

Genetic engineering methods — transformation of plants using Agrobacterium tumefaciens, biolistics (gene gun), CRISPR/Cas9 genome editing, creation of transgenic plants (Raven et al., 2013; Graham et al., 2014).

Physiological experiments — modification of light conditions, temperature, water supply, mineral background, treatment with phytohormones and inhibitors to study regulation of growth and development (Bidlack & Jansky, 2021; Strasburger, 1971).

Herbarium techniques — collection, drying, mounting, and storage of reference plant specimens in herbaria (Simpson, 2019; Yakovlev et al., 2006). Herbarium collections are the basis for taxonomic, floristic, and areal studies.

Diagnostic methods — use of morphological, anatomical, embryological, palynological, chemotaxonomic characters to determine taxonomic affiliation (Mauseth, 2017; Evert, 2006).

Karyosystematics — study of the number, shape, and structure of chromosomes (karyotypes) to solve systematic questions (Lersten, 2004; Stern, 2021).

Growth and productivity models — mathematical models (e.g., production process models, biomass distribution, transpiration and photosynthesis models) that allow prediction of yield, plant growth, and environmental influences (Raven et al., 2013; Mauseth, 2017).

Evolutionary models — molecular clock methods, ancestral state reconstruction, range modeling (Evert, 2006; Simpson, 2019).

Thus, modern botany is a methodologically well-equipped science, employing a complex of complementary approaches — from classical descriptive to high-tech molecular and computational methods. The choice and combination of methods are determined by the objectives of the specific study and allow obtaining reliable and reproducible results (Evert, 2006; Serebryakova et al., 2006).

The origins of botanical knowledge are rooted in the practical needs of ancient people — the recognition of edible, medicinal, and poisonous plants. The first systematized information on plants is found in the works of the ancient Greek philosopher and naturalist Theophrastus (c. 370–285 BCE), a student of Aristotle. His works «Enquiry into Plants» and «On the Causes of Plants» laid the foundations of descriptive morphology, systematics, and plant ecology. Theophrastus is rightly called the "father of botany" (Serebryakova et al., 2006; Yakovlev et al., 2006).

In ancient Rome, botanical research developed primarily in an applied direction — in connection with medicine and agriculture. The works of Dioscorides (1st century CE) «De Materia Medica» and Pliny the Elder (1st century CE) «Natural History» summarized knowledge of several hundred plants and their uses.

In medieval Europe, botanical science declined; knowledge was preserved and accumulated mainly in monasteries. In the Arab East, botany and pharmacy flourished (works of Avicenna, 10th–11th centuries). With the Age of Great Geographical Discoveries (15th–16th centuries), a flood of previously unknown plants entered Europe, stimulating the development of descriptive botany, the creation of herbals ("travniki"), and the establishment of the first botanical gardens (Padua, 1545; Pisa, 1545) (Mauseth, 2017; Stern, 2021).

The outstanding German botanists of the 16th century — Otto Brunfels, Hieronymus Bock, Leonhart Fuchs — laid the foundations of scientific botanical terminology and illustrated plant systematics (Serebryakova et al., 2006).

The invention of the microscope (c. 1590) and its improvement opened new horizons. Robert Hooke (1665) first described the cellular structure of plants and introduced the term "cell." Marcello Malpighi and Nehemiah Grew (late 17th century) laid the foundations of plant anatomy (Evert, 2006; Beck, 2010).

Experimental plant physiology began with the experiments of Jan van Helmont (17th century) on plant nutrition and Joseph Priestley (18th century), who discovered the release of oxygen by plants during photosynthesis (Strasburger, 1971; Bidlack & Jansky, 2021).

The culmination of 18th-century systematics was the work of Carl Linnaeus (1707–1778). In Systema Naturae (1735) and Species Plantarum (1753), he introduced binomial nomenclature (genus and species name) and created an artificial classification of plants that became the basis for all botanical work for a century (Simpson, 2019; Yakovlev et al., 2006).

The 19th century was marked by the creation of the cell theory (M. Schleiden and T. Schwann, 1838–1839), proving that the cell is the universal structural unit of all organisms (Evert, 2006; Serebryakova et al., 2006).

Wilhelm Hofmeister (1850s) established the homology of alternation of generations in higher spore-bearing and seed plants, laying the foundations of evolutionary morphology and plant embryology (Lersten, 2004; Beck, 2010).

Charles Darwin’s theory of evolution, On the Origin of Species (1859), revolutionized botany, stimulating the development of phylogenetic systematics, evolutionary morphology, ecology, and plant geography (Mauseth, 2017; Graham et al., 2014).

Plant physiology achieved significant success through the work of Julius Sachs, Wilhelm Pfeffer, and other scientists who introduced precise experimental methods (water cultures, gas analysis) (Strasburger, 1971; Raven et al., 2013).

At the end of the 19th century, Sergey Gavrilovich Navashin (1898) discovered double fertilization in angiosperms — a phenomenon unique to flowering plants (Lersten, 2004; Batygina, 2002).

The 20th century witnessed the rapid development of plant genetics (rediscovery of Mendel’s laws in 1900, the work of N.I. Vavilov on centers of origin of cultivated plants and the law of homologous series), the introduction of electron microscopy, which made it possible to study the ultrastructure of cells (Evert, 2006; Mauseth, 2017).

The elucidation of the DNA structure by Watson and Crick (1953) opened the era of molecular biology. Molecular phylogenetics radically changed plant systematics, demonstrating the monophyly of many taxa and revising traditional classifications (Simpson, 2019; Graham et al., 2014).

In recent decades, genomics, transgenomics, genome editing (CRISPR/Cas9), bioinformatics, and plant systems biology have been actively developing. Plant biotechnology allows the creation of varieties with desired traits (resistance to herbicides, insects, drought; enhanced vitamin content) (Bidlack & Jansky, 2021; Raven et al., 2013).

In Russia, botanical research began with the study of the flora of Siberia and the Far East by expeditions of D.G. Messerschmidt, J.G. Gmelin, P.S. Pallas, S.P. Krasheninnikov (18th century). In 1714, by decree of Peter the Great, the "Apothecary Garden" (now the Komarov Botanical Institute of the Russian Academy of Sciences) was founded in St. Petersburg (Yakovlev et al., 2006; Serebryakova et al., 2006).

The most prominent Russian botanists of the 19th–20th centuries include: A.N. Beketov (founder of plant geography), V.L. Komarov (editor of the 30-volume Flora of the USSR), N.I. Vavilov (genetics and breeding, the doctrine of centers of origin of cultivated plants), V.N. Sukachev (founder of phytocenology and the theory of biogeocenosis), A.L. Takhtajan (creator of a new phylogenetic system of angiosperms), T.B. Batygina (plant embryology) (Serebryakova et al., 2006; Evert, 2006).

A detailed account of the history of botany, including a chronology of major discoveries and scientific schools, will be presented in a separate article.