PLANT PHYSIOLOGY AND BIOCHEMISTRY

Lecture Notes

1. SUBJECT AND TASKS OF PLANT PHYSIOLOGY. MAIN TRENDS IN MODERN PHYTOPHYSIOLOGY

Modern phytophysiology is an integrative discipline that examines the functional activity of plant organisms across various Levels of biological Organization.

Plant physiology is the science concerned with the functional activity of plant organisms.

The object of study in phytophysiology is the plant Organism at its various Levels of organization. The unique Specificity of its chemical composition, morphological Structure, and Functions, the dependence of metabolic processes on structural states, and the dynamic nature of these structures are the defining CHARACTERISTICS OF THE Subject Matter of this science.

The subject of plant physiology is The Study of the functions of living plant organisms, their Organs, Tissues, Cells, and cellular components.

The goal is to understand the principles of life processes and plant functions, uncover their underlying mechanisms, develop a conceptual framework for the Structural and functional organization of plant systems at different levels, and establish Methods for regulating plant organisms.

The problems and tasks of phytophysiology are so vast and complex that their resolution requires a comprehensive array of sophisticated Physicochemical methods, as well as diverse experimental and theoretical approaches. This is precisely why this discipline is ranked among the exact fundamental sciences.

Plant physiology undoubtedly holds a prominent place within the biological sciences. As part of the botanical cycle, it maintains close ties with biochemistry, biophysics, immunology, genetics, and mathematical modeling, with its closest link being to animal physiology.

The methodology of plant physiology is based on METABOLISM/2.html">THE CONCEPT OF the plant organism as a complex, self-regulating system encompassing a hierarchy of structural levels—from subcellular components to the entire plant. Understanding physiological functions is achieved by investigating simpler levels of organization, followed by the integration of data when examining physiological systems of increasing complexity.

To understand plant life, one must first analyze all individual manifestations of its vital activity; this is The Role of the analytical research method. Reconstructing the functional picture of the plant organism as a unified whole is achieved through the application of the synthetic method. Alongside these, phytophysiology widely employs field and Laboratory studies, observation and modeling, as well as various physicochemical, mathematical, experimental, and theoretical approaches.

The Implementation of these methods has led to The Emergence of general physiology, the physiology of specific crops, and applied physiology. The study of functional adaptations in ontogeny and phylogeny has given rise to evolutionary physiology.

At The current stage, it can be said that phytophysiology studies the transformation of matter, energy, form, and information within plants.

An important aspect of plant physiology is the practical orientation of its research, which is why this science is justifiably considered the theoretical foundation for rational crop production and modern biotechnologies. Advances in Introduction/32.html">Genetic Engineering METHODS are opening new possibilities for designing plants with novel, practically valuable properties.

Currently, the primary focus is on uncovering the mechanisms of self-regulation and integration that ensure the integrity of the plant organism, its resistance to environmental conditions, and high final productivity. This is primarily linked to the rising costs of producing a unit of plant output. A further doubling of crop yields requires a 20-30-fold increase in resource and Energy Expenditure. Plant physiology is now faced with The Challenge of creating resource-efficient plant organisms, including through the Genetic Transformation of photosynthetic and immune systems, as well as Nitrogen Fixation mechanisms.

The intensification of crop production and The Development of Ukraine's agricultural sector are becoming leading factors in the negative impact on the biosphere, causing chemical and biogenic pollution, including genetic contamination of the environment. Therefore, based on the study of plant physiology and biochemistry, it is necessary to find environmentally safe systems and technologies, such as new generations of plant growth regulators, fertilizers, and anti-stress agents, and to learn how to manage endogenous regulatory systems in plants, avoiding The Use of external (exogenous) chemical regulators.

Modern yield increases are accompanied by a decline in quality (reduced protein content in wheat, lower sugar content in sugar beets, and increased contamination of crop products with pesticides and herbicides). Therefore, it is necessary to develop the physiological foundations for managing crop quality by optimizing and balancing the processes of ROOT Nutrition and growth, Photosynthesis, and the accumulation of economically valuable products, including secondary metabolites.

A promising area remains the Study of the phototrophic function of plant organisms as the basis for the primary transformation of solar energy and the maintenance of ecological balance in the biosphere. Unlike plants, humans have not learned to directly utilize solar energy. The solution to this problem by the plant organism is on a level above any technical solutions currently known to humanity. The process of photosynthesis, inherent to plants, continues to hold the secret of how solar energy in green leaves creates food for all life on Earth. Uncovering The Nature of photosynthesis will bring us closer to understanding THE ORIGIN OF life, the efficient use of solar energy, the artificial synthesis of CARBOHYDRATES, fats, and Proteins, and the resolution of the energy crisis.

At a time when natural ecosystems are being catastrophically destroyed by anthropogenic stress, eco-physiological research, including that of wild plants, is gaining significant theoretical and practical importance.

Studying the human-beneficial properties of specific wild species (high resilience, competitiveness, types of life strategies) can point to ways of introducing these traits into the genotypes of cultivated plants. It can also help in selecting species for environmental restoration, phytoremediation, and ecological bioindication. Research in this direction will, in the future, allow for the Introduction of new species as sources of food and diverse raw Materials.

The physiology of diseased plants, the physiology of pathogenic Fungi, and The problem of plant-to-plant interactions (allelopathy), including their factors and mechanisms, require in-depth study.

Thus, plant physiology faces many interesting and important tasks. In a generalized form, these are:

1. Studying the principles of plant vital activity (mechanisms of nutrition, growth, reproduction, Water exchange, etc.), and investigating the functions of various plant parts during GROWTH AND DEVELOPMENT, which encompasses the emergence of specific functions and their transformation from one form to another.

2. Developing the theoretical foundations for achieving maximum crop yields (establishing optimal conditions for Plant Growth and Development and the possibilities for regulating these processes to maximize the provision of human needs for food, industrial raw materials, and livestock feed with desired characteristics and quality).

3. Investigating and clarifying the nature of Plant resistance to abiotic and biotic environmental factors, particularly in regions facing complex ecological challenges.

4. Studying the MECHANISMS OF NITROGEN fixation and photosynthesis to develop equipment for replicating these processes under artificial conditions.

History of the Development of Plant Physiology

I. The Current state of plant physiology is the result of a long developmental journey spanning over 250 years. It originated in the 17th and 18th centuries within the field of botany. The scientific approach to plant physiology began with the work of Jan Baptist van Helmont (1579–1644), who conducted the first quantitative vegetation experiment to study plant nutrition. Later, the classic works of Italian biologist Marcello Malpighi, "Anatomy of Plants" (1679), and English botanist Stephen Hales, "Vegetable Staticks" (1727), provided not only descriptions of plant structure but also the results of numerous physiological experiments.

Between 1772 and 1792, Joseph Priestley, Jan Ingenhousz, and Jean Senebier, building upon each other's work, identified the components responsible for plant aerial nutrition. Through precise chemical analysis, the Swiss scientist Nicolas-Théodore de Saussure proved that plants assimilate carbon from CO₂ in the presence of light. Thus, The phenomenon of photosynthesis was discovered, although the term "photosynthesis" was not proposed by Wilhelm Pfeffer until 1877.

The year 1800 was a landmark for plant physiology, as Jean Senebier published a five-volume treatise on the subject. It was the first textbook in the discipline to define its scope, methods, and objectives; it was also here that Senebier introduced the term "plant physiology."

II. The first Russian-language textbook on plant physiology was written by Prof. A. Famintsyn in 1887, and in 1891, the textbook by Ukrainian scientist V. Palladin was published, which subsequently went through nine editions.

In the 19th century, thanks to the efforts of scientists from various countries, the main branches of modern plant physiology were fully established:

- photosynthesis (J.B. Boussingault, J. Sachs, K.A. Timiryazev, M.S. Tswett, L. Marchlewski, A.N. Bakh);

- Respiration (A.S. Famintsyn, L. Pasteur, A.N. Bakh, G. Bertrand);

- water relations (G. Dutrochet, H. de Vries, J. Sachs);

- soil nutrition (J. von Liebig, J.B. Boussingault, W. Knop, M. Beijerinck, S.N. Winogradsky, D.N. Pryanishnikov);

- solute transport (W. Pfeffer, E.P. Votchal);

- growth and development (J. Sachs, A.S. Famintsyn, I.V. Baranetsky, A.F. Batalin, M.F. Levakovsky, G. Klebs);

- movement (T. Knight, C. Darwin, W. Pfeffer);

- irritability (J.S. Burdon-Sanderson, M.F. Levakovsky);

- plant resistance (D.I. Ivanovsky, K.A. Timiryazev).

III. The first half of the 20th century was characterized by the rapid and comprehensive development of plant physiology. The primary focus shifted to the biochemistry of respiratory mechanisms (V.I. Palladin, S.P. Kostychev, O. Warburg, D. Keilin, H. Krebs) and photosynthesis (R. Willstätter, C.B. van Niel, R. Hill, M. Calvin, D. Arnon).

Simultaneously, plant enzymology, experimental Morphology, and ecological plant physiology evolved. Virology, microbiology, biochemistry, and agricultural chemistry emerged as independent disciplines.

A major achievement was the discovery of endogenous growth and development regulators—phytohormones (N. Kholodny, D. Nelyubov, F. Went, F. Kögl, E. Kurosawa, T. Yabuta). Research into mineral nutrition continued (D. Sabinin, P. Vlasyuk), and theoretical foundations for plant resistance were established (N. Maksimov, I. Tumanov, P. Genkel).

In the second half of the 20th century, plant physiology trended toward a synthesis of biochemistry and molecular biology, biophysics and biological modeling, and Cytology and plant genetics. It became increasingly evident that life phenomena could not be understood within the confines of a single biological science. Physiology entered an era of synthesis. Consequently, interest grew in studying regulatory systems and the mechanisms ensuring the integrity of the plant organism (A. Kursanov, M. Chailakhyan, D. Grodzinsky). Research accelerated into the Mechanisms of Genetic information expression, the role of membranes in regulatory systems, and the modes of action of phytohormones.

All of this was facilitated by rapid progress in developing organ, tissue, and Cell culture methods, which also hold great practical significance (K. Sytnik, Y. Gleba, F. Kalinin).

Biotechnology, a new industrial sector, offers significant Prospects for plant physiology and biochemistry. In intensive agriculture, theories of mineral nutrition and water exchange, chemical growth regulators, herbicides, and fungicides are now widely applied.

The work of B. Keller and his students, dedicated to the problems of ecological physiology and plant Salt Tolerance, has gained great importance.