Plant Physiology - Lecture Notes - O. M. Tarnopilska 2019

1. Fundamentals of Plant Physiology
1.1 Concept of Plant Physiology and Its Connection with Other Sciences

Plant physiology (from the Greek physis – nature, and logos – study) is the science that investigates the vital processes and Functions of the plant Organism.

Modern plant physiology is an interdisciplinary, integrative science exploring the functional activity of plant organisms and the mechanisms of plant systems across various Levels of Organization—from the intact plant to its individual parts. Transformation, METABOLISM, substance transport between individual Organs and between the organism as a whole and its environment, assimilation and excretion, Respiration, GROWTH AND DEVELOPMENT, Functional and Structural differentiation, and reproduction—each of these functions, logically coordinated with the others, drives the individual Development of the organism, causing specific changes and altering the correlative integrity of the organism at each stage of ontogeny. All of this influences the further development of the integral system, which is self-organizing, self-regulating, and characterized by the deep interconnectedness of all its processes and phenomena.

Plant organisms are characterized by aerial, photosynthetic, and ROOT mineral Nutrition functions that are closely intertwined.

A specific feature of plant organisms is their autotrophy. The foundation of life for living organisms is a continuous exchange of matter and energy with the environment. However, only green plants and certain microorganisms are capable of using inorganic substances as raw Materials to synthesize vital Organic compounds. This specific property is called autotrophy, and the organisms themselves are referred to as autotrophs, in contrast to heterotrophs, which incorporate organic compounds synthesized by autotrophs into their metabolism. Furthermore, plants are autotrophic not only with respect to carbon, which they absorb as CO₂ and convert into organic matter through Photosynthesis, but also regarding other mineral elements such as nitrogen, phosphorus, and sulfur. Through a complex sequence of biochemical reactions and molecular-biological changes, combining the products of photosynthesis with metabolic products in the roots, stem, and shoots, light energy is expended to meet the needs of the entire plant, ensure the normal development of its organs, and acquire the elements from the soil required for the functioning of the whole organism.

Another key characteristic of plants is their relative immobility. Consequently, they respond purposefully to changing environmental conditions through their growth. Plants develop a substantial leaf surface area for more efficient absorption of CO₂ and sunlight, alongside an extensive root system to absorb Water and mineral salts. Hence, growth and the de novo formation of structures often form The basis of their functioning. In this regard, The transport of water and substances within the plant—both intercellularly (via membrane continuity and plasmodesmata) and through conducting vessels between specific organs—assumes great significance. Transport systems integrate organs and Tissues into a unified organism, playing a crucial role in regulating Plant Growth and developmental functions. Metabolic Specificity within individual organs and substance exchange establish the foundation for inter-organ interaction, thereby ensuring the integrity of the plant organism. Growth serves as the basis for The formation of all functions, and each function, in turn, undergoes specific changes throughout the plant's ontogeny.

One of the essential Functional Properties of plants is their ability to adapt to changing environmental conditions, which ensures Plant resistance to biotic and abiotic stresses.

Plant physiology studies the transformation of matter, energy, and form in plants, as well as information Processing. After all, all the traits and potentials of a plant that form during growth and development are materialized by the genetic apparatus solely through the assimilation of matter, energy, and information received from the environment. The environment itself acts as a factor that facilitates the Introduction/27.html">Translation of the genome's potential into specific plant traits. The spatial and temporal ordering of a vast array of potential reactions constitutes the foundation of the plant's capacity for self-regulation, self-preservation, and self-reproduction. Herein lies the dialectical unity between the information contained within the cellular genome and that received from the outside.

When studying plant life across all levels of organization (molecular, subcellular, cellular, tissue, organ, organismal, species, population, and biocenotic), one must bear in mind that plant physiology is grounded in the dialectical unity and interconnection of Structure and function. Thus, the understanding of physiological functions is achieved by investigating simpler levels of organization, followed by the integration of data when examining physiological systems of increasing complexity.

Living systems, and plant organisms in particular, exhibit a higher form of integrity, characterized by an inextricable link and mutual interdependence of their constituent parts. One manifestation of this integrity is that, despite the great importance of each individual function, the vital activity of the organism as a whole depends on how these interrelations shift in response to environmental conditions.

The integrity of the organism is driven by evolutionarily established interconnections among biochemical processes occurring within a specific organism. Clearly, uncovering the deep-seated mechanisms and The Essence of functions inherent to individual organs and the whole organism requires deepening scientific research at the molecular, genetic, and subcellular levels. In the near future, this will be facilitated by The ability to identify genes and decode the genomes of every specific plant species. Nevertheless, a vital role in revealing The Essence and content of the primary life functions of the intact plant organism belongs to plant physiology as a discipline that integrates the most advanced achievements of biochemistry, genetics, and molecular biology.

Establishing The Nature of correlative bonds and the physiological-BIOCHEMICAL FOUNDATIONS OF integrity is only possible by understanding the full complexity of plant organ growth and development processes, driven by metabolic diversity, which manifests through the interdependence and coordination of numerous individual reactions. Therefore, alongside concepts such as "structure," "function," "organ," "Cell," "organelle," and "molecule," modern plant physiology incorporates concepts such as "system," "integrity," "organization," "information," and "modeling."

Plant physiology undoubtedly holds a prominent place within The system of biological knowledge. Over recent decades, physiologists have successfully integrated Methods from biophysics, Cytology, and molecular biology. At the same time, they have preserved their integrative approach to studying complex physiological phenomena occurring at the cellular, organ, and phytocenotic levels. As a multidisciplinary science, plant physiology acts as a bridge between ecology, general biology, and physicochemical biology. While belonging to the botanical sciences, plant physiology maintains close ties with biochemistry, biophysics, immunology, cytology, Histology, genetics, and mathematical modeling, yet it is most closely related to animal physiology. After all, if plants and animals, like all living things, share a common origin, then all living matter must possess certain common traits, such as respiration, nutrition, irritability, and self-reproduction.

Thus, plant physiology is interconnected with biochemistry, biophysics, immunology, cytology, histology, genetics, mathematical modeling, and animal physiology, and serves as a bridge between ecology, general biology, and physicochemical biology.