Plant Physiology - Musienko, M. M. 2001

Chemical and molecular composition, structure, and functions of the plant cell
From the history of the development of cell theory

The Structural and functional unit of a plant Organism, like that of any other living creature, is the Cell. This term was first proposed in 1665 by Robert Hooke, who studied The Structure of cork under a Microscope. Later, in the 19th century, zoologist T. Schwann and botanist M. Schleiden formulated the general biological Concept of the Cell Theory, which postulated that The Cell is the fundamental unit of Structure and function in all organisms. According to modern understanding, the cell is the basic structural and functional unit of All living organisms, as well as an elementary living system. Only Viruses represent non-Cellular forms of life. D.I. Ivanovsky (1864–1920) was the first to discover colorless crystal-like clusters within the Cells of tobacco leaves—the causative agents of tobacco mosaic disease, which were later named viruses. They lack a cellular structure; at the same time, they exhibit A number of characteristics inherent to living organisms. Thanks to his work, plant physiology gave birth to a new branch of science—virology. It is worth noting that D.I. Ivanovsky defended his dissertation on The Nature of tobacco mosaic disease in 1903 at the University of Kyiv, where in 1962, under the supervision of N.P. Kornyushenko, the first department of virology in Ukraine was established, and where research on plant viruses is currently being successfully pursued by Academician of the UAAS A.L. Boyko.

Viruses exist on the boundary between the living and the non-living, which once again reminds us of the existence of a continuous chain of steadily increasing complexity, beginning with molecules and culminating in complex, closed cellular systems.

To describe the living contents of cells, R. Brown introduced METABOLISM/2.html">THE CONCEPT OF the Nucleus (1831), J. Purkinje the protoplasm (1840), and E. Strasburger the Cytoplasm (1882). The cytoplasm, which fills the entire internal space in most cells, contains a number of Organelles and various dissolved substances.

The cell is the logical starting point for The Study of any organism. The entire diversity of plant cells can be divided into two groups: cells that support metabolism and those lacking metabolic activity. The most active are parenchyma cells, which account for- 26

80% of all cells in a plant organism. Essentially, every living cell is a self-replicating chemical system surrounded by a Plasma Membrane (Plasmalemma), which controls the Transport of substances and ensures the Structural and Biochemical Isolation of the cell. By regulating the exchange between the internal and external environments, it maintains the stability (Homeostasis) of the system.

Every cell contains DNA that encodes Genetic information. The Genetic Code is universal across all organisms, which are divided into prokaryotes (pre-nuclear) and eukaryotes, in which DNA is bound to Proteins and organized into Chromosomes housed within a nucleus. Eukaryotic cells are partitioned into compartments by means of membranes.