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

2. Structural Components of the Plant Cell
2.1 Structural and Functional Organization of the Plant Cell

The Cell is the fundamental Structural and functional unit of life, exhibiting all The properties of a living system: METABOLISM and Energy conversion, GROWTH AND DEVELOPMENT, irritability, self-reproduction, and self-regulation. In nature, a cell can exist either as an independent Organism or as part of a multicellular one. Despite the wide variety of shapes and Functions they perform, Cells of All living organisms share a similar structural Organization.

The Discovery of the cellular Structure of organisms was made possible by the invention of the Microscope in 1665 by the English scientist Robert Hooke, who observed a thin slice of cork and saw compartments that he named cells. The term "cell" is derived from the Greek word "cytos" (cell) or the Latin "cellula" (small room/cavity). As a general biological concept, the Cell Theory was first formulated by German scientists: the zoologist Theodor Schwann and the botanist Matthias Schleiden (1837–1838). Schleiden, studying plants, proved that their Tissues are composed of cells. Schwann established that animal tissues are likewise formed by cells. The Cell theory played a crucial role in establishing THE CONCEPT OF The Unity of life and the common origin of PLANT AND ANIMAL organisms, and it served as the theoretical foundation for Charles Darwin's theory of evolution.

There are two principal levels of Cellular Organization: prokaryotic and eukaryotic.

The Introduction/4.html">Prokaryotic Cell type refers to cells that lack a true, membrane-bound nucleus. Instead, their genetic material is represented by a nucleoid—a circular DNA molecule not separated from the Cytoplasm by a nuclear envelope. The eukaryotic type, or eukaryotes, includes cells of unicellular and Multicellular Organisms that possess a karyolemma (nuclear membrane) and DNA molecules packaged by Protein Complexes into Chromosomes, featuring a multireplicon system of DNA Replication. Plant cells typically range in size from 10 to 600 µm. Based on their shape, cells are divided into parenchymatous and prosenchymatous (where length exceeds width by 5–10 times).

Plant cells are characterized by the following features:

1. The presence of a polysaccharide (Cellulose) Cell wall;

2. The presence of Plastids, associated with the phototrophic mode of Nutrition in plants;

3. The presence of a large vacuole, which plays a key role in maintaining turgor pressure;

4. The absence of centrioles during Cell Division.