Electron microscopic cross section of mesofillum cells 

garden beans (Phaseolus vulgaris)

The cell wall is 0.1 μm thick; the diameter of the nucleus is 3 μm and the cell is approximately 10 μm
long

It is important to note that the link mechanisms between the individual cellular compartments and compartments, which are mainly biochemical (through diffusion through semipermeable membranes and membrane proteins), allow the cell to function as a unified system despite compartmentalization.

2.1. The Cytoskeleton (Cytoskeleton)
Cell cytoskeleton (cytoskeleton) provides spatial separation of cellular constituents and plays a fundamental role in mitosis, meiosis, cytoplasmic proliferation (cytokinesis), cell wall formation, cellular retention, cell differentiation, and intracellular plasma movements. Plant cells contain two cellular backbones: microtubules and microfilaments. Microtubules are hollow ("tube") tubular formations of 20-25 nm diameter, built up by proteins called actin and tubulin.

Microfilaments are compact, with a diameter of 4-7 nm and are made up of actin proteins. A microtubule is made up of hundreds of thousands of α- and β-tubulin units. A microfilament consists of two twisted actin fibers
I.2. Vertical view of microtubules and microfilaments of two actin fibers: from a microtubule vertical view. Each microtubule consists of 13 profiles. The figure shows the organization of the α and β subunits
Tubulin and actin are reversibly transformed into chains and break apart. Formation and degradation are continuous: at one end of the chain there is formation and the other at the end; its speed also depends on the concentration of the individual formations and other factors, such as calcium ion concentration. Thus, there is a dynamic balance within the cell between free and bound tubulin.
I.3. - Preprophic microtubule bundle section in Azolla root cell. Scale = 1.0 mm (based on Gunning-Hardham-Hughes 1978)
Microtubules play an important role in cell division, because the mitotic spindle in the mitotic spindle forms the tensile yarn (Figure I.3). At the end of the drawstring is the so-called. microtubule-organizing center, which is the place of microtubule formation. A part of the microtubules is called the so-called microtubules. linked to the central region of chromosomes. (Central region of chromosomes: the primary ligation of the metaphase chromosomes along which the chromosomes bend and are divided into arms, they are called centromers or kinetics. They are also considered to be the center of chromosome motion, as they adhere to the torsion threads of the spindle and migrate to the chromosomes. The cytokinesis - which takes place in the last phase of mitosis - transforms the cell into two progeny cells. The progenitor cells first produce a pectin-rich cell plate. There are two steps in the formation of cell plates in higher plants. In the first step, Golgi vesicles and ER cysts are aggregated at the boundaries of the two progeny cells. Then, in the second step, the vesicles merge, and the materials delivered in the ER cisterns are precursors to the newly formed cell wall.

Short overview of general structural changes in cell division: At the end of the G2 section of the interface, the ring-like formation around the nucleus is called a preprofusion bundle (PPB), which plays a crucial role in the formation of the middle plate between the two progeny cells. At the beginning of the profase, the microtubule subunits are repolymerized and organized into tensile strands, each having a microtubule-organizing center (MTOC) that performs the function of the centriolum. At the end of the anaphase, or at the beginning of the telophase, a complex is formed from the dissociated fusion subunits and the membranes of the endoplasmic reticulum, called fragmoplast. The latter is delivered with pectin-containing Golgi vesicles, which are organized into a tubular vesicular network (central plate). Cellulose is incorporated into the tubular network, and the two progeny cells are physically separated from each other by a common wall (primary cell wall).

The well known compound that inhibits cell division, the mitochemical inhibitory effect of colchicine, is due to the special binding of the alkaloid to free tubulin, thereby inhibiting the growth of microtubules. In addition, other functions of microtubules are limited by this poison. Microfilaments play an important role in the movement of cellular constituents and in the formation of pollen hoses (see pages 113 and 131).