There are several basic forms of plant tissue, which are formed from mostly identical cell types. The first is the epidermis. The epidermis in plants performs the same function as in animals. It is a plant tissue made up of thin, densely packaged cells designed to separate the inside of organisms from the outside. The epidermis is often covered with a waxy protective layer to prevent the plant from burning or drying out in the sun. The epidermis also contains guard cells that make a small opening called a stoma. These stoma control the passage of air and water through the leaves, allowing plants to move water and nutrients out of the soil. Through several cycles of cell division, followed by differentiation, the apical cell finally produces the germ layers, hypocotyl and radicle. The cotyledons or embryonic leaves become the first leaves of plants after germination.
Monocots tend to have a single cotyledon, while broadleaf ledons tend to have two cotyledons (in fact, the number of cotyledons present gives them the prefix « mono- » or « di-« ). The part of the plant that grows above the cotyledons is called epicotyl (« on the cotyledons »). The hypocotyl (« below the acetula ») will become the future stem, and the radicle or embryonic root will produce the future roots. Now let`s discuss these two vascular tissues one by one. Mineralized tissues are biological tissues that absorb minerals in soft matrices. Such tissues can be found both in plants and animals, as well as in algae. Typically, these tissues form a protective shield against predation or provide structural support. The lateral meristems are responsible for the secondary growth of plants. Secondary growth is usually horizontal growth. A good example would be the growth of a tree trunk in circumference. There are two types of lateral meristems to consider when studying plants.
Meristematic plant tissue differs from all other plant tissues in that it is the main growth tissue of the plant. All cells come from one or the other meristem. The apical meristem is the plant tissue that drives aerial growth and determines the direction of the plant. Root meristems burrow into the soil in search of water and nutrients. Subapical meristems divide the plant and carry the leaves in different directions. Intercalary meristems ensure growth from the center of the plant to extend the leaves upwards in sunlight. When you rotate the plants, the next plant tissue is the parenchyma. This tissue consists of thin-walled cells with very large central vacuoles. The turgor pressure of these vacuoles is increased when they are filled with water, which gives structure and support to the plant. The plant tissue of the parenchyma is found in all parts of the plant and makes up a large part of the leaves, stems and roots. In the leaves, the plant tissue of the parenchyma is strongly involved in the process of photosynthesis. All plant tissues of the parenchyma are alive and perform functions continuously.
The parenchyma tissue, when injured, can return to the meristematic plant tissue to repel damaged areas. The English word « fabric » is derived from the French word « fabric », the past participle of the verb tisser, « to weave ». Intercalary meristems are found in grasses and related plants that do not have vascular cambium or cork cambium because they do not increase their circumference. These plants have apical meristems and in areas of leaf adhesion, called nodes, they have the third type of meristematic tissue. This meristem will also actively produce new cells and is responsible for increasing length. The intercalary meristem is responsible for the regrowth of cut grass. This type of tissue consists of more than one type of cell that have a common origin and work together to perform a common function. Its function is to transport water, minerals and food to all parts of the plant.
The complex permanent tissue is of two types, the phloem is an equally important plant tissue because it is also part of the « plumbing » of a plant. First and foremost, phloem transports dissolved food substances through the plant. This piping system consists of a screen tube and accompanying cells, which are without secondary walls. The mother cells of the vascular cambium produce both xylem and phloem. These usually include fibers, parenchyma and radiation cells. Screening tubes are formed by adjacent screening tube elements. Unlike xylem container elements, the end walls have no openings. However, the front walls are full of small pores in which the cytoplasm extends from cell to cell. These porous compounds are called sieve plates. Despite the fact that their cytoplasm is actively involved in the conduction of food materials, the members of the screen tube do not have mature nuclei.
It is the accompanying cells located between the elements of the sieve tube that work in one way or another and cause the conduction of food. The tubular limbs of the living screen contain a polymer called callosis. Callose remains in solution as long as the contents of the cell are under pressure. As a repair mechanism, when an insect injures a cell and the pressure drops, callosis fails. However, callose and a phloem protein are moved through the nearest sieve plate, where they are used for a cap. This prevents further leakage of the contents of the screening tube and the injury is not necessarily fatal to the overall turgor pressure of the plant. These are stretched living cells with tiny intercellular gaps. Their cell walls consist of pectin and cellulose.
Collenchyma is present in the peripheral regions of leaves and stems and offers flexibility in the structural structure and mechanical support of plants.