Tissues in Plants
All organs of plants are made up of plant tissues. vegetal tissues; It is divided into two groups as divisible (pyggiolar-meristematic) tissue and indivisible (unchangeable) tissue.
Divided (Reptile-Meristematic) Tissues
Dividable tissue is also given names such as vermiform tissue, meristem tissue, or variable tissue. Since the cells of this tissue have the feature of mitosis, they provide elongation and thickening of the plants. Dividable tissue cells differentiate to form indivisible tissues. The characteristics of dividing tissue cells are as follows:
It is small.
Their cytoplasm is abundant.
It has a large core.
Their walls are thin.
Vacuoles are small and few in number.
Their metabolism is fast.
There are no spaces between cells.
Primary Dividable Tissue (Primary-End Meristem)
It is found at the root, trunk and branch tips. It allows the plant to grow in length throughout its life. Therefore, the growth in plants is unlimited. Since the primary meristem tissue at the root and stem ends is cone-shaped, it is called a growth cone. Young leaves protect the growth cone on the stem and the caliptra (thimble) on the root. This tissue, which enables the plant to grow in height, also forms the basis of indivisible tissues.
Secondary Dividable Tissue (Secondary Meristem) (Cambium)
It is formed by the ability of non-dividing tissue cells to subsequently divide. The secondary meristematic tissue is also called the cambium. Cambium is found in dicotyledonous perennials and conifers. The cambium allows the plant to grow transversely. It is two kinds.
Inner cambium: It forms vascular bundles in plants every year in spring and autumn. The number of these bundles allows the age of the plant to be calculated.
Outer cambium: In perennial plants, the epidermis on the stem breaks down in the second year. Fungal tissue is formed instead.
Indivisible Textures
Cells that make up divisible tissue change over time to form indivisible tissues. The characteristics of indivisible tissue cells are as follows:
Cells have lost their ability to divide.
Some cells are dead.
The cell wall is thick.
The vacuoles are large.
Cells have little cytoplasm.
There are spaces between cells.
Indivisible tissues are divided into five groups according to their structure and functions. These; basic tissue, protective tissue, supporting tissue, vascular tissue and secretory tissue.
Parenchyma Tissue (Basic Tissue)
Parenchyma tissue fills between other tissues. Parenchyma cells are thin-walled, abundant cytoplasm and viable. Parenchyma tissue is of four types.
Assimilation parenchyma: It is found in the light parts of the plant, especially in the leaves. The assimilation parenchyma, which plays a role in photosynthesis, is located in the mesophyll layer of the leaf. The mesophyll layer consists of two parts, the palisade and the sponge parenchyma. Palisade parenchyma cells are under the epidermis. Cylindrical, with abundant chloroplasts; frequently and regularly. Sponge parenchyma cells have less chloroplasts. They are arranged irregularly and there are spaces between them.
Conduction parenchyma: It is located between the assimilation parenchyma and the vascular bundles. Cells do not have chloroplasts. The task of the conduction parenchyma is to ensure the transmission of water, mineral salts and organic nutrients between the photosynthesizing tissues and the vascular bundles.
Storage parenchyma: Found in roots, stems, seeds and fruits of plants. It stores nutrients and water. For example; There is parenchyma that stores water in cactus, oil in olives and starch in potatoes.
Ventilation parenchyma: Found in the roots and stems of marsh and aquatic plants. There are large spaces between the cells. Air is stored in these spaces.
Protective Tissue
It covers the roots, stems, leaves and fruits of plants and protects the underlying tissues against external factors. It consists of thick-walled cells without chlorophyll. It regulates the gas exchange and water loss of the plant. The protective tissue is divided into two.
Epidermis: It is formed by the differentiation of the outermost cells of the dividing tissue. The epidermis is the protective tissue of the stems and leaves of all plants throughout life.
The characteristics of epidermis cells are as follows:
It usually consists of a single row of cells.
There are no spaces between cells.
Cells do not have chloroplasts.
Above the epidermis is the cuticle layer. The cuticle prevents the plant from losing water. It is found above ground. It is not found in the root. The thickness of the cuticle layer varies according to environmental factors. The cuticle layer is thick in plants living in arid regions, and thin in those living in humid regions.
Epidermis cells differentiate to form hairs, spines and stomata. Some of the epidermis cells extend outward to form hairs. Feathers are of various shapes and structures and undertake different tasks. It performs the functions of sucking in roots, defense in nettle, secretion in mint, and holding in ivy.
With the differentiation of some epidermis cells in the leaves and young stems, pores (stomas) are formed. The stomata are like two beans, facing each other. The walls of the facing surfaces of the stomata are thick, and the outer parts are thin-walled. Depending on the turgor pressure, the stomata open or close. Stomatal cells contain chloroplast organelles. These cells carry out photosynthesis. It regulates gas exchange and water loss by opening and closing.
The location and number of stomata vary according to the plant’s living conditions and genetic characteristics. It is usually found in the lower epidermis of the leaf in land plants, and in the upper epidermis of the leaf in aquatic plants. In arid climate plants where water loss is high, stomata are few and deep. It is found in large numbers and close to the surface in humid region plants.
Fungal tissue: In perennial plants, the epidermis in the root and stem is broken down in the second year. The epidermis is replaced by cork tissue, which consists of the cork cambium. Multilayered cork tissue cells are dead. The cells are filled with air and are waterproof. There are cavities that provide gas exchange between the cork tissue. The cavities are constantly open and appear as rounded bumps on the body surface.
Support Tissue
Plants have to protect themselves against external influences in order to maintain their vitality and preserve their structures. Tissues that give shape and support to plants are called supporting tissues.
Cellulose wall and turgor pressure act as support in herbaceous plants. In perennial plants, hard tissue and hard tissue serve as support.
Many tissues (Collenchyma): Found in the growing parts of young plants, in flowers, leaves and fruit stems, and in the stems of some herbaceous plants. Many tissue cells are alive. There is thickening of the cell walls. Thickening is provided by cellulose and pectin deposited on the wall. If the thickening is at the corners of the cell wall, it is called the corner collenchyma, and if it is all over the cell wall, it is called plate collenchyma.
Hard tissue (Scleranchyma): Cells are dead because their cytoplasm and nuclei are lost due to thickening of the cell walls. divided into two according to their shape.
Stone cells: Their width and length are equal to each other.
Hard tissue threads: They are spindle-shaped cells with two ends.
Transmission Tissue
Conduction tissues are found in all plants except non-vascular plants. It provides the transport of substances between the root and the leaf. Wood and bark pipes form the vascular tissue.
Wood pipes: Cells made up of dividing tissue overlap and lose their nucleus and cytoplasm over time. Wood pulp accumulates in the cell wall and causes thickening. Membranes between cells dissolve and disappear. Thus, wood pipes are formed with the characteristics of capillary pipes. Wood pipes consist of tubular cells and cells called tracheids and parenchyma and sclerenchyma cells adapted to these cells. The connection to the side pipes is provided by a large number of passages. Wood pipes are found in bundles.
The characteristics of wood pipes are as follows:
Cells are non-living.
Transport in wood pipes is one-way.
Water and mineral substances are transported.
Transport is fast.
Peel pipes: They are formed by lining up the living cells in a single line on top of each other. The cells that make up the conduction bundle become longer, vacuoles form, and the cytoplasm and nuclei move aside. Holes form in the membranes between overlapping cells. This perforated structure is similar to a griddle. For this reason, peel pipes are also called sieve pipes. Features of peel pipes:
Cells are alive.
Transport in Soymuk pipes is bidirectional.
It carries the photosynthesis products synthesized in the leaves to the other parts of the plant, and the organic materials taken from the soil to the leaves.
Transport is slow.
Secretory Tissue
Secretory tissue cells are found among the various tissues of the plant in a collective or individually dispersed state. The characteristics of secretory tissue cells are as follows:
They have abundant cytoplasm.
Their nuclei are large.
Their vacuoles are small.
Secretions are sometimes deposited inside the cell. The cell, in which secretion accumulates, loses its vitality over time. Sometimes the secretion formed in the cell is thrown out of the cell. The secretory tissue can be a large cell, or it can be in the form of a secretory pocket or glandular tube consisting of many cells.
The functions of the secretory tissue are as follows:
As in stinging nettle, it secretes caustic and provides protection.
In insectivorous plants, digestive secretions provide the digestion of insects.
Honey extract secreted from flowers attracts insects and provides pollination.
Some secretions provide protection from decaying microorganisms.
The secretions in poppy and rubber help the wounds to be repaired.
Some secretions allow the plant to be eaten by animals.
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