The higher plants have multicellular bodies made up of various kinds of cells. These cells cluster together to perform specific functions. A group of plant cells having common origin and similar in structure and function is known as plant tissue. Most of the plant tissues are dead. Most of the tissues in plants are supportive, need less energy and maintenance. The growth of plant is indefinite. Plants grow throughout their life with the help of certain tissues
located in certain regions in the body. The structural organization of organs and organ system are less specialized than animals. Thus, plant tissues are adapted for sedentary existence. On the basis of division, the plant tissues have been classified into two types:
Meristematic tissue is a group of young cells that have the capacity of active cell division or retain the power of cell division. This tissue is found in all the growing parts of a plant such as root tip, shoot tip, etc. The cells of meristematic tissues divide continuously and help in increasing the length and girth of the plant. This tissue differentiates to give rise permanent tissue. Thus, meristematic tissue is a group of young cells which are located at growing regions and divide continuously to add new cells to the plant body.
Occurence
Meristematic tissues are found in growing parts such as tips of roots, stems and branches. It is also present between the bark and the wood of trees where it leads to the increase in thickness of stem.
Characteristics
Depending upon the occurrence and position in the plant body, meristems are divided into three categories. They are apical, lateral and intercalary.
(a) Apical meristem: The apical meristems are present at the tips of stem, root and their branches. Due to growth of apical meristems, the stems and roots increases in length. Examples: root apical meristem and shoot apical meristem.
(b) Intercalary meristem: This is the part of apical meristem which gets separated from the apex due to development of permanent tissue in between. The intercalary meristems are usually present at the base of node, base of inter node or at the base of the leaf. They are responsible for elongation of the organs.
located in certain regions in the body. The structural organization of organs and organ system are less specialized than animals. Thus, plant tissues are adapted for sedentary existence. On the basis of division, the plant tissues have been classified into two types:
- Meristematic Tissue
- Permanent Tissue
Meristematic tissue is a group of young cells that have the capacity of active cell division or retain the power of cell division. This tissue is found in all the growing parts of a plant such as root tip, shoot tip, etc. The cells of meristematic tissues divide continuously and help in increasing the length and girth of the plant. This tissue differentiates to give rise permanent tissue. Thus, meristematic tissue is a group of young cells which are located at growing regions and divide continuously to add new cells to the plant body.
Occurence
Meristematic tissues are found in growing parts such as tips of roots, stems and branches. It is also present between the bark and the wood of trees where it leads to the increase in thickness of stem.
Characteristics
- They are living cells and are very active.
- The cells are similar in structure and may be rounded, oval, polygonal or rectangular in shape.
- Each cell contains a prominent nucleus and dense cytoplasm.
- Cell walls are thin and cellulosic.
- Vacuoles are generally absent.
- Cells are compactly arranged generally without intercellular spaces between them.
- They are capable of dividing indefinitely. New cells produced by meristematic tissues are initially like those of meristematic but later on as they mature and grow; they become differentiated as components of other tissues.
- They do not store reserve food materials.
Depending upon the occurrence and position in the plant body, meristems are divided into three categories. They are apical, lateral and intercalary.
(a) Apical meristem: The apical meristems are present at the tips of stem, root and their branches. Due to growth of apical meristems, the stems and roots increases in length. Examples: root apical meristem and shoot apical meristem.(b) Intercalary meristem: This is the part of apical meristem which gets separated from the apex due to development of permanent tissue in between. The intercalary meristems are usually present at the base of node, base of inter node or at the base of the leaf. They are responsible for elongation of the organs.
(c) Lateral meristem: Lateral meristem occurs on the sides and is responsible for the increase in diameter of the plant roots and stem (girth). The lateral meristem usually occurs beneath the bark in the form of cork cambium and in vascular bundles of dicots in the form of vascular cambium. These tissues are also responsible for growth in thickness by the addition of secondary tissue. This phenomenon is called secondary growth.
2. Permanent Tissue
A permanent tissue is a group of cells which have lost their capability of division. They have definite shape, size and thickness. The permanent cells may be dead or living thin walled or thick walled. Permanent tissues are formed by the growth of meristematic tissue. The process of taking up of a permanent shape, size and function is called differentiation. Permanent tissues are formed by the differentiation of cells of meristematic tissue. On the basis of function, permanent tissues are categorized as simple permanent and complex permanent. Simple permanent consists of parenchyma, collenchyma and sclerenchyma.
Complex permanent tissue consists of xylem and phloem. Xylem is mainly responsible for the conduction of water and minerals. It also provides mechanical support to the plant. Phloem is responsible for transport of food prepared by leaves to other parts in the storage tissue of the plant.
2. Permanent Tissue
A permanent tissue is a group of cells which have lost their capability of division. They have definite shape, size and thickness. The permanent cells may be dead or living thin walled or thick walled. Permanent tissues are formed by the growth of meristematic tissue. The process of taking up of a permanent shape, size and function is called differentiation. Permanent tissues are formed by the differentiation of cells of meristematic tissue. On the basis of function, permanent tissues are categorized as simple permanent and complex permanent. Simple permanent consists of parenchyma, collenchyma and sclerenchyma.
Complex permanent tissue consists of xylem and phloem. Xylem is mainly responsible for the conduction of water and minerals. It also provides mechanical support to the plant. Phloem is responsible for transport of food prepared by leaves to other parts in the storage tissue of the plant.
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