A cell is the basic structural and functional unit of life.
A group of cells that are similar in structure and perform the same function is called a TISSUE. Like animals, the plant is also made up of different kinds of tissues. These tissues are mainly classified into two types based on the cell’s ability to split or not. They are Meristematic tissues and Permanent tissues.
A group of cells that are in a state of division are known as Meristematic tissues.
The properties of Meristematic tissues are:
2.Capable of cell division
3.Helps in the growth of plants.
A group of cells that do not bifurcate further and are distinguished based on the functions the tissues perform.
The Properties of Permanent Tissues are:
2. Incapable of cell division.
3. Performs particular function.
The figure given below, depicts the types of plant tissues.
Based on the location, Meristematic tissues can be classified as:
1. Apical Meristem : Helps in primary growth.
SAM(shoot apical meristem):Gives rise to organs like leaves and flowers.
There are many Shoot apical meristem theories like; Apical cell theory,Histogen theory and Tunica corpus theory.
RAM(root apical meristem):Helps in the growth of future roots.
There are many root apical meristem theories like; Apical cell theory,Histogen theory and Korper-Kappe theory.
They are present in the apices of primary and secondary shoots of plants.
They are responsible for increase in length and all primary tissue which originates from them.
2. Lateral Meristem : Helps in the secondary growth.
Present along the sides of the stem.
Vascular cambium is present in gymnosperms(seed bearing plants) and angiosperms(flower bearing plants) that are are good examples for lateral meristems.
Eg: Cork(located below the bark of stem) and vascular cambium(located in vascular tissues).
Intercalary Meristem : Present at internodes or regions of stem between the places where the leaves are attached. It helps in the growth of leaves, and stems.
1. Promeristem: The region of new growth that is present in the apices of shoots and roots where the organs form their foundation.
2. Primary meristem: First derivative of meristem which forms the basic parts of the plant.
3. Secondary meristem: Meristem which appears at the later stages of development of the plant organ.
1. Protoderm: It is the outermost layer of the meristematic layer which later develops into hair, and stomata.
2. Procambium: Meristem which develops into primary vascular tissues like xylem and phloem.
3. Ground meristem: Meristem which follows the ground tissue system and forms hypodermis, cortex, pith, pericycle, and medullary rays.
1. Dermatoger: The outermost layer of the histogen that forms the epiblema and epidermis in the root.
2. Periblem: The middle layer of histogen which forms the endodermis and the cortex.
3. Plerome: Histogens that form vascular strands like the pith, vascular bands, etc.
Meristematic cells that split up, extend, become differentiated, and perform particular functions are called permanent tissues.
There are two types of permanent tissues; simple and complex:
Simple Tissue: Dermal and ground tissues.
1. Dermal Tissues:
Form the outer layer of plant parts.
Cells of this tissue are elongated and flattened.
Intercellular spaces are absent.
They provide protection against adverse environmental conditions and predatory attacks. Therefore dermal tissues are also called protective tissues.
The gaseous exchange through stomata is achieved by this tissue.
The epidermis (outermost layer of plant body), and Cork (Light and thin layer chipping off from bark) constitutes the dermal tissue.
Note: The CUTICLE-Epidermis covering is made of a waxy substance called cutin.
2. Ground Tissues (Supporting plant tissues):
The main function of ground tissues is to provide support, strength, and flexibility to plants.
The Three Types of Ground Tissues are:
Vascular Tissues: Xylem and Phloem. These tissues are also known as conducting tissues because of their important role in water and food transportation. (image will be uploaded soon)
Xylem is called primary xylem if its elements are derived from procambium of apical meristem.
Xylem is called secondary xylem if its elements develop from vascular cambium during the process of secondary growth.
There are four types of Xylem based on the position of protoxylem with respect to metaxylem. They are as follows:
1. Exarch: Protoxylem located outside the metaxylem.
2. Mesarch: Protoxylem located in the middle of the metaxylem.
3. Centrarch: Protoxylem located in the center of the metaxylem.
4. Endarch: Protoxylem located inside the metaxylem.
Phloem is also known as Bast because it is also used for binding purposes. Eg; Hemp and flax.
The meristematic cells keep on bifurcating.
Meristematic tissues based on their location are of three types namely; apical, lateral, and intercalary meristematic tissues.
Permanent tissues are of two types: Simple and Complex.
Dermal or protective tissues are simple tissues. They form the outer covering of plant parts such as the stem, roots, fruits, flowers etc. The epidermis and cork are two types of dermal tissues.
The main function of the ground tissue is to provide support, strength, and flexibility to plants. The three types of ground tissues are; Parenchyma, Collenchyma, and Sclerenchyma.
Vascular tissues are also called conducting tissues as they play an important role in the transportation of water and food in plants.
Xylem is a water conducting tissue.
Phloem is a food conducting tissue.