Plants, just like animals are multicellular eukaryotes. This means that they consist of cells, tissues, and organs each with a special unique function to carry out. A cell is the smallest building block of any organism. A group of cells together forms a tissue, and a group of tissue combine to form an organ. Plants belong to the Plantae kingdom, which consists of all organisms which are not plants including fungi and algae.
The plant tissue system is broadly divided into two types: meristematic tissue and permanent tissue(non-meristematic tissue). The meristematic tissue consists of undifferentiated cells(meristematic cells) capable of cell division. These cells can further develop into other tissues and organs that are found in plants. These cells continue to divide till they lose the ability to divide any further and become differentiated. Differentiated plant cells can not divide any further or produce any more cells.
Permanent tissue is defined as a group of living or dead cells formed from the meristematic tissue that has now lost the ability to divide and now have become fixed at a place permanently. These plant tissues take up a specific role after they have lost the ability to divide. The process by which they lose their ability to divide and retain a permanent shape and size and perform a specific function is known as cellular differentiation. They are further divided into two types: Simple Permanent Tissue, Complex Permanent Tissue.
Simple Permanent Tissue
These tissues are also known as homogeneous tissue. They consist of only a single type of cell which has the same origin, structure, and function. They are again classified into three main types:
Parenchyma
The name comes from the Greek words para and enchyma which means beside and tissue respectively. It consists of unspecialized living cells with thin cells. These cells are loosely packed so there are intercellular spaces present in between them. They are generally oval or round in shape. They contain a small number of vacuoles, sometimes it is nonexistential. This is found in all plants and is responsible for the transportation of food and water. The reproductive cells in plants are also Parenchyma.
Characteristics of Parenchyma
- They are found in all plants.
- The cells in the Parenchyma tissue are living.
- The cell walls of Parenchyma tissue are very thin and are made up of Cellulose.
- They are generally oval or round in shape.
- In the center of the cell, there is a large Vacuole.
- There are intercellular spaces present between the cells in this tissue.
- These cells have the ability to multiply after they have matured, this property is helpful in the regeneration of damaged plant cells.
Functions of Parenchyma tissue
- These tissues are suitable for storage due to the large intercellular spaces in between them. These tissues can store water, fats, oil, etc.
- They are capable of transporting nutrition and other chemical products formed in the plant. Some cells are also capable of transporting light through them.
- This tissue is responsible for photosynthesis and thus for the general well-being of the plant.
- They convert to another type of cell when required for some specific function.
- These cells have the ability to multiply after they have matured, this property is helpful in the regeneration of damaged plant cells.
Collenchyma
The name comes from the Greek words colla and enchyma which means gum and tissue respectively. It consists of thin-walled cells. These cells are made up of cellulose and pectin. Due to the presence of pectin, the refractive index of these cells is very high. These cells are very closely packed so there are no intercellular spaces present in this tissue. These tissues are present in the epidermis and vascular bundle of the dicot leaf.
Characteristics
- The cells of collenchyma are elongated and spherical or oval in shape.
- These cells contain a primary cell wall.
- These cells are alive when they mature but not after that.
- These cell walls are thick due to the deposition of cellulose and pectin on the cell walls. This thickness is not evenly distributed as the cell wall is thick mostly at the corners but not at the center.
- All these cells are arranged very closely so intercellular spaces are not present in this tissue.
- The main purpose of these tissues is to provide mechanical support to plants.
Functions
- The main purpose of collenchyma is to provide flexibility and support plant growth.
- It is mostly present in the growing parts of the plant.
- It contains chloroplast and is considered responsible for photosynthesis.
- The purpose of collenchyma is to protect leaf margins from tearing.
Sclerenchyma
The name comes from the Greek words Sclerous and enchyma which means hard and tissue respectively. It mostly consists of thick-walled dead cells. They are hard and extremely thick and are uniformly distributed. The main purpose of this is to provide mechanical support. There are no intermolecular spaces present between the tissues. The cell walls become thick due to the deposit of lignin. It is found in shells of nuts, fibers, wood, etc.
Characteristics
- It mostly consists of long and narrow cells.
- Most of these cells are dead and can not multiply.
- The cell wall is thick. They have both primary and secondary cell walls. The secondary cell wall is very thick and has pits that allow the transfer of gases.
- The secondary cell walls are made up of cellulose and pectin.
- After the cells mature they are mostly dead and they lose the ability to multiply and stretch.
Functions
- The main purpose of Sclerenchyma tissue is to provide mechanical support to the plant.
- They are present in the protective covering of nuts and seeds.
- The xylem vessels and tracheids are also a part of Sclerenchyma tissue.
- They form a waxy coating around the leaves to reduce water loss.
Complex Permanent Tissues
Complex Permanent tissues consist of more than one type of cells which have a common origin and which are working together for a common goal as a unit. The main purpose of these complex permanent tissues is the transportation of water and minerals, these tissues are also known as conducting and vascular tissues. It is further divided into two types:
Xylem
The name comes from the Greek word xylos which means wood. It acts as the chief conducting tissue for the plants. It is responsible for the transportation of water and other inorganic solutes. It is divided into tracheids, vessels, xylem fiber, and xylem parenchyma. They are mostly present vertically but they are even present horizontally.
Characteristics
- It consists of only living cells.
- It has a cell wall, it is very thin and it is made of cellulosic.
- These cells have a nucleus and protoplast. These cells are colorless and have large vacuoles.
- The nucleus and cytoplasm of xylem tissue migrate into tyloses. Tyloses stores various substances and have a possibility of developing secondary cell walls. The cells which give rise to tyloses are called contact cells.
Functions
- The main purpose of xylem tissue is the storage of food materials like starch, fats, and tannins.
- They are instrumental in the transportation of water.
- When there is a scarcity of water, it helps to reduce damage to the vascular tissues.
- They are responsible for repairing and restoring the vessels whenever there is any blockage or formation of air bubbles.
Phloem
The phloem is used to transport food minerals that are dissolved in water. The phloem transports food and minerals both upwards and downwards. It is divided into a sieve tube, Companion cell, Phloem fiber, and Phloem parenchyma.
Characteristics
- The cells in the phloem are alive.
- It consists of an elongated, tubular structure.
- The cell walls are very thin.
- Helps in translocation.
- It consists of a sieve tube, companion cell, phloem fibers, and phloem parenchyma.
Functions
- Carbohydrates produced during photosynthesis are stored in tubes or bulbs which are made of phloem.
- The phloem transports sap.
- Helps in translocation.
- They provide mechanical support to the plants.
Special Permanent Tissues
These tissues are modified structurally and are organized in a particular manner to perform a specific function. For example one of the functions of special permanent tissue is the secretion of some materials like latex. It is further divided into two sub-parts Laticiferous tissues and Glandular tissue.
Glandular Tissue
They are made up of different types of glands. All these lands are formed by single cells or groups of similar cells. The main function of these tissues is to secrete resin, oil, etc. These glands are situated on the epidermis.
Laticiferous Tissues
This is a plant tissue that is responsible for the production and secretion of latex. They are originally formed from meristematic tissue and once they mature they convert to perform specific functions. These tissues consist of thin-walled, elongated cells with multiple nuclei.
FAQs on Permanent Tissue
Question 1: What are the Special Permanent tissues?
Answer:
These tissues are modified structurally and are organized in a particular manner to perform a specific function. For example one of the function of special permanent tissue is secretion of some materials like latex. They are originally formed from meristematic tissue and once they mature they convert to perform specific function. These tissues consist of thin-walled, elongated cells with multiple nuclei.
Question 2: How is the Plant tissue system divided?
Answer:
A cell is the smallest building block of any organism. A group of cells together forms a tissue, and a group of tissue combine to form an organ. The plant tissue system is broadly divided into two types: meristematic tissue and permanent tissue(non-meristematic tissue).
Question 3: Define Meristematic tissue.
Answer:
The meristematic tissue consists of undifferentiated cells (meristematic cells) capable of cell division. These cells can further develop into other tissues and organs that are found in plants. These cells continue to divide till they lose the ability to divide any further and become differentiated.
Question 4: Define Permanent tissue.
Answer:
Permanent tissue is defined as a group of living or dead cells formed from the meristematic tissue that has now lost the ability to divide and now have become fixed at a place permanently. These plant tissues take up a specific role after they have lost the ability to divide. The process by which they lose their ability to divide and retain a permanent shape and size and perform a specific function is known as cellular differentiation.
Question 5: Explain the classification of complex permanent tissues.
Answer:
The main purpose of these complex permanent tissues is the transportation of water and minerals, due to these tissues are also known as conducting and vascular tissues. It is further divided into two types:
- Xylem: It acts as the chief conducting tissue for the plants. It is responsible for the transportation of water and other inorganic solutes. It is divided into tracheids, vessels, xylem fiber and xylem parenchyma.
- Phloem: The phloem is used to transport food minerals that are dissolved in water. It transports food and minerals both upwards and downwards. It is divided into a sieve tube, Companion cell, Phloem fiber, and Phloem parenchyma.