Permanent Tissues

Permanent tissues are groups of similar cells that have lost the capability to differentiate; that is, in simpler words, cells of permanent tissues have taken up a particular shape and size through a process known as differentiation. Cells of permanent tissue cannot divide or differentiate. Permanent tissues are formed from meristematic tissues and in the course of development, these meristematic tissues are fixed at a particular location. 

Types of Permanent tissues

• Permanent tissues are divided into two categories: simple permanent tissues and complex permanent tissues.
• Simple permanent tissues are tissues that are clusters of cells that have the same structure, same origin and same function.
• Complex permanent tissues are tissues that are clusters of different types of cells but with a similar origin.

Simple permanent tissue

Simple permanent tissues are tissues made up of similar types of cells that perform the same function and are of the same origin. They are further divided into three types:

Parenchyma – Parenchyma tissue is a cluster of non-specialized cells. These cells are living cells with thin cell walls. The cells of parenchyma tissue are packed in such a way that there are intercellular spaces between the cells. The cells are polyhedral in shape. The cells may or may not contain vacuoles, and even if vacuoles are present in the cells, they are small in number.

Function

• Parenchyma tissues are known to store food products as well as support plants.
• There are some specialised types of parenchyma with special functions, like Chlorenchyma which contains chlorophyll to perform photosynthesis.
• Aerenchyma is characterised by a large air cavity that keeps plants afloat on water and provides buoyancy to the plants.
• Idioblast cells are specialised parenchyma cells that are known for storing metabolic wastes.
• Prosenchyma, a type of succulent parenchyma, are spindle fibre-shaped and provide support.
• Xerophytes also have parenchyma tissues that are known to store water.

Collenchyma – They are tissues made up of living thin-walled cells but have deposits of cellulose, pectin etc. at the edges of the cells. The cells of this tissue are arranged compactly with little or no space between them. Due to this accumulation of cellulose and arrangement of the cells in the tissues, they are mainly found in stems and leaves but are absent in roots and monocots.

Function:

• Due to the arrangement and accumulation of cellulose in the cells, the collenchyma tissue provides high tensile strength to the plants.
• They often help in producing and storing starch.
• Its presence in leaves provides resistance to leaves from the winds.
• They also provide elasticity to the plants.

Sclerenchyma -They are the only tissue made up of dead cells that are thick-walled, and protoplasm is completely absent. They have a high amount of lignin in the cells. Due to lignin, the cell walls become impermeable to water; this is known as sclereids. Intermolecular space between the cells is absent.  Sclerenchyma tissue is also of two types, one being a sclerenchyma fibre and the other being sclereids.

Function:

• This tissue provides strength to the plant body.
• Sclerenchyma fibre is often used as ropes.
• Sclereids are found in legumes, etc.

Complex permanent tissues

Complex permanent tissues are made of different types of cells. They are further divided into two types: Xylem and Phloem.

• Xylem – it is a tissue mostly made up of non-living cells. They are known for transporting water from roots to the whole plant body. It consists of four different types of cells: Xylem fibre, Xylem Parenchyma (Living), Tracheids and vessels.
• Phloem- is a tissue made up of living cells. They are known for translocating food materials from leaves to other parts of the plant. It consists of four types of cells namely sieve tube, companion cell, phloem fibre (dead cells) and phloem parenchyma.

Conclusion

Tissues are made of cells that can be of the same type or different. Permanent tissues are tissues made up of cells that have lost their capacity to divide and differentiate into another type of cell. They generally develop from meristematic tissues that have lost their property to move, differentiate or divide. Permanent tissues are further divided into two different types: simple permanent tissues and complex permanent tissues. All the types of permanent tissues have different functions like providing strength, support and storing food, etc.