Permanent Tissues

The tissues which might be completely grown and feature the misplaced potential for division are referred to as permanent tissues. The meristematic tissues divide and differentiate to shape the permanent tissues.

Till now, we have studied that the cells of primary and secondary meristems undergo division and differentiation to produce primary and secondary permanent tissues of the plant body respectively. Now, the new cells which are formed following the divisions of cells of primary and secondary meristems; become structurally and functionally specialised and lose the ability to divide. These newly formed cells are called permanent or mature cells and tissues formed by these cells are called permanent tissues. These mature or permanent tissues perform specific functions in the body of plants. This phenomenon leading to maturation of plant cells is called differentiation. Hence, we can say that the meristematic cells differentiate’ to form the permanent cells.

Classification of permanent tissues

1. Simple permanent tissues
2. Complex permanent tissues

Simple Permanent Tissues

A tissue is said to be simple when it is made up of only one type of cells. Here ‘one’ type of cells means that they are structurally and functionally ‘similar to one another. Hence simple permanent tissues are composed of cells which are similar in their structures and coordinate with one another to perform a common function or set of functions.

Parenchyma:

• • The cells have an oval or round shape.
  • The cell wall is made up of hemicellulose or cellulose.
  • The cell is thin-walled.
  • The cells have vacuoles and a very small nucleus.
  • It is found in all parts of the plant.
  • The protoplasm is living and dense.

Collenchyma:

• • Cells are long and thick-walled.
  • The cell wall is made up of cellulose and pectin.
  • It is the only tissue with the highest refractive index due to the presence of pectin.
  • It is found in the epidermis and the vascular bundle of dicot leaf.
  • The amount of chloroplast is less in the cells.
  • The cells have no intercellular spaces.

Sclerenchyma:

• • These are dead tissues, very hard and rigid in texture.
  • Cells are thick-walled with various size and shapes.
  • These provide mechanical support and rigidity to the plant.

Complex Permanent Tissues

The complex tissues are made up of more than one type of cells. These cells differ from one another in their form and structure; however, these cells work together as a unit. Hence, a complex tissue can be defined as a collection of structurally dissimilar cells performing a common function or set of functions.

Xylem:

• • It transports water and nutrients from the roots to the leaves of the plant.
  • It provides support to the plants.
  • It is divided into-tracheids, vessels, xylem fiber, and xylem parenchyma.

Phloem:

• • It translocates the prepared organic food from the leaves to different parts of the plant.
  • It is also known as bast.
  • It is composed of sieve tubes, companion cells, phloem parenchyma, and phloem fibres.