Cells are the fundamental unit of life. When a group of cells teams up to perform a specialized function, the group of cells is called a ‘Tissue’. All cells in a tissue are of similar shape and size, and work in tandem to accomplish their designated function.
Just as animals and human beings have tissues that perform specific functions, plants too have tissues that work towards accomplishing specific life activities in the plant.
Plant tissues can be divided into the following two types-
- Meristematic Tissues
- Permanent Tissues
Meristematic tissues contribute towards the growth of the plant. They are formative tissues which generate and add new cells to the plant body. Their efforts lead to the growth of the plant, in both length and width.
Since they contribute towards growth, meristematic tissues are found in the regions where growth of the plant takes place- namely, the tip of the root and the tip of the stem. Meristematic tissues are also present laterally in the plant body, which contribute in the growth of the thickness of the plant. These tissues also give rise to permanent tissues.
Meristematic tissues display the following distinguishing features-
- They are composed of small-sized cells.
- The walls of the cells are thin.
- The cells are tightly packed together, with no intercellular spaces between them.
- The cells divide prolifically, thus bringing about growth.
- The cells are rich in cytoplasm and have large, conspicuous nuclei.
Permanent tissues are concerned with the important functions of absorption of nutrients, conduction of those nutrients and protection of various parts of the plants. They, therefore, form the bulk of the plant body.
Permanent tissues display the following distinguishing features-
- The cells are large and thick-walled.
- The cells do not contain much cytoplasm, and have smaller nuclei.
- The cells do not divide.
Permanent tissues can be divided into different types of tissues in the following two ways-
- Based on their location or origin-
- Dermal Tissue- this tissue is present on the outermost layer of the plant, on the surface of the leaves, roots, stem, flowers and fruits. It is commonly called the epidermis. Its functions are as follows-
- It is a protective tissue. It protects the parts of the plant.
- Dermal tissue in the roots helps in the absorption of water and nutrients from the soil.
- Dermal tissue in the leaves helps in reducing loss of water through transpiration. To achieve this, cells of the tissue are thick-walled in structure. It also helps in the exchange of oxygen and carbon dioxide between the plant and atmosphere, through tiny pores called stomata.
- Vascular Tissue- This tissue is primarily concerned with the transport of food, nutrients and water throughout the body of the plant. It is therefore, also known as conducting tissue. It is of two types- Xylem and Phloem. Its functions are as follows-
- Xylem transports water and minerals from roots to leaves and to other plant parts, while phloem transports the food synthesised by the leaves to all the other parts of the plant.
- Vascular tissue provides mechanical support to the plant stem and leaves.
- Ground Tissue- This tissue is also called supporting tissue because it provides support to the plant parts. It is found in leaves, stem, roots, flowers and fruits.
- Based on the type of cells-
- Simple Tissues- These tissues are made up of a single type of cell. They are of three types- parenchyma, collenchyma and sclerenchyma. Out of these three, the first two consist of living cells, while sclerenchyma is composed of thick-walled, dead cells. The functions of simple tissues are as follows-
- Parenchyma stores food, e.g. in potato. In leaves, its cells contain chlorophyll. It thus helps in photosynthesis.
- Collenchyma is present in growing stems and leaves, and provides mechanical support to the plants.
- Sclerenchyma is found in the hard parts of the plant body, such as the bark. It provides strength to the plant body.
- Complex Tissues- These tissues are made up of more than one type of cells. They are of two types- Xylem and Phloem. These tissues are concerned with the transport of materials within the plant body.