Permanent tissues:

Permanent tissues originate from the meristematic tissues. These tissues are composed of cells, which cannot divide.

Types of Permanent Tissues:

They are further classified into the following types:

1. Epidermal Tissues:

Epidermal tissues are composed of a single layer of cells and they cover the plant body. They act as a barrier between the environment and the internal plant tissues.

Functions of Epidermal tissues:

They are also responsible for the absorption of water and minerals primarily in the root region. On stem and leaves, they secrete Cutin (the coating of cutin is called the cuticle) which prevents evaporation.

Epidermal tissues also have some specialized cells that perform specific functions.

For Example:

Root hairs:

Root hairs absorb water and minerals.

Leaf hairs:

Leaf hairs (1-2 cells) reflect light to protect against overheating and excessive water loss. The layer of leaf hairs acts to hold in a layer of humidity “trapped”. This layer also prevents air from moving directly against the stomata which would encourage water loss.

Stomata:

Stomata are made by guard cells and are most abundant on the underside of leaves. They regulate the diffusion of CO₂ into the leaf for photosynthesis as well as regulate the loss of water from the leaf.

Salt Glands:

Salt glands are the waste bins for the excess salts absorbed from the soil. They form a crust of salt in leaves which reflects light to prevent overheating.

1. Ground Tissues:

Ground tissues are simple tissues made up of parenchyma cells. Parenchyma cells are the most abundant cells in plants.

The function of ground tissues:

Overall they are spherical but flat at the point of contact. They have thin primary cell walls and large vacuoles for the storage of food. In leaves, are cold mesophyll and are the sites of photosynthesis. In other parts, they are the sites of respiration and protein synthesis.

1. Support tissues:

These tissues provide strength and flexibility to the plants.

Types of support tissues:

They are further of two types:

1. Collenchyma tissue:

They are found just beneath the epidermis in the cortex of young herbaceous stems and the midribs of leaves and petals of flowers, they are made of elongated cells with evenly thickened primary cell walls. They are flexible and function to support the organs in which they are found.

1. Sclerenchyma tissue:

They are composed of cells with rigid secondary cell walls. The cell walls are hardened with lines in lignin, which is the main chemical component of wood. Mature sclerenchyma cells cannot elongate and most of them are dead.

Types of Sclerenchyma tissue:

There are two types of cells in Sclerenchyma tissues:

• Fiber cells:

Fiber cells are associated with phloem and xylem tissues.

• Sclerite cells:

Sclerite cells are found in seed coats.

Compound (complex) tissues:

A plant tissue composed of more than one type of cell is called a compound or complex tissue. Xylem and phloem tissues found only in vascular plants are examples of compound tissues.