A permanent tissue whose cells have different size, shape and structural characteristics is called complex tissue. Complex tissue is divided into two parts. Xylem and phloem.
1. Zylem: Greek word Xylon means wood. The tissue that transports water and mineral salts from the root of the plant to different parts of the body is called xylem. It consists of four components. Trachyds, trachea or vessels, xylem fibers and xylem parenchyma. Among them xylem parenchyma is the only living material. Xylem fibers are called wood fibers. Coconut fiber or coir is a type of wood fiber. Ferns and gymnosperms do not have vessels. Besides, the plants of Winteraceae, Tetracentraceae, Trochodendraceae etc. do not have vessels. Different types of xylem are-
(i) Protoxylem: Vessel cells with narrow pores are called protoxylem.
(ii) Metaxylem: Vessel cells with large pores are called metaxylem.
(iii) Exarc: If protoxylem is towards the periphery and metaxylem towards the centre, it is called exarc. Root xylem is exarc in nature.
(iv) Endarc: If protoxylem is towards the center and metaxylem towards the periphery, it is called endarc. The xylem of stem is endarc in nature.
(v) Mesarc : When protoxylem and metaxylem are arranged on both sides, it is called mesarc. Mesarc xylem is found in the leaves of ferns and cycads.
(vi) Centrach : When protoxylem is in the center and metaxylem is located around it, it is called centrach. Centarch xylem is found in fern plants.

Functions of Xylem
(i) Transports water and mineral salts in the plant body.
(ii) Stores water and mineral salts in the plant body.
(iii) It imparts vigor to plants.
(iv) Provides mechanical energy to plants.
(v) Assists in photosynthesis of plants.
(vi) Helps plants in respiration.
(vii) Aids diffusion and osmosis in the plant body.
(viii) It forms wood in the plant body.
(ix) It participates in the formation of the main structure of the plant body.

2. Phloem : Greek word Phloos mean bark. It transports food from plant leaves to different parts of the body. It consists of four components. Synovial, companion cells, phloem parenchyma and phloem fibers. The resulting sivnol or sivcell does not have a nucleus. The fibers present in the secondary phloem are called bast fibers. Jute fibers are bast fibers.

Functions of Phloem
(i) Phloem transports food in the plant body.
(ii) Stores food in the plant body.
(iii) Assists in photosynthesis of plants.
(iv) It imparts vigor to plants.
(v) Provides mechanical energy to plants.
(vi) It forms fibers in the plant body.

(i) Provides mechanical advantage to plants.
(ii) Protects the plant from various environmental stresses and strains.
(iii) Contains waste material in the dead state.
(iv) Protects soft parts of fruits and seeds.
(v) Transports little water.

Sclerenchyma consists of lignin-rich, thick-walled cells. The transformed cells are dead and do not contain protoplasm. There are no intercellular spaces. Cells are tough and elastic. Cells are longer than wide.

(i) Collenchyma containing chloroplasts (chlorenchyma) produces food.
(ii) Provides mechanical strength to growing and soft organs of plants.
(iii) Helps plants to bend due to elastic and extensible properties.
(iv) Plant organs do not break easily as they are elastic.

Collenchyma consists of living cells without lignin, having thick walls. Cells are multilobed or elongated. There are no intercellular spaces. Cells are proliferative.

(i) Chlorophyll-containing parenchyma (chlorenchyma) produces food in the process of photosynthesis.
(ii) Parenchyma of aquatic plants holds air deposits (arenchyma) and helps the plant to float.
(iii) Lower stems, roots, fruits and seeds contain sugars, proteins and carbohydrates.
(iv) Helps in plant wound healing and regeneration.
(v) Provides strength to leaves and stems.
(vi) Stamens keep the plant upright by hydrostatic pressure.
(vii) Propagation by asexual roots and shoots.
(viii) Tissues containing xylem and phloem transport water and mineral salts.

The length, width and depth of the tissue cells are almost the same is called parenchyma. Cells are concentric and round, ovoid, multilobed or oblong. Intercellular spaces exist. Parenchyma tissue consists of stem and root skin, cortex, pith, medulla, pericycle, leaf mesophyll, fruit shell, seed and embryo.

Permanent tissue is divided into three parts. Simple tissue, complex tissue and secretory tissue.
Simple tissue
A permanent tissue whose cells have the same size, shape and structure is called simple tissue. Simple tissue is divided into three parts. These are-
1. Parenchyma: The length, width and depth of the tissue cells are almost the same is called parenchyma. Cells are concentric and round, ovoid, multilobed or oblong. Intercellular spaces exist. Parenchyma tissue consists of stem and root skin, cortex, pith, medulla, pericycle, leaf mesophyll, fruit shell, seed and embryo.

Functions of parenchyma tissue
(i) Chlorophyll-containing parenchyma (chlorenchyma) produces food in the process of photosynthesis.
(ii) Parenchyma of aquatic plants holds air deposits (arenchyma) and helps the plant to float.
(iii) Lower stems, roots, fruits and seeds contain sugars, proteins and carbohydrates.
(iv) Helps in plant wound healing and regeneration.
(v) Provides strength to leaves and stems.
(vi) Stamens keep the plant upright by hydrostatic pressure.
(vii) Propagation by asexual roots and shoots.
(viii) Tissues containing xylem and phloem transport water and mineral salts.
2. Collenchyma: Collenchyma consists of living cells without lignin, having thick walls. Cells are multilobed or elongated. There are no intercellular spaces. Cells are proliferative.
Functions of collenchyma tissue
(i) Collenchyma containing chloroplasts (chlorenchyma) produces food.
(ii) Provides mechanical strength to growing and soft organs of plants.
(iii) Helps plants to bend due to elastic and extensible properties.
(iv) Plant organs do not break easily as they are elastic.
3. Sclerenchyma: Sclerenchyma consists of lignin-rich, thick-walled cells. The transformed cells are dead and do not contain protoplasm. There are no intercellular spaces. Cells are tough and elastic. Cells are longer than wide.
Functions of Sclerenchyma Tissue
(i) Provides mechanical advantage to plants.
(ii) Protects the plant from various environmental stresses and strains.
(iii) Contains waste material in the dead state.
(iv) Protects soft parts of fruits and seeds.
(v) Transports little water.

1. The cells are non-dividing and reside in the stationary zone of the plant.
2. The cytoplasm of the cell is thin.
3. Cell nucleus is relatively small.
4. Cells are living or dead and asymmetric.
5. Cells are irregular in shape.
6. Their cells have cell cavities.
7. They have intercellular spaces.
8. Cells have a low metabolic rate.
9. Various designs are seen in cells.
10. Their cell walls are thick and made of lignin and pectin.

A tissue whose cells are unable to divide is called permanent tissue. Divisive tissue becomes permanent tissue when its ability to divide is suspended. For example- xylem, phloem etc.