Plants perform several life processes like growth, respiration, excretion, photosynthesis.
Plant cell has a cell wall. The group of cells that perform a similar function and are similar in structure is known as tissue.
There are basically four types of tissues in plants
- MERISTEMATIC TISSUES
- DERMAL TISSUES
- GROUND TISSUES
- VASCULAR TISSUES
- Tissues that brings about overall growth and repair in a plant is the meristematic tissue.
- It brings about the growth in the plant body.
- This tissue is again classified into three types
- Apical Meristematic tissue
- Lateral Meristematic tissue
- Intercalary Meristematic tissue.
APICAL MERISTEMATIC TISSUE
- The tissues that helps in the growth of the plant is called Apical Meristematic.
- This tissue is present at the growing tips, sides and in between layers of other tissues.
- E.g., root tip, shoot tip
LATERAL MERISTEMATIC TISSUE
- Tissue that gives rise to the growth in girth of the steam is called Lateral Meristematic.
- This tissue is present at the edges in a lateral manner.
INTERCALARY MERISTEMATIC TISSUE
- Tissue that present at the branching takes place or a leaf or a flower stalk grows are known as intercalary Meristematic.
- Dermal tissue is usually consisting of a single layer of tissue showing variation in the types of cells
- The tissue that protects the plants from water loss, mechanical damage and invasion by disease causing organisms is the dermal tissue.
- It secrets various excretory products.
- On the basis of their location and function dermal tissues are studied as three different types.
- Epidermis (outermost layer)
- Mesodermis (middle layer)
- Endodermis (innermost layer)
- The wall of the cells of dermal tissue are thicker as compared to the cells of Meristematic tissues.
- In desert plants it may be even more thick and waxy. Small pores are seen in the epidermis of the leaf, called stomata.
- They are enclosed by two kidney shaped cells, called guard cells.
- Cells of the roots have long hair like parts, called root hair.
FUNCTION OF DERMAL TISSUE
- Stomata and root hair also dermal tissues that are essential for gaseous exchange and transpiration as well as absorption of water and minerals respectively.
- In big trees the dermal tissues from several layers above the epidermis it is called bark.
- Tissues that forms the bulk of the plant body is called ground tissue. It helps in storing food and give physical support to the plant.
- There are mainly three types of ground tissues. They are
- The cell of the Parenchyma is soft, thin walled and loosely packed.
- Parenchyma again classified as three types
- STORAGE TISSUE
- The Parenchyma which contains a chloroplast is known as Chlorenchyma.
- They perform photosynthesis.
- E.g., Palisade Parenchyma, spongy Parenchyma.
- The Parenchyma which contains large air cavities or space is called Aerenchyma.
- They provide buoyancy.
- E.g., Cortex of water plants like Hydrilla, Eichornia.
- The Parenchyma which stores water, food or waste materials is called Storage Tissue.
- The help in storage of reserve food.
- E.g., Endodermis of seeds.
- Collenchyma tissues have thicker walled, longer cells compared to Parenchyma.
- This gives mechanical support to plant.
- Intercellular space is present.
- In the Sclerenchyma the cells are thick walled and compactly arranged with nearly no space between them.
- They give mechanical strength to the plant.
- Any tissues which contain vessels through which fluids are passed is called a Vascular tissue.
- Vascular tissue gives mechanical support to the plant as well.
- The Vascular tissues are again classified as two types
- Xylem conducts water and material salt from the roots to the leaves.
- Tracheid, vessels, fibers and Parenchyma are consists of Xylem
- In Xylem only Xylem parenchyma is living.
- Phloem conducts food from the leaves to the growing parts of the plants.
- The Phloem consists of sieve cells, sieve tubes, companion cells, fibers and Parenchyma.
- Only phloem fibers are non-living.