| Types of Permanent Tissues |
- Epidermal tissues layer is at the outermost surface of stems, leaves and roots of young plants.
- Epidermal cell walls which are exposed to the air have a waxy and waterproof layer called the cuticle.
- The cuticle reduces loss of water through evaporation (transpiration) and protects the leaf from mechanical injuries and pathogens.
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- Parenchyma tissues:
- Paracenchyma tissues are the simplest living cells and do not undergo differentiation.
- They have the thinnest cell walls.
- Parenchyma tissues are always in a turgid state providing support and maintaining the shape of herbaceous plants.
- Involved in photosynthesis, helping in the storage of starch and sugar and involved in gaseous exchange.
- Involved in the repair and regeneration of plant tissue as well as in the vascular system.
- Collenchyma tissues:
- Collenchyma tissues are made of living cells which mature into cells that are flexible.
- Have cell walls made of pectin and hemicellulose.
- Their cell walls are thicker than parenchyma tissues.
- Provide mechanical support and elasticity to plants.
- Sclerenchyma tissues:
- Sclerenchyma tissues consist of dead cells when they are matured.
- Their cell walls are the thickest among the three ground tissues.
- Provide support and mechanical strength to the parts of matured plants.
- These tissues also help in the transport of water and nutrients in plants.
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- Xylem:
- The xylem is made up of dead cells without cytoplasm.
- The cell wall of the xylem contains lignin.
- Consists of xylem vessels that are elongated, hollow and connected from its roots to the leaves.
- This enables xylem to transport water and mineral salt to all parts of a plant.
- Phloem:
- Phloems are made of companion cells and sieve tubes.
- Made of living cells, which are the sieve tubes with the presence of cytoplasm.
- The sieve tubes do not have organelles such as nucleus and ribosome as they decompose at the maturity stage.
- Phloems consist of sieve tubes arranged from end to end forming elongated and continuous tube structures.
- Phloems transport sugars produced from the photosynthesis from the leaves to storage organs such as roots, fruits and tubers.
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