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JAWAHAR NAVODAYA VIDYALAYA
TISSUE NOTES
® Introduction to Tissues
® Plant tissues
Plant tissues are groups of cells that work together to perform specific functions in plants. They are broadly categorized into two main types: meristematic tissues and permanent tissues. Below is an overview of plant tissues and their functions:
1. Meristematic Tissue
¤ Definition : These are undifferentiated cells capable of continuous division and growth.
¤ Location : Found in regions of the plant where growth occurs, such as the tips of roots and shoots (apical meristems), and in the cambium (lateral meristems).
... Types:
• Apical Meristem : Located at the tips of roots and shoots; responsible for primary growth (elongation).
• Lateral Meristem : Found in the cambium; responsible for secondary growth (thickening).
• Intercalary Meristem : Found at the base of leaves or internodes; helps in regrowth after cutting (e.g., in grasses).
2. Permanent Tissue
• Definition : These are differentiated cells that have lost the ability to divide and perform specific functions.
Types :
• Simple Permanent Tissue : Composed of one type of cell.
• Parenchyma : Thin-walled, living cells involved in storage, photosynthesis, and secretion.
• Collenchyma : Thick-walled, living cells providing mechanical support to growing parts.
•Sclerenchyma : Thick-walled, dead cells providing rigidity and strength to mature parts.
• Complex Permanent Tissue : Composed of more than one type of cell.
® Xylem : Conducts water and minerals from roots to other parts; consists of tracheids, vessels, xylem parenchyma, and xylem fibers.
© Phloem : Transports food (sugars) from leaves to other parts; consists of sieve tubes, companion cells, phloem parenchyma, and phloem fibers
3. Epidermal Tissue
Δ : Function : Forms the outer protective layer of the plant.
¤ Features:
• Covered by a waxy cuticle to prevent water loss.
• Contains stomata (tiny pores) for gas exchange.
• May have trichomes (hair-like structures) for protection and reducing water loss.
4. Ground Tissue :
~ Function : Fills the space between epidermal and vascular tissues.
• Types :
¤ Parenchyma : Involved in photosynthesis, storage, and secretion.
¤ Collenchyma : Provides support to growing regions.
¤ Sclerenchyma : Provides strength to mature regions.
5. Vascular Tissue
• Function: Responsible for the transport of water, nutrients, and food.
© Types :
• Xylem: Transports water and minerals upward (unidirectional).
• Phloem : Transports food (sugars) bidirectionally (up and down).
® Key Functions of Plant Tissues:
1. Growth: Meristematic tissues enable primary and secondary growth.
2. Support : Collenchyma and sclerenchyma provide structural support.
3. Transport : Xylem and phloem facilitate the movement of water, nutrients, and food.
4. Protection: Epidermal tissue protects against physical damage, pathogens, and water loss.
5. Storage : Parenchyma stores starch, oils, and water.
6. Photosynthesis : Parenchyma cells in leaves contain chloroplasts for photosynthesis.
• Tissues are groups of similar cells that work together to perform specific functions.
• Tissues are the building blocks of organs and organs are the building blocks of organisms.
• There are four main types of tissues: epithelial, connective, muscle, and nervous tissue.
© Epithelial Tissue:
• Epithelial tissue is a type of tissue that forms the lining of organs and glands.
• It is composed of tightly packed cells that are attached to each other by cell junctions.
• Epithelial tissue is found in the skin, lungs, gut, and other organs.
• Functions of epithelial tissue include:
• Protection: Epithelial tissue protects the underlying tissues from damage and infection.
• Secretion: Epithelial tissue secretes hormones, enzymes, and other substances that help to regulate various bodily functions.
• Absorption: Epithelial tissue helps to absorb nutrients and other substances from the environment.
Δ : Connective Tissue
• Connective tissue is a type of tissue that provides support, structure, and connectivity to the body.
• It is composed of cells and fibers that are embedded in a matrix of ground substance.
• Connective tissue is found in bones, cartilage, tendons, and ligaments.
• Functions of connective tissue include:
• Support: Connective tissue provides support and structure to the body.
• Protection: Connective tissue protects the body from injury and infection.
• Storage: Connective tissue stores fat, water, and other substances that are essential for bodily functions.
Φ Muscle Tissue
• Muscle tissue is a type of tissue that is responsible for movement and contraction.
• It is composed of long, thin cells called muscle fibers that are capable of contracting and relaxing.
•Muscle tissue is found in skeletal muscles, smooth muscles, and cardiac muscles.
• Functions of muscle tissue include:
• Movement: Muscle tissue helps to move the body and its parts.
• Contraction: Muscle tissue contracts to help to pump blood and other fluids through the body.
• Relaxation: Muscle tissue relaxes to help to reduce tension and promote rest.
® Nervous Tissue :
• Nervous tissue is a type of tissue that is responsible for transmitting and processing information.
• It is composed of specialized cells called neurons that are capable of transmitting and receiving signals.
• Nervous tissue is found in the brain, spinal cord, and nerves.
• Functions of nervous tissue include:
• Transmission: Nervous tissue transmits signals from one part of the body to another.
• Processing: Nervous tissue processes information and helps to regulate various bodily functions.
• Control: Nervous tissue helps to control the body's functions, such as movement, sensation, and cognition.
©Types of Tissues
• There are several types of tissues, including:
• Simple epithelial tissue: This type of tissue is composed of a single layer of epithelial cells.
• Stratified epithelial tissue: This type of tissue is composed of multiple layers of epithelial cells.
• Connective tissue: This type of tissue is composed of cells and fibers that are embedded in a matrix of ground substance.
• Muscle tissue: This type of tissue is composed of long, thin cells called muscle fibers that are capable of contracting and relaxing.
• Nervous tissue: This type of tissue is composed of specialized cells called neurons that are capable of transmitting and receiving signals.
I hope these notes help you understand the basics of tissues and their functions! Let me know if you have any questions or need further clarification.