Chapter 25 focuses on plant tissues with emphasis on the leaf and root structure and their functions.
Leaves
Leaf Structure and Function
Leaves are specifically adapted to optimize photosynthesis activity. Their structure allows efficient sunlight absorption.
Anatomy of a Leaf
Blade: Thin, flattened part to maximize light absorption.
Petiole: The thin stalk that connects the blade to the stem.
Dermal Tissue: An outer covering that protects the leaf, made primarily of epidermal cells.
Ground Tissue: Innermost tissue containing layers like palisade and spongy mesophyll.
Vascular Tissue: Includes xylem and phloem, arranged in bundles or leaf veins, transporting water, nutrients, and sugars.
Dermal Tissue
Epidermis: Upper and lower surfaces of the leaf are covered by this protective layer.
Cuticle: A waxy layer on the epidermis that reduces water loss through evaporation.
Vascular Tissue
Xylem and Phloem: These tissues work together in the leaf veins to facilitate the transport of essential substances.
Mesophyll
Palisade Mesophyll: Layer under the upper epidermis composed of tightly packed cells; primary site of photosynthesis due to high light absorption.
Spongy Mesophyll: Layer beneath the palisade with air spaces that allow gas exchange.
Stomata
Stomata: Small openings in the epidermis enabling gas exchange (carbon dioxide, water vapor, oxygen) essential for photosynthesis.
Roots
Types of Root Systems
Taproot Systems: Characteristic of dicots, featuring a thick primary root with smaller branches (e.g., carrots).
Fibrous Root Systems: Characteristic of monocots, such as grasses, with many thin, equal-sized roots emerging from the stem base. Help prevent soil erosion.
Anatomy of a Root
Epidermis: Protective outer layer, crucial for absorption. Contains root hairs that increase surface area for water/mineral absorption.
Cortex: Region of ground tissue that supports and transports water/minerals from the epidermis.
Vascular Cylinder: Central area comprising xylem and phloem, involved in transporting water and nutrients throughout the plant.
Endodermis: Inner layer that regulates the movement of materials into the vascular cylinder.
Apical Meristem: Area at root tips where growth occurs, protected by a root cap to ease penetration through soil.
Key Terms
Xylem: Tissue that carries water and minerals from the roots to the rest of the plant.
Phloem: Tissue that transports sugars produced during photosynthesis.
Meristem: Tissue responsible for growth, dividing to create new cells.
Root Hairs: Extensions of epidermal cells that increase absorption capacity.