Stem and Leaf Lecture
Page 1: Plant Structure: Stems and Roots
Overview of plant structure with a focus on stems and roots.
Page 2: Concept of the Plant Body
Definition of the plant body, primarily consisting of the stem and its attached parts.
Page 3: Key Components
Shoot Tip (Apical Bud): Growth point of the stem.
Terminal Bud: The end bud that grows vertically.
Lateral Bud (Axillary Bud): Buds that form in the leaf axils, allowing lateral growth.
Node: Points on the stem where stems or leaves arise.
Internode: The segments of the stem between the nodes.
Vascular Tissues: Comprising xylem and phloem, responsible for transporting materials.
Ground Tissue: Fills the plant space, involved in photosynthesis and storage.
Roots: Key function in nutrient uptake and stability of the plant.
Page 4: Structure of the Stem
Nodes: Areas on the stem with attached parts such as leaves and buds.
Leaves
Axillary Buds
Stipules
Internodes: Areas between nodes without attachments, allowing elongation.
Page 5: Types of Buds
Terminal Bud: Also referred to as the apical bud, located at the top of the stem.
Axillary Bud: Also known as a lateral bud, found in the leaf axil.
Additional structures: Node and petiole (base of the leaf).
Internode: Section of stem between two nodes.
Page 6: Observation of a Twig
Example: Hickory tree twig in winter, without leaves.
Features to note: terminal bud, axillary bud, leaf scars, nodes, and internodes.
Description of “knuckle” nodes.
Page 7: Function of Buds
Buds are embryonic stems that develop new leaves and stems.
New growth originates from these buds as the plant expands.
Page 8: Meristematic Tissue
Meristem: The microscopic growing point in the bud, consisting of a few cells.
Critical role in cell division and new growth cycles.
Page 9: Structure of Buds
Each bud contains at least one meristem, essential for plant growth.
Page 10: Growth Dynamics
New growth arises from the tips of stems and roots.
Concept of growth illustrated by the analogy of carved initials; the plant expands wider, rather than taller.
Page 11: Internal Stem Anatomy
Examination of the structure of stems at a cellular level.
Page 12: Vascular Tissue
Xylem: Pronounced as ZIE-lum. Key for upward transport.
Phloem: Pronounced as FLOW-um. Involved in downward and lateral transport.
Page 13: Functions of Xylem
Xylem is non-living when functional, primarily responsible for the upward movement of water and minerals from roots to leaves.
Composed of vessels or tracheids.
Page 14: Understanding Directional Flow
UP: Movement of water from roots through the stems to leaves, not solely against gravity.
DOWN: Movement of sugars and metabolites from leaves to roots.
Page 15: Functions of Phloem
Phloem remains alive when functional; it transports sugars, hormones, and other metabolites.
Movement follows a 'source-to-sink' pattern, which can be upwards or downwards.
Page 16: Summary of Vascular Functions
Xylem: Dead at functionality; carries water and nutrients up; consists of vessels and tracheids.
Phloem: Alive at functionality; carries metabolic products; follows source-to-sink movement.
Page 17: Cross-Section of Herbaceous Stem
Identifies layers showing the arrangement of vascular tissues in a typical herbaceous stem.
Page 18: Cross-Section of Developing Wood Stem
Compares cross-section of stem beginning to develop wood, detailing vascular bundles and cambium.
Page 19: Structure of Woody Stems
Description of wood as a solid xylem cylinder, with the inner bark being phloem.
Page 20: Vascular Cambium
Defined as a type of meristem that contributes to the thickening of stems in woody plants.
Composed of a single cell layer, situated between xylem and phloem.
Page 21: Types of Meristems
Primary Meristems: Found in buds and root tips, responsible for new organ formation.
Secondary Meristems: Like vascular cambium, responsible for increasing thickness of existing organs.
Page 22: Characteristics of Roots
Roots lack nodes but have xylem and phloem.
Can be either herbaceous or woody, generally found underground, often lacking attached parts.
Page 23: Typical Herbaceous Root Structure
Phloem: Present in root structure.
Xylem: Facilitates upward water transport.
Pericycle: A layer filtering unwanted materials.
Page 24: Reiteration of Key Components
Highlighting key structures such as shoot tip, vascular tissues, roots, and associated functions.
Page 25: Internal Leaf Anatomy
Cross-sectional examination of a Privet leaf to study its structure.
Page 26: Continued Cross-Section of the Leaf
Further detailing leaf anatomy with emphasis on different tissue layers.
Page 27: Cuticle Layer
Cuticle: The outer protective layer of leaves, aids in moisture retention.
Page 28: Upper Epidermis
Composed of epidermal cells; serves as a protective layer above the leaf.
Cuticle present for protection.
Page 29: Palisade Mesophyll
Palisade Mesophyll: Layer of chlorophyll-rich cells, essential for photosynthesis.
Positioned under the upper epidermis.
Page 30: Chloroplast Functionality
Presence of chloroplasts in the palisade mesophyll, highlighting their role in photosynthesis.
Page 31: Spongy Mesophyll
Spongy Mesophyll: Layer of cells below palisade; aids in gas exchange, with spaces for gas movement.
Page 32: Additional Chloroplast Presence
More chloroplasts noted within the mesophyll layers, emphasizing photosynthesis.
Page 33: Lower Epidermis
Structure and function of the lower epidermis with key roles in protection and gas exchange.
Page 34: Lower Surface Details
Continued details on structure, including cuticle and chloroplasts presence.
Page 35: Vascular Bundle Structure
Overview of vascular bundles in the leaf providing transportation of water and nutrients.
Page 36: Stomata Functionality
Explanation of the function of stomata and their regulation by guard cells for gas exchange.
Page 37: Interaction of Air with Mesophyll
Description of air spaces in the spongy mesophyll facilitating gas exchange.
Page 38: Lower Leaf Surface Functionality
Guard Cells: Regulate the opening and closing of stomata on the leaf surface.
Page 39: Final Overview of Lower Leaf Surface
Summary of the structures and their functions in the lower leaf surface.
Page 40: Guard Cell Structure
Detailed view of guard cells associated with stomatal openings, aiding in gas exchange.