BSC2011 Exam 2- Vertebrate table
Page 1: Introduction to Plant Water and Nutrition
Plants obtain nutrients and water through specialized systems.
Page 2: Learning Objectives
Explain the structure of a typical plant vascular system:
Vascular tissues include xylem and phloem.
Define the apoplastic and symplastic routes for water movement in plants.
Describe the transpiration-cohesion-tension model governing water flow.
Clarify if transpiration requires energy.
Explain the pressure flow model for phloem movement.
Page 3: Vascular Tissue Overview
Vascular tissue functions as a network for:
Conducting water and minerals: Xylem
Conducting sugars: Phloem
Page 4: Structure of Vascular Plants
Components of vascular plants:
Vascular tissue: Xylem (transports water) + Phloem (transports sugars)
Key structures: Leaves, Stem, Roots
Page 5: Xylem Cells
Types of xylem cells:
Tracheids: Found in all vascular plants; evolved first.
Vessels: Present in flowering plants.
Functional xylem tissue consists solely of cell walls as functional cells are dead.
Page 6: Leaf Anatomy
Water and minerals enter leaves through the xylem.
Sugars exit leaves through the phloem.
Key components of leaf cells:
Central vacuole, nucleus, chloroplast, mitochondrion.
Stoma allow for gas exchange (O₂ exits, CO₂ enters).
Page 7: Water Transport in Tall Trees
Water Requirements: Tall trees must transport ~100 gal/day for photosynthesis and cellular integrity.
Mechanism to lift water involves physical principles and energy considerations.
Page 8: Efficient Water Movement
Trees may need to lift ~400 liters/day to great heights (up to 100m).
Energy equivalent calculated as 118,000 Joules (~28 kcal).
Page 9: Root Structure
Root Hairs: Main site of water absorption.
Other components include:
Root cap, mucigel sheath, emerging lateral root.
Area of absorption concentrated around root hairs.
Page 10: Water Movement Pathways
Apoplast Route: Utilizes cell walls and intercellular spaces; does not cross cell membranes.
Symplast Route: Involves movement through living cells connected by plasmodesmata.
Page 11: Cell Structure in Water Transport
Components involved in water transport:
Cell membrane, cytoplasm, plasmodesmata, and cell wall.
Page 12: Root Cell Layers
Layers of root (from outside to inside):
Epidermis, cortex, endodermis, pericycle, and vascular tissue (xylem and phloem).
Page 13: Vascular Tissue Structure
Vascular Cylinder: Composed of xylem and phloem in plant roots and stems.
Structure runs throughout the plant, connecting various parts.
Page 14: Leaf Anatomy Revisited
Overview of components aiding in water and sugar transport:
Trichomes, central vacuole, nucleus, chloroplast, leaf veins, and epidermal cell types.
Page 15: Role of Stomata
Stomata as key structures for hydration:
Allow for gas exchange and transpiration.
Page 16: Functions of Stomata
Open Stomata: CO₂ enters, O₂ leaves, and water evaporates.
Closed Stomata: Prevents water loss but limits CO₂ intake and traps O₂.
Page 17: Stoma Mechanics
Demonstration of guard cells controlling stoma state:
Open: Allows gas exchange.
Closed: Conserves water.
Page 18: Stomata and Water Transport
Stomata control xylem water flow:
Opening allows CO₂ uptake and promotes transpiration.
Closing conserves water during dry conditions.
Page 19: Cohesion and Adhesion Mechanisms
Cohesion: Attraction between water molecules (hydrogen bonding).
Adhesion: Attraction between water and other materials.
Page 20: Surface Tension and Capillary Action
Cohesion and adhesion lead to surface tension and capillary effects;
Water meniscus formation in tubes.
Page 21: Capillary Action in Plants
Capillary action demonstrates how water is raised in xylem cells due to adhesion and cohesion forces.
Page 22: Mechanisms of Water Transport
Cohesion keeps water molecules in a column, allowing for effective transport in xylem cells.
Page 23: Transpiration-Cohesion-Tension Mechanism
Overview of water movement from roots to leaves through transpiration:
Leaf, vein, mesophyll cells participate in this process.
Page 24: Xylem Transport
Visual representation of xylem's water transport mechanisms within plants.
Page 25: Transpiration-Cohesion-Tension Summary
Evaporation drives the transpiration-cohesion-tension mechanism.
Tension resulting from water loss increases flow along the plant.
Page 26: Energy Efficiency in Water Transport
Plants utilize evaporation to aid water movement, requiring no ATP for active transport.
Water movement efficiency varies with environmental conditions like temperature.
Page 27: Additional Resources
Reference to a video that further explains the transpiration/cohesion/tension mechanism in plants.
Page 28: Anatomy of Phloem
Phloem sap comprises sucrose, amino acids, etc.
Flow rates can be high (~0.5m/h). Different sieve tubes transport in various directions.
Page 29: The Pressure Flow Model
Active and passive transport mechanisms govern phloem movement; active transport of sugars requires energy.
Page 30: Solute Transport in Phloem
Pressure Flow Model: Sucrose moves into companion cells via active transport, diffuses into sieve tubes, increasing pressure; driving sap flow to sinks where it's utilized or stored.