Transport in Plants Lecture Notes

Introduction

• Lecture by Dr. Henna Aseel
• Topic: Transport in plants
• Relevant for IGCSE biology courses

Water Transport in Plants

• Plants absorb water from the soil through roots.
• Water travels up the plant through the xylem to the leaves.
• Xylem: Tubes that transport water and dissolved salts from roots to leaves in one direction.
  • Thick walls containing lignin for structural support.

Photosynthesis

• Leaves take water and carbon dioxide to produce glucose by photosynthesis.
• Glucose is used to produce sucrose and amino acids.

Sugar and Amino Acid Transport

• Phloem: Transports sucrose (sugar) and amino acids up and down the plant.
  • Sucrose is less soluble, minimizing loss.
  • Essential for respiration and protein synthesis in cells.

Structure of Xylem and Phloem

• Position in Root: Xylem in the center, phloem on the sides.
• Position in Stem: Vascular bundles with xylem inside, phloem outside.
• Position in Leaf: Xylem above, phloem below.

Transpiration

• Definition: Loss of water vapor from leaves.
• Occurs by evaporation from mesophyll cells and loss through stomata.
• Leaf Structure:
  • Waxy Cuticle: Prevents excess water loss.
  • Upper Epidermis: Transparent, thin cells.
  • Palisade Mesophyll: Cylindrical cells with chloroplasts.
  • Spongy Mesophyll: Air spaces for gas exchange.
  • Stomata: Openings for gas exchange, surrounded by guard cells.

Experimental Demonstrations

1. To Show Transpiration
   • Cover plant with glass jar and observe water droplet formation.
   • Use anhydrous copper sulfate to test for water.
2. To Show Xylem Function
   • Place stem in colored water to trace water movement.
3. To Show Stomata Function
   • Use cobalt chloride paper to detect water vapor from different sides of a leaf.

Factors Affecting Transpiration

• Temperature: Higher temperature increases transpiration.
• Light Intensity: More light opens stomata, increasing transpiration.
• Air Currents: Wind increases transpiration by maintaining concentration gradient.
• Humidity: High humidity decreases transpiration.

Measuring Transpiration

• Potometer: Measures rate of water uptake, indicating transpiration rate.

Practice Questions

• Questions on water movement, transpiration rate, and plant structure.
• Factors affecting rate of transpiration: temperature, humidity, and light.

Summary

• Understanding transport in plants is crucial for IGCSE biology.
• Key concepts: xylem, phloem, transpiration, and related plant structures.