BL1004- stomata

Stomata Background Information

Stomata are microscopic pores found on plant leaves and some stems, surrounded by specialized guard cells. They play crucial roles in gas exchange and water regulation.

• Structure and Distribution
  Found on upper and/or lower leaf surfaces

• Guard cells are kidney-shaped in dicots and dumbbell-shaped in monocots

+: • Facilitate CO2 and 02 exchange for photosynthesis

• Control water loss through transpiration

• Stomatal Opening and Closing Mechanism
  Guard cells regulate stomatal aperture through changes in turgor pressure, influenced by:

• Potassium ion (K+) pumps

• Abscisic acid hormone

• Environmental cues

• Environmental Factors Affecting Stomata

• Light: Stimulates opening during the day

• CO2 concentration: Low internal levels promote opening

• Water availability: Deficiency causes closure

• Temperature and humidity: High temperatures and low humidity promote closure

• Photosynthetic Adaptations
  To optimise carbon fixation and water conservation:

• C3 plants: Most common, fix carbon directly via Rubisco in cool, wet environments

• C4 plants: Spatially separate carbon fixation, adapted to hot, dry environments

• CAM plants: Temporally separate carbon fixation, suited for very dry/arid environments

  nail polish impression technique.

  • Materials

  • Ivy leaf (C3 plant)

  • Aloe vera leaf section (CAM plant)

  • Clear nail polish

  • Clear tape

  • Microscope slides

  • Razor blade

  • Microscope (capable of 400x magnification)

  v Procedure

  1. Identify the lower leaf surface of each plant.

  2. Apply a thin, even layer of nail polish over a 2cm x 2cm section on the lower surface of each leaf.

  3. Allow the nail polish to dry completely (approximately 10 minutes).

  4. Place clear tape over the dried nail polish and press firmly.

  5. Carefully peel off the tape with the nail polish impression.

  6. Stick the tape (sticky side down) onto a labeled microscope slide. Trim excess tape with a razor blade.

  7. View the impressions under a microscope at 400x magnification.

  8. Count the number of stomata in three different areas for each leaf sample.

  9. Calculate the average stomatal density for each leaf type.

  10. Submit your data to your demonstrator for compilation and analysis.

  Remember to set consistent counting rules (e.g., only count whole stomata visible within the field of view) and ensure proper identification of stomata versus epidermal cells.