Adaptations of Xerophytes and Hydrophytes

Xerophytes

1. Rolled Leaves

   • Example: Marram grass on Sand Dunes.
   • Purpose: Reduce surface area for evaporation of water vapor.
   • Traps a layer of water vapor close to stomata, creating a high water vapor potential outside stomata, reducing water vapor potential gradient, and thereby reducing evaporation.

2. Hairy Leaves

   • Purpose: Same as rolled leaves.
   • Traps a layer of water vapor; reduces water vapor potential gradient.

3. Sunken Stomata

   • Stomata situated in pits.
   • Traps water vapor, creating a high water vapor potential outside stomata, reducing evaporation.

4. Needle-like Leaves

   • Example: Pine trees in cold environments.
   • Purpose: Reduce surface area for evaporation of water.

5. Dense Spongy Mesophyll

   • Smaller area for evaporation from vascular bundle inside leaf to spongy mesophyll, reducing overall evaporation.

6. Other Adaptations

   • Fewer stomata, closed during the day.
   • Stomata found on the lower surface of leaves.
   • Thick, waxy cuticle to prevent water loss.
   • Long, deep roots to access water with high solute concentration, aiding in water uptake via osmosis.

Hydrophytes

1. Erenchyma

   • Plant tissue with air spaces, providing buoyancy.

2. Large Leaves

   • Increases rate of photosynthesis.
   • Water is not a limiting factor.

3. Pneumatophores

   • Specialized roots for gas exchange, enhancing photosynthesis.
   • Roots grow out of the water.

4. Other Adaptations

   • Plenty of stomata, open most of the time.
   • Stomata on the upper surface of leaves.
   • Thinner waxy cuticle.
   • Short root system to avoid damage from currents and because water is readily available.

Key Reminders

• Use the term "water vapor" instead of just "water."
• Use scientific terminology in exams.