Xerophytes: Adaptations to Dry Conditions

Introduction

• Xerophytes are plants adapted to survive in extremely dry conditions, such as deserts.
• Common examples include cacti.

Challenges Faced by Xerophytes

• Low Soil Water: Limited availability of water in the soil.
• Low Humidity: Leads to increased water loss.
• High Temperatures: Heightens transpiration rates.

Adaptations of Xerophytes

1. Thick Cuticles

• Function: Reduces transpiration by reducing internal leaf temperature and water evaporation.
• Mechanism:
  • Reflects more light, lowering leaf temperature.
  • Minimizes direct evaporation from leaf surface.

2. Reduced Leaf Surface Area

• Examples: Cactus needles are reduced leaves.
• Benefit: Fewer stomata reduce water vapor loss.

3. Modifying Concentration Gradient

• Concept: Reduce steepness of water vapor concentration gradient between leaf and outside air.

Techniques:

• Trichomes (Leaf Hairs):

  • Trap water vapor, creating a humid micro-environment.
  • Reduces steepness of concentration gradient.

• Sunken Stomata:

  • Increases diffusion distance of water vapor.
  • Maintains moisture near stomata, reducing gradient steepness.

• Rolled Leaves:

  • Form moist environments within rolled structure.
  • Helps in reducing gradient steepness by maintaining moisture.

Conclusion

• Xerophytes utilize various adaptations to manage water loss and survive in arid environments.
• These adaptations help create localized humid conditions despite the dry external environment, effectively reducing the rate of transpiration.