Xerophytes and Their Adaptations

Overview

• Xerophytes: Plants that live in very dry, arid areas
• Water loss is a significant challenge
• Xerophytes have adaptations to reduce water loss

Water Potential

• Water moves down the water potential gradient (high to low)
• High water potential: Inside cells of xerophytes
• Low water potential: Air (due to low humidity in dry areas)
• Reducing the steepness of water potential gradient helps in reducing water loss
• The steeper the gradient, the faster the water is lost

Adaptations

Rolled Leaves and Hairs

• Example: Marum grass
• Features of rolled leaves:
  • Rolled leaves instead of flat leaves
  • Stomata on the upper epidermis
  • Presence of hairs on the upper epidermis
• Benefits:
  • Air trapped inside rolled leaves increases humidity
  • Higher humidity reduces water potential gradient
  • Less water is lost as water potential gradient decreases

Sunken Stomata

• Stomata are located in pits (sunken)
• Features of Sunken Stomata:
  • Stomata are below the leaf surface
  • High humidity is trapped in the sunken area
• Benefits:
  • Trapped humid air decreases water potential gradient
  • Reduces the rate of water loss

Comparison with Non-Xerophytic Cells

• Non-xerophytic cells have stomata exposed directly to outside air
• Higher water potential gradient in non-xerophytic cells due to lack of trapped humid air
• More water is lost in non-xerophytic plants compared to xerophytes

Other Adaptations (Overview)

• Multiple other adaptations exist, but not all detailed in the lecture
• Review additional adaptations independently

Summary

• Xerophytes have specialized adaptations to survive in dry environments
• Primary goal: Reduce water loss by minimizing water potential gradient

Key Terms

• Xerophytes: Plants in dry areas
• Water Potential Gradient: Movement of water from high to low potential
• Stomata: Pores on leaf surfaces for gas exchange
• Rolled Leaves: Leaves rolled to trap humidity
• Sunken Stomata: Stomata located in pits to retain humidity