Adaptive Features - 2 | Biology for GCSE/IGCSE - Year 11 PDF Download

Hydrophytes

• Plants adapted to thrive in extremely wet conditions
• Adaptations of Hydrophytes:
  • Large air spaces present in their leaves to aid in flotation and to keep the leaves near the water surface, ensuring ample light for photosynthesis.
  • Feature small roots since they can absorb nutrients directly from the surrounding water through their tissues.
  • Stomata are typically open continuously and are predominantly located on the upper epidermis of the leaf, facilitating efficient gas exchange with the atmosphere.

Xerophytes

Plants adapted to thrive in very arid environments possess specific features that enable them to survive with minimal water supply:

• Thick Waxy Cuticle: The plant's outer layer has a thick waxy cuticle that serves a dual purpose. Firstly, it acts as a barrier to prevent water loss through evaporation. Secondly, its shiny surface reflects heat, helping to reduce temperature.
• Sunken Stomata: Some plants have stomata (tiny pores for gas exchange) that are located in pits within the epidermis. This design traps moist air, increasing the diffusion pathway and decreasing the rate of evaporation.
• Leaf Structure: Certain plants have leaves that are rolled inward, with stomata positioned inside and covered by a layer of hairs. This configuration traps moist air, creating a barrier against air movement that would otherwise lead to excessive transpiration.
• Small Leaves: Many xerophytic plants feature small, needle-shaped leaves that minimize surface area, thereby reducing the area available for evaporation.
• Extensive Shallow Roots: These plants develop shallow but widespread root systems that facilitate rapid absorption of water when it becomes available, such as during rainfall.
• Thickened Leaves or Stems: Some species have leaves or stems with specialized cells that store water, providing a reservoir for times of drought.

Xerophytes are adapted to live in extremely dry conditions such as deserts