CIE IGCSE Biology: 复习笔记：18.1.3 Adaptive Features: Extended

Hydrophytes

• Plants adapted to live in extremely wet conditions
• Common adaptations include:
  • Large air spaces in their leaves to keep them close to the surface of the water where there is more light for photosynthesis
  • Small roots as they can also extract nutrients from the surrounding water through their tissues
  • Stomata usually open all the time and mainly found on the upper epidermis of the leaf where they can exchange gases much more easily with the air

   

Hydrophytes are adapted to live in wet conditions such as ponds

Xerophytes

• Plant adapted to live in extremely dry conditions
• Common adaptations include:
  • Thick waxy cuticle - the cuticle cuts down water loss in two ways: it acts as a barrier to evaporation and also the shiny surface reflects heat and so lowers temperature
  • Sunken stomata: stomata may be sunk in pits in the epidermis; moist air trapped here lengthens the diffusion pathway and reduces evaporation rate
  • Leaf rolled with stomata inside and an inner surface covered in hairs - traps moist air and prevents air movement across stomata which reduces transpiration
  • Small leaves: many xerophytic plants have small, needle-shaped leaves which reduce the surface area and therefore the evaporating surface
  • Extensive shallow roots allowing for the quick absorption of large quantities of water when it rains
  • Thickened leaves or stems which contain cells that store water

   

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

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