Adaptive Features Continued (Cambridge International IGCSE Biology)

Hydrophytes & xerophytes: Extended

Spec point — 18.1.3 · nan

Extended Tier Only

• Hydrophytes are plants adapted to live in extremely wet conditions
• Common adaptations include:

* Hydrophytes are adapted to live in wet conditions such as ponds*

• large air spaces in their leaves for flotation, to keep the leaves 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

• Xerophytes are plants 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 the temperature
  • sunken stomata - stomata may be sunk in pits in the epidermis; moist air trapped here lengthens the diffusion pathway and reduces the 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 allow for the quick absorption of large quantities of water when it rains or deep roots to reach deep water tables
  • thickened leaves or stems which contain cells that store water

An example of a xerophyte adapted to live in extremely dry conditions such as deserts.