Plant adaptation to water availability

Xerophytes

  • adapted to dry conditions

  • Thick waxy cuticle

    • minimise water loss

  • sunken stomata

    • reduces air movement/increases humidity

  • fewer stomata

    • decrease rate of transpiration

  • fewer leaves

    • decreases rate of transpiration

  • hairy leaves

    • increase local humidity - decreases transpiration

  • curled leaves

    • stomata inside the curled area traps moist air

  • succulents

    • water stored in specialised parenchyma in stems and roots

  • leaf loss

    • some plants drop their leaves when water not available and photosynthesise using trunk and branches

  • root adaptations

    • long roots to reach deep water

    • lots of wide shallow roots to absorb water before it evaporates from the surface

  • dormancy/death

    • some die back and wait until water available or produce seeds to replace themselves or as storage organs eg. bulbs

  • examples include cacti and marram grass

  • xerophytes

Hydrophytes

  • adapted to wet conditions/growing in water

  • very thin/no waxy cuticle

    • water loss not an issue

  • stomata on surface of leaf

    • maximises gaseous exchange into the air

  • stomata always open

    • maximises gaseous exchange

  • reduced structure

    • support provided by water

  • wide flat leaves

    • catch light for photosynthesis

  • small roots

    • water can diffuse straight into leaves and stems from the water

  • large surface area of roots and stems under water

    • increases area for diffusion and photosynthesis

  • air sacs

    • enables leaves and flowers to float to the surface

  • aerenchyma

    • air spaces in parenchyma creates buoyancy and allows for low resistance to the movement of substances eg oxygen to tissues

  • some plants eg mangroves have aerial roots as normal roots can become waterlogged

  • examples include water lily

  • hydrophytes