The Adaptations of Plants to the Availability of Water

• Define Hydathode:

  A structure found at the tips of leaves which releases water droplets to evaporate from the leaf surface
• Define Succulent plant:

  A plant that stores water in their roots, stems, and leaves
• Describe the adaptations of succulent plants, such as cacti:

  • Roots are widespread on the surface of the ground = to get any rainfall
  • Green stems = for photosynthesis
  • Leaves are reduced to spines = reduces surface area, less water loss
  • Stems are ribbed or fluted = enables it to expand when water is available
• Define Hydrophyte:

  A plant adapted to living in water or on very wet ground
• Describe the adaptations of hydrophytes:

  • very thin or no waxy cuticle = no need to conserve water
  • open/ lots of stomata = found on the upper epidermis to maximise gas exchange
  • Wide and flat leaves = provides a large surface area for light absorption
  • Air sacs = enables leaves to stay afloat
  • large air spaces = increases buoyancy supported by surrounding water, allows oxygen to diffuse quickly to the roots
• Define Xerophyte:

  A plant adapted to living in dry conditions
• Describe the adaptations of xerophytes:

  • Less or smaller leaves = reduces the surface area for water loss
  • densely packed spongy mesophyll layer = reduces surface area
  • high salt concentration in leaves = reduces evaporation
  • thick waxy cuticles = hydration, prevent water loss via evaporation
  • Closed/ sunken stomata= prevents water loss
  • Long tap roots = to reach deep underground water
  • Stomata has hairs = traps moist air, reducing the water vapour potential
  • rolls their leaves = reduces the exposure of lower epidermis to the atmosphere, traps air, maintains moisture, becomes humid
• The adaptations for xerophytes serve to minimise water loss and the need for water uptake
• Outline what happens if a plant loses too much water?

  • lose turgidity
  • become plasmolysed
  • wilt
  • die
• Define Wilting in plants:

  The loss of rigidity of non-woody parts of plants due to lack of water
• How do deciduous trees reduce water loss?

  By shedding their leaves in the winter
• Define Halophyte:

  A plant adapted to living in salty conditions
• Define Mesophyte:

  A plant neither adapted to dry nor wet conditions
• Define Terrestrial plants:

  Plants that grow on, in, or from land
• What adaptation do the seeds of xerophytes have?

  They germinate only when it rains to give their new plants the best chance of survival
• Gas exchange happens through the stomata in plants
• What type of plants does this cell belong to?

  Hydrophytes

  
• What type of plants does this cell belong to?

  Mesophyte

  
• What type of plants does this cell belong to?

  xerophyte

  
• What type of plants does this cell belong to?

  Hydrophytes

  
• What are the walls of sieve tube elements made out of?

  Cellulose
• Plasmodesmata allows the cytoplasm to be shared between companion cells and sieve tube elements.
• Companion cells are connected to sieve tube elements via plasmodesmata