AQA AS Biology Xerophytes Revision.

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  • Created by: Chloe
  • Created on: 30-05-13 17:14



  • Conserve water while maximising gas exchange efficiency.
  • Deep or wide spread roots suffice for many but plants without plentiful water supply develop adaptions to limit water loss.Adaptions help; water uptake, store water, reduce transpiration.
  • STOMATA IN PITS: Trap moist air next to leaf, reduce water potential gradient. Reduce water lost via transpiration.
  • REDUCED SA:V RATIO OF LEAVES: Having small and cylindrical leaves as opposed to flat and broad, rate of water loss can be reduced. As smaller SA:V the slower the rate of diffusion, water moves out of plant slower.


Other information              

  • A THICK CUTICLE: thicker waxy cuticles reduce water lost across waxy cuticle.
  • ROLLING LEAVES: rolled leaves create still water saturated air around the stomata reducing water potential gradient and reducing transpiration.
  • HAIRY LEAVES: thick layers of hair trap moist air next to leaf, reducing water potential gradient between inside + outside of leaf, so less water lost via Transp.
  • Transpiration occurs through stomata and can be increased/decreased by environmental factors eg heat, wind, sun etc. humidity and water potential gradients can help reduce rate of transpiration and therefore water loss.


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