Xerophytes – adapted to arid conditions:

Question 1

Adaptations – reduce transpiration:

Answer 1

• Hairy leaves – traps water vapour/moisture by reducing air movement, reduces water vapour potential gradient.
• Less stomata – reduced diffusion of water vapour.
• Stomata in pits – pits trap water vapour (increased water vapour concentration).
• Stomata close during hot days/when water availability low.
• Stomata mostly on lower epidermis – cooler, less sun exposure, reduces diffusion/gas exchange.
• Rolled leaves – reduce exposed SA, trap water vapour.
• High solute/salt concentration in cells – reduces water potential in leaf cells, reducing evaporation of
  water (reduces water vapour gradient).
• Thick waxy cuticle – impermeable to water evaporation.
• Small leaves/needles (spines) – reduce SA, reduce evaporation & transpiration.
• Dense spongy mesophyll – few air spaces so less surface area for evaporation of water.
• Widespread roots – to take advantage of any rainfall.
• Long tap root – reach deep water underground.

Question 2

Marram Grass:

Answer 2

Marram Grass: Lives on sand dunes, little water (drains away quickly), sand may be salty & often very windy.

Question 3

Cacti:

Answer 3

Cacti: Succulents – store water in stems which become fleshy/swollen. The stem is often ribbed so it can expand when water is available. Stem can photosynthesise as leaves are reduced to spines.