Water Conservation

• Desert plants and plants that grow in high salinity possess various adaptations for water conservation
• What are desert plants also known as?


  xerophytes
• What are plants that grow in high salinity also known as?


  halophytes
• Xerophytes will have high rates of transpiration due to the high temperatures and low humidity of desert environments
• Halophytes will lose water as the high intake of salt from the surrounding soils will draw water from plant tissue via osmosis
• Adaptations of xerophytes include: reduced leaves; rolled leaves; thick, waxy cuticle; stomata in pits; low growth; CAM physiology
• Reduced leaves help xerophytes tolerate dry conditions by: 


  reducing the total number and size of leaves, reducing the surface area available for water loss
• Rolled leaves help xerophytes tolerate dry conditions by: 


  reducing the exposure of stomata to the air, reducing evaporative water loss
• Thick, waxy cuticle help xerophytes tolerate dry conditions by:


  preventing water loss from the leaf surface 
• Having stomata in pits surrounded by hairs helps xerophytes tolerate dry conditions by:


  trapping water vapour, hence reducing transpiration
• Low growth helps xerophytes tolerate dry conditions by: 


  limiting exposure to wind and increasing likelihood of shade, reducing water loss
• CAM physiology helps xerophytes tolerate dry conditions by:


  allowing them to reduce water loss via evaporation by only opening stomata at night
• Halophytes are plants that can tolerate salty conditions (such as marshlands) due to the presence of a number of adaptations
• Cellular sequestration helps halophytes tolerate salty conditions by: 


  sequestering toxic ions and salts within the cell wall or vacuoles
• Tissue partitioning helps halophytes tolerate salty conditions by:

  concentrating salts in particular leaves, which then drop off in a process called abscission
• Root level exclusion helps halophytes tolerate salty conditions by: 


  structuring the plant's roots to exclude ~95% of the salt in soil solutions
• Salt excretion helps halophytes tolerate salty conditions by: 


  allowing the plant to actively eliminate salt through salt glands
• Altered flowering schedule helps halophytes tolerate salty conditions by:


  allowing plants to minimize salt exposure by only flowering at certain times when salt levels are low