Brent Cornell

    
Desert plants (xerophytes) and plants that grow in high salinity (halophytes) possess various adaptations for water conservation

• 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

Xerophytes

Xerophytes are plants that can tolerate dry conditions (such as deserts) due to the presence of a number of adaptations:

• Reduced leaves – reducing the total number and size of leaves will reduce the surface area available for water loss
• Rolled leaves – rolling up leaves reduces the exposure of stomata to the air and hence reduces evaporative water loss
• Thick, waxy cuticle – having leaves covered by a thickened cuticle prevents water loss from the leaf surface 
• Stomata in pits – having stomata in pits, surrounded by hairs, traps water vapour and hence reduces transpiration
• Low growth – low growing plants are less exposed to wind and more likely to be shaded, reducing water loss
• CAM physiology – plants with CAM physiology open their stomata at night, reducing water loss via evaporation

Halophytes

Halophytes are plants that can tolerate salty conditions (such as marshlands) due to the presence of a number of adaptations:

• Cellular sequestration – halophytes can sequester toxic ions and salts within the cell wall or vacuoles
• Tissue partitioning – plants may concentrate salts in particular leaves, which then drop off (abscission)
• Root level exclusion – plant roots may be structured to exclude ~95% of the salt in soil solutions
• Salt excretion – certain parts of the plant (e.g. stem) may contain salt glands which actively eliminate salt
• Altered flowering schedule – halophytes may flower at specific times (e.g. rainy seasons) to minimise salt exposure 

Overview of Water Conservation Adaptations