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plant adaptations to water availability (xerophytes (reduced leaves…
plant adaptations to water availability
xerophytes
plants in habitats where water is not freely available e.g. dry, cold, icy
e.g. cacti, marram grass
hairy leaves
create a microclimate of still, humid air
reduce water potential gradient and therefore reduced transpiration
e.g marram grass
reduced leaves
reducing leaf area reduces water loss
reduced SA:V ratio
e.g. conifers
curled leaves
confines all stomata to a microenvironment of still, humid air
reduce diffusion of water vapour from stomata
e.g. marram grass
reduced numbers of stomata
reduce water loss by transpiration but also reduce gas exchange abilities
succulents
store water in specialised parenchyma tissue in stems and roots
water is stored when in plentiful supply - used in times of drought
e.g. desert cacti, aloes
sunken stomata
stomata located in pits
reduce air movement
produces microclimate of still, humid air
reduces water vapour potential gradient
reduces transpiration
e.g. marram grass, cacti
leaf loss
lose leaves when water is not available
e.g. desert trees
thick waxy cuticle
up to 10% of water loss by transpiration is through the cuticle
e.g. evergreen plants
help to survive hot dry summers and cold winters
avoiding the problem
lose leaves and become dormant
die completely - leave seeds to germinate and grow when rain falls
survive as storage organs
e.g. potatoes, onions
root adaptations
long roots - access water a long way below the surface
widespread, shallow roots - absorb available water before rain shower evaporates
e.g. cacti
hydrophytes
plants that live in water
e.g. water lilies, water cress
reduced structure to the plant
water support leaves and flowers so no need for strong supporting structures
many always open stomata on upper surfaces
maximises gas exchange
no risk of loss of turgor - always abundance of water available
guard cells inactive
e.g. water lilies - stomata on upper surface so in contact with air
wide, flat leaves
capture as much light as possible
very thin or no waxy cuticle
water loss through transpiration is not an issue
small roots
water can diffuse directly into stem and leaves - less need for uptake by roots
large surface area of stems and roots under water
maximises area for photosynthesis and for oxygen to diffuse into submerged plants
air sacs
enable leaves and flowers to float on surface of water
aerenchyma
specialised parenchyma tissue forms in leaves, stems and roots
many large air spaces
formed by apoptosis (cell death) in normal parenchyma
functions
make leaves and stems more buoyant
form low resistance internal pathway for movement of substances e.g. oxygen to tissues below water
helps plant cope with anoxic (low oxygen) conditions in mud
e.g. rice