3,3 Plant adaptations to water availability Flashcards
what are the three types of plants?
hydrophytes
mesophytes
xerophytes
what are hydrophytes?
water plants
what are xerophytes?
plants living in dry conditions
what are mesophytes?
plants living in normal conditions
what is diffusion rate affected by?
surface area
difference in concentration
length of diffusion path
plants have a waxy cuticle to prevent water loss, how does this help?
reduces transpiration from leaf surfaces
how can stomata reduce water loss?
stomata on the underside of a leaf can be closed to prevent loss of water vapour
give some examples of xerophytes:
conifers
marram grass
cacti
how do hairs or spines reduce water loss?
increase layer of warm air around the leaf trapping water molecules
xerophytes have a thick waxy cuticle what does this help do?
minimise water loss
what do many xerophytes have relating to stomata?
sunken stomata in pits
why do sunken stomata in pits help xerophytes conserve water?
minimise air movement
microclimate of humid air
reduces water potential gradient - reducing transpiration
a lot of xerophytes have reduced numbers of stomata what does this do?
reduces transpiration
reduces gas exchange capabilities
xerophytes also have reduced leaf area what does this do?
reduce water loss -small sa:v ratio
some xerophytes have hairy leaves how does this reduce water loss?
microclimate of still air
reducing water vapour potential gradient
minimising water lost by transpiration
how do xerophytes conserve water with curled leaves?
confines stomata in microclimate of still humid air reducing diffusion of water vapour from stomata
some xerophytes are succulent plants, how do they conserve water?
store it in specialised parenchyma tissue in stems and roots to be used during times of drought
how do some xerophytes prevent water loss by leaf loss?
they lose their leaves when water isn’t available
what are some root adaptations of xerophytes to prevent water loss?
long roots can access water a long way below surface
widespread shallow roots absorb available water from rain showers before it evaporates
how do some xerophytes avoid the problem of water loss?
losing leaves or become dormant
or die leaving seeds behind to germinate
other plants survive as bulbs e.g daffodils
give examples of hydrophytes:
water lilies
water cress
duckweeds
yellow iris
why is it important in surface water plants that their leaves float?
can get light needed for photosynthesis
hydrophytes have a very thin or no waxy cuticle, why?
they don’t need to conserve water there is always an availability
hydrophytes also have many open stomata on their upper surfaces, what does this do?
maximises gaseous exchange
always water available so turgor loss isn’t a problem
upper surfaces - in contact with air
why do hydrophytes have reduced structure to the plant?
no need
water supports
some hydrophytes have wide, flat leaves, why?
capture as much light as possible
some hydrophytes have small roots, why?
so water can diffuse directly into stem and leaf tissue so less need for uptake by roots
some hydrophytes have large surface area of stems and roots, why?
maximises area for photosynthesis and O2 to diffuse in
some hydrophytes have air sacs why?
enable leaves and flowers to float
some hydrophytes have arenchyma what is this?
specialised parenchyma tissue
why do some hydrophytes have parenchyma?
has large air spaces
making leaves and stems more buoyant
form low resistance pathway for movement of O2 to tissues below water helping plants cope with anoxic (low O2) conditions
