module 3 - 9.5 potometers & specialist plants Flashcards
what are the variables influencing plant growth?
- light intensity
- temperature
- humidity (relative)
- air movement/ wind speed
why is the plant stem cut at an angle?
to increase surface area
how does equilibration occur?
when we let water evaporate off leaves
why is the measurement of the bubble every minute, only an estimation?
because photosynthesis is also happening
what does a potometer measure?
(rate of) transpiration
what is the ruler used for?
to measure distance travelled by bubble in tube
what is a xerophyte?
plants in dry habitats that have adaptations to allow them to live and reproduce when water availability is very low
what are some ways that xerophytes conserve water?
- thick waxy cuticle
- sunken stomata
- reduced number of stomata
- reduced leaves
- hairy leaves
- curled leaves
- succulents
- leaf loss
how does a thick waxy cuticle help xerophytes to conserve water?
minimises water loss through leaves
how does sunken stomata help xerophytes to conserve water?
- reduces air movement, providing microclimate of still, humid air
- reduces water potential gradient (so reduces transpiration)
how does a reduced number of stomata help xerophytes to conserve water?
- reduces water loss by transpiration
- reduces gas exchange capabilities
how does reduced leaves help xerophytes to conserve water?
- reduces SA:V ratio
- minimises water loss by transpiration
how do hairy leaves help xerophytes to conserve water?
- creates microclimate of still, humid air to reduce water vapour potential gradient
- minimises water loss by transpiration
how do curled leaves help xerophytes to conserve water?
restricts all stomata (within microclimate) to reduce diffusion of water vapour
how do succulents help xerophytes to conserve water?
succulent plants store water in specialised parenchyma tissue in their stems and roots
how does leaf loss help xerophytes to conserve water?
prevents water loss through leaves
what are 3 examples of xerophytes?
- conifers
- cacti
- plants in very cold and icy conditions
what are the root adaptations to help xerophytes to conserve water?
- long tap roots growing deep into the ground to access water far below surface
- mass of widespread, shallow roots with large SA to absorb any water before rain evaporates
what are hydrophytes?
plants living in water (submerged, on surface, or on edge of bodies of water)
why must surface water plants have leaves that float?
to get light needed for photosynthesis
why is water logging a problem?
air spaces of plants need to be filled with air not water
what are the adaptations of hydrophytes?
- very thin/ no waxy cuticle
- always-open stomata on upper surface
- reduced structure
- wide, flat leaves
- small roots
- large SA
- air sacs
why is a thin/ no waxy cuticle an adaptation to help hydrophytes?
don’t need to conserve water, water loss by transpiration isn’t a problem
why is always-open stomata on upper surface an adaptation to help hydrophytes?
maximising number of stomata maximises gaseous exchange
why is a reduced structure an adaptation to help hydrophytes?
water supports leaves and plants, no need for strong supporting structures
why are wide, flat leaves an adaptation to help hydrophytes?
large SA to capture more sunlight
why is small roots an adaptation to help hydrophytes?
shorter diffusion distance, water diffuses directly into stem and leaf tissue (no uptake by roots)
why is a large SA an adaptation to help hydrophytes?
maximises area for photosynthesis and for oxygen to diffuse into submerged plants
why are air sacs an adaptation to help hydrophytes?
- enables leaves to float on surface
- aerenchyma packing tissue forms in leaves, stems and roots
- makes leaves and stems more buoyant
- forms low-resistance internal pathway for movement of substances
