module 3 - 9.5 potometers & specialist plants

Question 1

what are the variables influencing plant growth?

Answer 1

• light intensity
• temperature
• humidity (relative)
• air movement/ wind speed

Question 2

why is the plant stem cut at an angle?

Answer 2

to increase surface area

Question 3

how does equilibration occur?

Answer 3

when we let water evaporate off leaves

Question 4

why is the measurement of the bubble every minute, only an estimation?

Answer 4

because photosynthesis is also happening

Question 5

what does a potometer measure?

Answer 5

(rate of) transpiration

Question 6

what is the ruler used for?

Answer 6

to measure distance travelled by bubble in tube

Question 7

what is a xerophyte?

Answer 7

plants in dry habitats that have adaptations to allow them to live and reproduce when water availability is very low

Question 8

what are some ways that xerophytes conserve water?

Answer 8

• thick waxy cuticle
• sunken stomata
• reduced number of stomata
• reduced leaves
• hairy leaves
• curled leaves
• succulents
• leaf loss

Question 9

how does a thick waxy cuticle help xerophytes to conserve water?

Answer 9

minimises water loss through leaves

Question 10

how does sunken stomata help xerophytes to conserve water?

Answer 10

• reduces air movement, providing microclimate of still, humid air
• reduces water potential gradient (so reduces transpiration)

Question 11

how does a reduced number of stomata help xerophytes to conserve water?

Answer 11

• reduces water loss by transpiration
• reduces gas exchange capabilities

Question 12

how does reduced leaves help xerophytes to conserve water?

Answer 12

• reduces SA:V ratio
• minimises water loss by transpiration

Question 13

how do hairy leaves help xerophytes to conserve water?

Answer 13

• creates microclimate of still, humid air to reduce water vapour potential gradient
• minimises water loss by transpiration

Question 14

how do curled leaves help xerophytes to conserve water?

Answer 14

restricts all stomata (within microclimate) to reduce diffusion of water vapour

Question 15

how do succulents help xerophytes to conserve water?

Answer 15

succulent plants store water in specialised parenchyma tissue in their stems and roots

Question 16

how does leaf loss help xerophytes to conserve water?

Answer 16

prevents water loss through leaves

Question 17

what are 3 examples of xerophytes?

Answer 17

• conifers
• cacti
• plants in very cold and icy conditions

Question 18

what are the root adaptations to help xerophytes to conserve water?

Answer 18

• 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

Question 19

what are hydrophytes?

Answer 19

plants living in water (submerged, on surface, or on edge of bodies of water)

Question 20

why must surface water plants have leaves that float?

Answer 20

to get light needed for photosynthesis

Question 21

why is water logging a problem?

Answer 21

air spaces of plants need to be filled with air not water

Question 22

what are the adaptations of hydrophytes?

Answer 22

• very thin/ no waxy cuticle
• always-open stomata on upper surface
• reduced structure
• wide, flat leaves
• small roots
• large SA
• air sacs

Question 23

why is a thin/ no waxy cuticle an adaptation to help hydrophytes?

Answer 23

don’t need to conserve water, water loss by transpiration isn’t a problem

Question 24

why is always-open stomata on upper surface an adaptation to help hydrophytes?

Answer 24

maximising number of stomata maximises gaseous exchange

Question 25

why is a reduced structure an adaptation to help hydrophytes?

Answer 25

water supports leaves and plants, no need for strong supporting structures

Question 26

why are wide, flat leaves an adaptation to help hydrophytes?

Answer 26

large SA to capture more sunlight

Question 27

why is small roots an adaptation to help hydrophytes?

Answer 27

shorter diffusion distance, water diffuses directly into stem and leaf tissue (no uptake by roots)

Question 28

why is a large SA an adaptation to help hydrophytes?

Answer 28

maximises area for photosynthesis and for oxygen to diffuse into submerged plants

Question 29

why are air sacs an adaptation to help hydrophytes?

Answer 29

• 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