3,3 Plant adaptations to water availability

Question 1

what are the three types of plants?

Answer 1

hydrophytes
mesophytes
xerophytes

Question 2

what are hydrophytes?

Answer 2

water plants

Question 3

what are xerophytes?

Answer 3

plants living in dry conditions

Question 4

what are mesophytes?

Answer 4

plants living in normal conditions

Question 5

what is diffusion rate affected by?

Answer 5

surface area
difference in concentration
length of diffusion path

Question 6

plants have a waxy cuticle to prevent water loss, how does this help?

Answer 6

reduces transpiration from leaf surfaces

Question 7

how can stomata reduce water loss?

Answer 7

stomata on the underside of a leaf can be closed to prevent loss of water vapour

Question 8

give some examples of xerophytes:

Answer 8

conifers
marram grass
cacti

Question 9

how do hairs or spines reduce water loss?

Answer 9

increase layer of warm air around the leaf trapping water molecules

Question 10

xerophytes have a thick waxy cuticle what does this help do?

Answer 10

minimise water loss

Question 11

what do many xerophytes have relating to stomata?

Answer 11

sunken stomata in pits

Question 12

why do sunken stomata in pits help xerophytes conserve water?

Answer 12

minimise air movement
microclimate of humid air
reduces water potential gradient - reducing transpiration

Question 13

a lot of xerophytes have reduced numbers of stomata what does this do?

Answer 13

reduces transpiration

reduces gas exchange capabilities

Question 14

xerophytes also have reduced leaf area what does this do?

Answer 14

reduce water loss -small sa:v ratio

Question 15

some xerophytes have hairy leaves how does this reduce water loss?

Answer 15

microclimate of still air
reducing water vapour potential gradient
minimising water lost by transpiration

Question 16

how do xerophytes conserve water with curled leaves?

Answer 16

confines stomata in microclimate of still humid air reducing diffusion of water vapour from stomata

Question 17

some xerophytes are succulent plants, how do they conserve water?

Answer 17

store it in specialised parenchyma tissue in stems and roots to be used during times of drought

Question 18

how do some xerophytes prevent water loss by leaf loss?

Answer 18

they lose their leaves when water isn’t available

Question 19

what are some root adaptations of xerophytes to prevent water loss?

Answer 19

long roots can access water a long way below surface

widespread shallow roots absorb available water from rain showers before it evaporates

Question 20

how do some xerophytes avoid the problem of water loss?

Answer 20

losing leaves or become dormant
or die leaving seeds behind to germinate
other plants survive as bulbs e.g daffodils

Question 21

give examples of hydrophytes:

Answer 21

water lilies
water cress
duckweeds
yellow iris

Question 22

why is it important in surface water plants that their leaves float?

Answer 22

can get light needed for photosynthesis

Question 23

hydrophytes have a very thin or no waxy cuticle, why?

Answer 23

they don’t need to conserve water there is always an availability

Question 24

hydrophytes also have many open stomata on their upper surfaces, what does this do?

Answer 24

maximises gaseous exchange
always water available so turgor loss isn’t a problem
upper surfaces - in contact with air

Question 25

why do hydrophytes have reduced structure to the plant?

Answer 25

no need

water supports

Question 26

some hydrophytes have wide, flat leaves, why?

Answer 26

capture as much light as possible

Question 27

some hydrophytes have small roots, why?

Answer 27

so water can diffuse directly into stem and leaf tissue so less need for uptake by roots

Question 28

some hydrophytes have large surface area of stems and roots, why?

Answer 28

maximises area for photosynthesis and O2 to diffuse in

Question 29

some hydrophytes have air sacs why?

Answer 29

enable leaves and flowers to float

Question 30

some hydrophytes have arenchyma what is this?

Answer 30

specialised parenchyma tissue

Question 31

why do some hydrophytes have parenchyma?

Answer 31

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