3.1.3 transport in plants

Question 1

list the features of a dicotyledonous root

Answer 1

epidermis
cortex
root hair with meristem and root cap
endodermis
casparian strip
pericycle
xylem and phloem

Question 2

list the features of a dicotyledonous stem

Answer 2

epidermis
cortex
xylem - vascular bundle
cambium
pith

Question 3

list the features of a dicotyledonous leaf

Answer 3

waxy cuticle
upper epidermis
palisade cell layer
spongy layer
vascular bundle
lower epidermis
guard cells + stomata

Question 4

what is transpiration

Answer 4

loss of water vapour from stems and leaves due to evaporation

Question 5

what factors affect transpiration rate

Answer 5

light intensity
relative humidity
temperature
movement of air

Question 6

how do we measure transpiration rate

Answer 6

potometer - movement of air bubble along cylinder due to water evaporation
rate = volume/time

Question 7

how do you measure the volume of a cylinder

Answer 7

πr² x length

Question 8

what is a mass potometer

Answer 8

plastic wrap around bottom to prevent evaporation from soil and place pot on balance
mass decreases over time due to transpiration

Question 9

explain the process of transpiration

Answer 9

water evaporates from leaf cells, decreasing water potential
water moves from xylem into leaf cells via osmosis
as water moves into leaf cells it pulls water molecules in xylem behind it upwards due to cohesive forces
water moves into root hair cell by osmosis to replace water that’s moved up the xylem
as water moves through plant it helps transport minerals dissolved in it towards leaves

Question 10

how do mineral ions enter a plant

Answer 10

by active transport into the root hair cells which causes cell to have a lower water potential than soil

Question 11

how does water move into a root hair cell

Answer 11

by osmosis because it goes from a high water potential in soil to low water potential in root hair cell (down water potential gradient)

Question 12

what does symplastic mean

Answer 12

water moves through cytoplasm by osmosis down the water potential gradient from root hair cell to xylem

Question 13

what does apoplastic mean

Answer 13

water moves through cell walls due to cohesive forces like capillary action
stops at endodermis as casparian strips act as a barrier

Question 14

what is translocation

Answer 14

movement of sucrose from cells where sugars are made (source) to cells that need them (sink)

Question 15

what is the mass flow hypothesis

Answer 15

photosynthesis produces glucose (makes sucrose when added to fructose)
sucrose dissolves to phloem via symplast pathway and companion cells
sucrose levels increase so water potential decreases
water moves by osmosis from xylem
increases water levels which increases hydrostatic pressure so there’s a pressure gradient between source and sink
sucrose moves down gradient and diffuses into sink so water potential of phloem increases and water leaves phloem by osmosis

Question 16

what is active loading for

Answer 16

sucrose transported by the apoplastic pathway

Question 17

describe the process of active loading

Answer 17

active transport of H+ out of cytoplasm
high H+ concentration out of cell#
H+ diffuses down concentration gradient - sucrose is cotransported
sucrose in cytoplasm

Question 18

what are xerophytes

Answer 18

plants that have evolved to live in condition where water is very scarce

Question 19

what are the adaptations of cacti

Answer 19

leaves replaced with spikes
photosynthesis occurs in stem
stomata in stem surface sunk into pits - only open t night
spines to trap moist air
thick waxy cuticle
long shallow roots or deep roots for storage

Question 20

what are the adaptions of marram grass

Answer 20

leaves roll into tube with stomata inside traps moist air
thick waxy cuticle
long roots deep to find water or shallow to retain water in sand