B8 - transport in plants (transpiration & translocation)

Question 1

function of xylem

Answer 1

carry water & mineral salts from the roots to the leaves

Question 2

function of phloem

Answer 2

carry sucrose & amino acids from the sources to the sinks
source: eg. leaves
sinks: eg. roots, flowers, fruit

Question 3

5 things about xylem vessels

Answer 3

-transports water & dissolved minerals
-transported from root to leaves
-dead = no cytoplasm, nucleus, cell membrane
-lignin - strengthens cellulose cell walls - adds support
-no end cell walls = hollow tube

Question 4

5 things about phloem sieve tube

Answer 4

-transports sucrose & amino acids
-transported from source to sink
-has a companion cell
-sieve plates have holes
-sieve tubes are living;; thin strands of cytoplasm, no nucleus & some organelles

Question 5

locations of xylem vessel in:
root
stem
leaf

Answer 5

root - X shape
stem - inner
leaf - top

Question 6

locations of phloem vessel in:
root
stem
leaf

Answer 6

root - outer of X
stem - outer
leaf - bottom

Question 7

function of root hair cell

Answer 7

-minerals enter by active transport
-water enters by osmosis

Question 8

adaptation of root hair cell

Answer 8

-larger surface area = faster absorption
-lots of mitochondria = more respiration = more E for active transport

Question 9

pathway for water into the plant

Answer 9

-water enters root hair cell by osmosis
-root hair cell is hypertonic to surrounding soil water = low wp
-water moves through root cortex by osmosis
-water enters xylem vessel & rises by transpiration pull
-water moves in spongy mesophyll by osmosis
-water evaporates into spaces above stomata
-water leaves from stomata by diffusion

Question 10

define transpiration

Answer 10

-loss of water vapor from plant leaves by evaporation of water at the surface of the mesophyll cells followed by diffusion of the water vapor through the stomata
-unidirectional

Question 11

does water loss = transpiration?

Answer 11

-no, some water could be used for photosynthesis
but we assume for most part

Question 12

explain the mechanism of water movement up the stem of a plant

Answer 12

-evaporation from leaves
-water molecules held tgt by cohesion
-pulls water molecules up the xylem

Question 13

process of transpiration

Answer 13

-water vapor diffuses out of the stomata after it evaporated in the spongey mesophyll
-this causes a transpiration pull om the water molecules because they are held together by cohesion
-water enter the plant down a concentration gradient through osmosis in the root hair cell

Question 14

factors of transpiration

Answer 14

-temperature
-humidity
-wind speed
-light intensity

Question 15

how does temperature affect transpiration

Answer 15

-more transpiration
-more thermal E for evaporation, more kinetic E for diffusion
-only up till optimum temp

Question 16

how does humidity affect transpiration

Answer 16

-less transpiration
-higher wp outside stomata, less steep concentration gradient, less diffusion
eg. monsoon

Question 17

how does wind speed affect transpiration

Answer 17

-more transpiration
-pocket of humid air (water vapor) is blown away, more steep concentration gradient, more diffusion

Question 18

how does light intensity affect transpiration

Answer 18

-increase transpiration
-darkness will cause stomata to close

Question 19

how to change the factors of transpiration

Answer 19

temp - thermostatically controlled water bath/ distance from a heater
humidity - plastic bag over the plant’s leaf
wind speed - use a fan with varying speed
light intensity - use a lamp

Question 20

cause of wilting

Answer 20

loss of water exceeds intake

Question 21

wilting events

Answer 21

-plant loses water, mainly by transpiration
-vacuole shrinks
-cell becomes flaccid (low water pressure)
-plant is no longer supported; wilts

Question 22

define translocation

Answer 22

-movement of sucrose & amino acids in phloem from sources to sinks
-bidirectional

Question 23

define sink & eg

Answer 23

-part of plant the uses/ stores sucrose/ amino acids
eg. fruit, flower, nector

Question 24

define source & eg

Answer 24

-part of plant the releases sucrose/ amino acids
eg. leaf, seed

Question 25

note: before the experiment, let the plant adjust to the change for 10min

Question 26

note: oil prevent water loss by evaporation

Question 27

features of a bubble potometer

Answer 27

-bung
-reservoir of water
-tap
-air bubble
-capillary tube

Question 28

units to measure rate of transpiration

Answer 28

mm/ min

Question 29

independent, dependent & control variables for wind speed effect on transpiration

Answer 29

independent: fan speed (0, 1, 2, 3)
dependent: distance the bubbles travels in 10 min
control: temp (thermostatically controlled water bath), humidity, light intensity, plant species, same no. of leaves (use same plant), distance btw fan & plant

Question 30

method for wind speed effect on transpiration

Answer 30

-set up the apparatus the diagram shows
-weight the whole apparatus at the start
-for each fan speed, leave it 10 min with 5 mins before the timer for equilibration
-weigh the apparatus again
-calculate the mass difference
-repeat for each fan speed 3 times & find the mean mass diff

Question 31

conclusion for wind speed effect on transpiration

Answer 31

-more fan speed, more water loss; faster evaporation & steeper concentration gradient

Question 32

3 ways to improve wind speed effect on transpiration experiment

Answer 32

-use a bubble potometer
-more repeats
-more fan speed