Plant organisation 2.0

Question 1

what do phloem cells consist of?

Answer 1

living cells

Question 2

how are the sieve tubes specialised for transport?

Answer 2

they have no nuclei

Question 3

describe the structure of a sieve tube

Answer 3

-each sieve tube has a perforated end so its cytoplasm connects one cell to the next.

Question 4

how are sucrose and amino acids translocated within the sieve tubes?

Answer 4

through their cytoplasm

Question 5

what does transport of substances in the phloem require?

Answer 5

energy

Question 6

what do the companion cells do to provide the energy needed to transport substances?

Answer 6

attach to each sieve tube to provide this energy

Question 7

what type of transport process happens within the xylem and phloem?

Answer 7

xylem = physical/ passive process
phloem = active process

Question 8

what happens to water when plants open their stomata to let CO2 in? (2)
what is this process called?

Answer 8

-water on the surface of spongy and palisade mesophyll cells evaporates
-and diffuses out of the leaf.
-transpiration

Question 9

where is water drawn from to replace the water lost from the leaves?

Answer 9

the xylem

Question 10

what is between the water molecules which makes them strongly attracted to one another?
because of what?

Answer 10

strong cohesion between the molecules
-because of hydrogen bonding

Question 11

describe the growth of root hair cells

Answer 11

they grow between soil particles and absorb water and minerals from the soil.

Question 12

which 4 factors affect transpiration?

Answer 12

temperature
humidity
air movement
light intensity

Question 13

what would need to happen to the temperature in order to increase transpiration rate?

Answer 13

increase it

Question 14

why would an increase in temperature increase transpiration rate? (3)

Answer 14

Increases molecular movement so that:
-more water molecules evaporate from cell surfaces
-the rate of diffusion of water molecules from the leaf is increased

Question 15

what would need to happen to the humidity in order to increase transpiration rate?

Answer 15

decrease it

Question 16

why does a decrease in humidity increase transpiration rate? (2)

Answer 16

-reduces the concentration of water molecules outside the leaf
-diffusion of water from the leaf increases

Question 17

what would need to happen to the air movement in order to increase transpiration rate?

Answer 17

increase it

Question 18

why does an increase in air movement increase transpiration rate?

Answer 18

-removes water vapour from leaf surfaces
-more water diffuses from the leaf because a high concentration gradient is maintained

Question 19

what would need to happen to the light intensity in order to increase transpiration rate?

Answer 19

increase it

Question 20

why does an increase in light intensity increase transpiration rate?

Answer 20

-Increases the rate of photosynthesis
-stomata open so that water diffuses out of the leaf

Question 21

what can the stems of cacti store which makes them well adapted to their environment?

Answer 21

they can store water

Question 22

why are the root systems of cacti beneficial? (2)

Answer 22

Widespread or very deep root systems
-that can collect water from a large area or from very deep underground.

Question 23

why are the spines of cacti beneficial?

Answer 23

they are modified leaves

Question 24

what are the features of modified leaves & how are they useful? (2)

Answer 24

-minimise the surface area and so reduce water loss.
-protect the cacti from animals that might eat them.

Question 25

what are the leaves (spines) of cacti adapted to have?
-why?

Answer 25

Very thick, waxy cuticle
-to reduce water loss by evaporation.

Question 26

what do cacti have a reduced number of across their spines?
-why?

Answer 26

Reduced number of stomata
-to reduce water loss by transpiration.

Question 27

describe the movement of sucrose from where it is made to sinks: (6)

Answer 27

-sucrose moves from source into sieve tubes via active transport
-energy is provided by the companion cells (attached to sieve)
-water moves into the top of phloem from nearby xylem by osmosis
-water moves from high conc in xylem to low conc in phloem
-pushes sucrose towards sinks (up or down)
-sucrose enters sink cells by diffusion or active transport (depending on concentration levels)