transport in plants

Question 2

why do plants need a transport system

Answer 2

need to transport substances to other parts of the plant, get rid of waste products, high metabolic rate, multicellular, small SA;V ratio

Question 3

what does xylem tissue transport

Answer 3

water and mineral ions

Question 4

what does phloem tissue transport

Answer 4

sugars (sucrose)

Question 5

where are the xylem and phloem found in the root

Answer 5

at the centre, to provide support

Question 6

where are the xylem and phloem found in the stem

Answer 6

near outside to prevent stem bending

Question 7

where are xylem and phloem found in the leaf

Answer 7

make up a network of veins

Question 8

what are the adaptations of xylem vessels

Answer 8

no end walls between cells to allow water to pass through easily, cells are dead, cell walls thickened with lignin to add support, small pits in walls have no lignin which allows other cells to be supplied with water

Question 9

how do sieve tube elements act as an adaptation for phloem tissue

Answer 9

living cells, ‘sieve’ parts are end walls with lots of holes to allow solutes to pass through, no nucleus and are joined by cytoplasm of adjacent cell

Question 10

how do companion cells act as an adaptation for phloem tissue

Answer 10

one companion cell for every sieve tube element as they carry out living functions for both themselves and sieve elements, e.g provide energy for active transport of solutes

Question 11

how does water enter a plant

Answer 11

water enters root hair cell
passes through the root cortex, including the endodermis to reach the xylem, via osmosis

Question 12

describe how water moves through the symplast pathway

Answer 12

goes through the living parts of cells (the cytoplasm)
cytoplasm of neighbouring cells connect through plasmodesmata

Question 13

describe how water moves through the apoplast pathway

Answer 13

moves through dead parts of the cell (cell walls)
when water gets to the endodermis cells in the root, water os blocked by a waxy strip in the cells walls called the Casparian strip and water has to take the symplast pathway

Question 14

what is the movement of water from roots to leaves called

Answer 14

the transpiration stream

Question 15

how does cohesion and tension help water move up plants

Answer 15

water evaporates from leaves (transpiration)
this creates a tension which pulls more water into the leaf
cohesion allows more water molecules to be pulled into the leaf

Question 16

why does transpiration happen

Answer 16

result of gas exchange
plant opens its stomata to let in CO2 so that it can produce glucose
this also lets water out, as it travels down the water potential gradient

Question 17

what factors affect transpiration rate and how do they affect it

Answer 17

light intensity- more light= faster transpiration as stomata open when its light
temperature- higher temp= faster rate as molecules have more kinetic energy and increases w.p gradient
humidity-lower humidity= faster rate as water po. gradient is increased
wind- higher wind= faster rate as water molecules are moved so w.p gradient increases

Question 18

what are xerophytes

Answer 18

plants adapted to live in dry climates

Question 19

how are cacti adapted

Answer 19

have a thick waxy layer to reduce water loss by transpiration
have spines instead of leaves to reduce surface area for water loss
close their stomata at hot times of th day when transpiration rates are at their highest

Question 20

how is marram grass adapted

Answer 20

sunken pits so sheltered from the wind which traps moist air so lowers w.p gradient
layer of hairs to trap moist air around stomata
roll leaves to protect from wind and trap moist air
thick waxy layer

Question 21

what are hydrophytes

Answer 21

plants that live in aquatic habitats

Question 22

what are some adaptations sof hydrophytes

Answer 22

air spaces to help plants float and act as oxygen storage for respiration
stomata present on upper surface to maximise as exchange
have flexible leaves and stems to prevent damage from water currents

Question 23

what is translocation

Answer 23

the movement of dissolved substances to where they’re needed in a plant

Question 24

dissolved substances are often known as what

Answer 24

assimilates

Question 25

what is a ‘source’

Answer 25

where a substance is made

Question 26

what is a ‘sink’

Answer 26

where the substance is used up

Question 27

explain the mass flow hypothesis

Answer 27

active transport is used to load the solutes into the sieve tubes of the phloem at the source
this lowers the water potential inside sieve tubes so water enters tubes via osmosis from the xylem and companion cells
this creates high pressure inside sieve tubes at source end
at sink end solutes move in via diffusion as they are usually at higher conc. in phloem than surrounding tissue at sink
remove of solutes increases water potential inside sieve tubes so water leaves via osmosis
this lowers pressure in sieve cells
the result is a pressure gradient from source end to sink
this gradient pushes solutes along sieve tubes towards the sink where they are used
the higher the conc. of sucrose at the source the higher the rate of translocation

Question 28

where is active loading used

Answer 28

at the source to move substances into the sieve cell from surrounding tissue and from companion cells into the sieve tubes against the conc. gradient

Question 29

how is sucrose moved

Answer 29

active transport and co transport proteins

Question 30

how is sucrose moved through active loading

Answer 30

H+ ions are used to move sucrose against the conc. gradient
in the companion cell active transport is used to actively transport hydrogen ions out of the cell and into surrounding tissue cells, which creates a conc. gradient
an H+ ion binds to a co-transport protein in the companion cell membrane and re enters the cell and at the same time a sucrose molecule bind to the H+ ion (against conc. gradient)
sucrose molecules are then transported out of the companion cells and into the sieve tube elements in the same process