Transport in plants

Question 1

What is the cuticle

Answer 1

A waterproofing layer of cutin

Question 2

What is the epidermis

Answer 2

A single layer of cells, transparent to sunlight
secretes cutin

Question 3

What is the parenchyma

Answer 3

Unspecialised cells
Make up the pith and cortex

Question 4

What is the function of the xylem

Answer 4

To transport water and minerals up the plant

Question 5

What is the structure of the xylem

Answer 5

Made of elongated lignified dead cells
Undergoes spiral lignification
Inside is Hydrophillic

Question 6

What is the purpose of spiral lignification within xylem vessels

Answer 6

Lignification -waterproofing, prevents collapse, provides adhesion
Spiral - allows xylem to stretch as plant grows, allows branch/stem to bend

Question 7

What are the two types of phloem cells

Answer 7

Companion cells
Sieve tube elements

Question 8

What are the features of the sieve tube elements in the phloem

Answer 8

little cytoplasm
no nucleus
have mitochondria + RER
have pores
have sieve plates

Question 9

Features of the companion cells in the phloem

Answer 9

Large nucleus
Dense cytoplasm
Lots of mitochondria
Carry out metabolic processes required by sieve tubes

Question 10

What are plasmodesmata

Answer 10

Gaps within cell walls that connect the cytoplasm of two adjacent cells

Question 11

What are the three pathways that water and minerals get to the xylem

Answer 11

Apoplast
Symplast
Vacuolar

Question 12

What is the Vacuolar pathway

Answer 12

Water enters through plasma membrane and passes through the plasmodesmata from one cell to the next
Can pass through the vacuoles

Question 13

What is the symplast pathway

Answer 13

Water enters through plasma membrane and passes through the plasmodesmata from one cell to the next

Question 14

What is the apoplast pathway

Answer 14

Water passes through spaces in the cell wall and between cells

Question 15

How is water moved from the outside to the xylem

Answer 15

Minerals are actively transported into the root hair cell - lowering w.p. Water then moves in through osmosis. It then follows three different pathways (down a wp grad). When it gets to the casparian strip, water is forced into the cytoplasm. Minerals are actively transported into xylem and water follows through osmosis. No leaks due to casparian strip

Question 16

What is transpiration

Answer 16

The process of water moving through a plant and it’s evaporation from aerial parts

Question 17

How does water move up the stem

Answer 17

root pressure
transpiration pull
capillary action

Question 18

What is root pressure

Answer 18

When osmosis is driven by minerals moving into cells by active transport
Gets water from outside to xylem
More water entering means more water will be pushed up the stem

Question 19

What is transpiration pull

Answer 19

Cohesion causes water molecules to be pulled up when water molecules evaporate as they stick together, this pull from above causes tension

Question 20

What is capillary action in plants

Answer 20

Adhesion causes water molecules to be attracted to the lignin
The narrowness of the xylem causes these forces of attraction to pull up water via the sides of the xylem

Question 21

How does water leave the leaf

Answer 21

Water moves from xylem to a spongy mesophyll cell via a pit
Water evaporates
Water vapour diffuses down a water vapour potential gradient across the airspace and out the stomata
Water vapour is taken away by air currents

Question 22

What steps should be taken when setting up a potometer

Answer 22

Cut shoot underwater
Make sure there are no air bubbles
Make sure shoot is healthy
Cut end off shoot

Question 23

Why does the plant use the transpiration stream

Answer 23

Photosynthesis
Growth
turgidity
mineral/ion transport
keeps plant cool

Question 24

What factors effect rate of transpiration

Answer 24

Number of leaves
Temperature
Features of stomata
Thickness of cuticle
Light
Humidity
Air movement
Water availability

Question 25

How does light effect the rate of transpiration

Answer 25

Opens stomata
Increases rate of photosynthesis

Question 26

How does temperature effect the rate of transpiration

Answer 26

Increase in KE
More evaporation from spongy mesophyll
increase rate of diffusion
decreases water vapour potential in air
increases water vapour potential gradient

Question 27

How does humidity effect the rate of transpiration

Answer 27

Higher humidity = less water loss
smaller water vapour potential gradient

Question 28

How does air movement effect the rate of transpiration

Answer 28

Carries away water vapour
Maintains a high water vapour gradient

Question 29

Why is transpiration unavoidable during the day?

Answer 29

Stomata have to be open to allow for gaseous exchange for photosynthesis

Question 30

What is the name of plants adapted to live in very dry or arid conditions

Answer 30

xerophytes

Question 31

What are the adaptations to reduce water loss

Answer 31

lose leaves in winter
smaller leaves (needles)
Densely packed spongy mesophyll
Thick waxy cuticle
Hairs on surface
Sunken stomata
Rolling leaves
High salt conc in cells

Question 32

Why does having densely packed spongy mesophyll reduce water loss

Answer 32

reduces SA exposed so less water evaporates into air spaces

Question 33

How does hairs on the surface of plants reduce water loss

Answer 33

Traps a layer of air that is saturated with water vapour
decreases water vapour potential gradient

Question 34

How does sunken stomata reduce water loss

Answer 34

Traps a pocket of air saturated with water vapour
reduces water vapour potential gradient

Question 35

How does rolling leaves reduce water loss

Answer 35

Traps a pocket of air saturated with water vapour
reduces water vapour potential gradient

Question 36

How does maintaining a high salt concentration in cells reduce water loss

Answer 36

Lowers water potential, means more water can enter through osmosis

Question 37

What are the features of marram grass

Answer 37

xerophytes
Thick waxy cuticle
rolled leaves
leaf hairs
sunken stomata

Question 38

Features of cacti

Answer 38

No or thin leaves
small surface area
stores water in stem
have shallow wide spreading leaves

Question 39

What are hydrophytes

Answer 39

Plants adapted to live in and on water

Question 40

What are feature of hydrophytes

Answer 40

Air spaces in leaves so they can float
Air spaces in roots and stem so O2 can move from leaves to underwater parts
Stomata on upper surface
Flexible leaves and stems

Question 41

What do companion cells contain

Answer 41

Many plasmodesmata
All major organelles
Many mitochondria

Question 42

What do sieve tubes contain

Answer 42

mitochondria
sieve plate

Question 43

What is translocation

Answer 43

Movement of assimilates from source to sink
Sugars in the form of sucrose are transported via phloem

Question 44

How does the process of translocation occur

Answer 44

H+ are actively moved from companion cell to source cell by proton pump
H+ move back into companion cells down a conc grad through the H+ sucrose cotransporter - this means sucrose is moved in too
Conc of sucrose builds up in companion cell, this means it will diffuse down a concentration gradient into phloem via plasmodesmata
water potential in phloem decreases so water moves into phloem from xylem by osmosis
this causes an increase in hydrostatic pressure
Water moves down xylem to a lower hydrostatic pressure at sink, this carries assimilates with it

Question 45

What are some differences between the xylem and phloem

Answer 45

Xylem has no cytoplasm, Phloem does
Xylem is lignified, phloem isn’t
Xylem has bordered pits, phloem doesn’t