Transport in plants

Question 1

Why do plants require water?

Answer 1

● Photosynthesis
● Maintenance of structure (turgidity)
● Cooling effect

Question 2

Why do plants require mineral ions?

Answer 2

For growth e.g. nitrates are required to

produce proteins

Question 3

Which structure in plants is adapted for the uptake of

water and minerals?

Answer 3

Root hairs

Question 4

How is water transported into root hairs?

Answer 4

● Lower concentration of water in root hair cells
than in the soil
● Water diffuses down its concentration gradient
into root hair cells by osmosis

Question 5

How are minerals transported into root hairs?

Answer 5

● Lower concentration of mineral ions in the soil
than in the root
● Root hair cells take up mineral ions by active
transport

Question 6

Outline how plant roots are adapted for the

absorption of water and minerals

Answer 6

Plant roots are composed of millions of root hair cells which have:
● Long hairs that extend from the cell body, increasing the
surface area for absorption
● Many mitochondria which produce ATP for active transport of
mineral ions

Question 7

Name the two plant transport tissues

Answer 7

Xylem

Phloem

Question 8

What is the function of the xylem?

Answer 8

Transports water and dissolved mineral ions up the
plant, from the roots to the leaves via the
transpiration stream

Question 9

Describe how the xylem is adapted to its function

Answer 9

• Hollow dead cells (no cytoplasm).
• Cells walls at the end broken
down (perforated end plates) so one long tube is
formed.
• Has lignin to make it strong to
support the plant and not burst.
• Is waterproof but has pits so
water can only get out through these.

Question 10

What is the function of the phloem?

Answer 10

Transports sucrose up and down the stem
from photosynthetic tissues (e.g. mature
green leaves) to non-photosynthetic tissues
(e.g. developing seeds) via translocation

Question 11

What are the two cell types that make up the

phloem?

Answer 11

Sieve tube elements

Companion cells

Question 12

Describe how the phloem is adapted to its function

Answer 12

• Sieve cells have little cytoplasm so it is easy for substances to pass though.
• Cell wall at each end has holes in to allow sucrose to move through.
• Has companion cells attached to it. These have many mitochondria to release energy. This is used to actively transport the sucrose into the phloem.

Question 13

What is transpiration?

Answer 13

The loss of water vapour from the parts
of a plant exposed to the air due to
evaporation and diffusion

Question 14

Where does the majority of transpiration take place?

Answer 14

Leaves

Question 15

Describe the process of transpiration

Answer 15

● Water evaporates from the mesophyll cell surfaces and diffuses
out of the stomata
● Water molecules (which have cohesive properties) are drawn
up the xylem vessels to replace the water that has been lost
● This causes more water molecules to be absorbed from the soil
into root hair cells

Question 16

How does the transpiration stream transport mineral ions?

Answer 16

Mineral ions are dissolved in the water

that is carried by the transpiration stream

Question 17

What are stomata?

Answer 17

They are pores found in the lower
epidermis of a leaf which allow gas
exchange

Question 18

What are guard cells?

Answer 18

Specialised cells surrounding the stoma
that change shape to control the size of
the pore

Question 19

How do guard cells control the size of stomata?

Answer 19

To open the stomata:
Water enters guard cells by osmosis. They swell and become turgid. They bend
and draw away from each other, opening the stomata.

To close the stomata:
Water leaves guard cells. They become flaccid, closing the
stomata.

Question 20

What factors affect the rate of transpiration?

Answer 20

● Light intensity
● Temperature
● Air movement

Question 21

Describe how high light intensity affects the rate of

transpiration

Answer 21

● High light intensity, greater number of stomata open to allow gas
exchange for photosynthesis

● Rate of photosynthesis increases so more water is taken up from the
soil, pushing water up the xylem

● More water vapour diffuses out of the stomata
∴ rate of transpiration increases

Question 22

Describe how low light intensity affects the rate of

transpiration

Answer 22

At a low light intensity, fewer stomata are
open so the rate of transpiration
decreases.

Question 23

Describe how temperature affects the rate of

transpiration

Answer 23

● Temperature increases, water molecules have more KE so rate of
diffusion increases
● Photosynthesis also increases so more water is taken up from the
soil, pushing water up the xylem
● More water vapour diffuses out of the stomata
∴ rate of transpiration increases

Question 24

Describe how air movement affects the rate of

transpiration

Answer 24

● Air movement increases, high water concentration gradient
maintained between the air spaces in the leaf and atmosphere
● Increased rate of diffusion of water molecules out of the
stomata
● Rate of transpiration increases

Question 25

What apparatus is used to measure the rate of

transpiration?

Answer 25

Potometer

Question 26

What is assumed when measuring the rate of

transpiration using a potometer?

Answer 26

rate of water uptake ≈ rate of transpiration

Question 27

How can the rate of transpiration be calculated using

a potometer?

Answer 27

rate of transpiration = distance moved by bubble/ time taken

Question 28

What is translocation?

Answer 28

The movement of sugars (sucrose,
amino acids etc.) up and down a plant,
from the source to the sink, via the
phloem, this requires ATP.

Question 29

Identify the structures of the leaf labelled

in the diagram below

Answer 29

https://www.physicsandmathstutor.com/pdf-pages/?pdf=https%3A%2F%2Fpmt.physicsandmathstutor.com%2Fdownload%2FBiology%2FGCSE%2FNotes%2FEdexcel%2F6-Plant-Structures-and-their-Functions%2FFlashcards%2FFlashcards%2520-%2520Topic%25206%2520Transport%2520in%2520plants%2520-%2520Edexcel%2520Biology%2520GCSE.pdf

page 58

Question 30

Describe how leaves are adapted for

photosynthesis

Answer 30

● Broad - large surface area for light absorption
● Thin - short diffusion distance for gases, allows light to reach all cells
● Vascular bundles (xylem and phloem) form a network to deliver
water and remove glucose.Also provide support.
● Photosynthetic pigments (e.g. chlorophyll) absorb light

Question 31

Describe how tissues of the leaves are adapted for photosynthesis and gas exchange

Answer 31

● Palisade mesophyll layer - receives most light so contains greatest
concentration of chloroplasts
● Upper epidermis - transparent, allows light to reach palisade layer
● Spongy mesophyll layer - air spaces increase the rate of diffusion
● Lower epidermis - contains many stomata for gas exchange

Question 32

Describe how plants are adapted to live in hot, dry conditions

Answer 32

● Small leaves/spines - reduce surface area for water loss

● Thick waxy cuticle - reduces evaporation, conserving water

● Thick stem - provides a storage of water

● Shallow but widespread roots - large surface area to absorb water

● Stomata sunken in pits and leaves curled - reduces airflow, lowering
diffusion gradient and reducing water loss by evaporation

● Stomata close to reduce water loss

Question 33

_____________ are used to produce proteins.

Answer 33

Nitrates

Question 34

Describe how plants are adapted to live in cold conditions

Answer 34

• Deciduous trees with broad leaves lose their leaves in the winter. This prevents water loss when soil might be frozen.
• Most conifers though (e.g. pine trees) don’t do this. Instead they have needle shaped leaves with a much smaller surface area and very thick cuticles.
• Plants can also reduce water loss by trapping water vapour close to their leaves. This slows down the rate of diffusion out of the stomata. Broad leave plants often have their stomata in sunken pits. This allows them to fill with water to slow diffusion further.