Plants

Question 1

What does ringing show?

Answer 1

That the phloem is responsible for translocation

Question 2

How does ringing work?

Answer 2

Cut around the circumference of the tree, cut away the bark and phloem.
Accumulation of liquid above cut is sugars.
Tissue below dies as respiration is cutting off with no glucose.

Question 3

What is transpiration?

Answer 3

The loss of water vapour from the stomata by the process of evaporation.

Question 4

What factors affect transpiration?

Answer 4

Light intensity.
Wind.
Humidity.
Temperature.

Question 5

How does temperature affect transpiration?

Answer 5

The higher the temp, the more kinetic energy, the more transpiration occurs.

Question 6

Effect of humidity on transpiration?

Answer 6

Water vapour outside the plant is trapped.
This reduces the water potential gradient. Less transpiration occurs.

Question 7

Effect of wind on transpiration?

Answer 7

Wind blows away humid air. Water potential gradient is maintained. Transpiration occurs.

Question 8

Effect of light intensity on transpiration?

Answer 8

Increased light leads to increased transpiration as the stomata opens creating a larger surface area for water loss.

Question 9

How does cohesion tension theory work?

Answer 9

Water molecules have cohesion.
Adhere to the xylem wall.
Creates a continuous column that is pulled upwards.
Tension is caused by transpiration as water is lost.

Question 10

Function of the waxy cuticle

Answer 10

Protects the surface of the leaf. Prevents water loss

Question 11

Function of the thin upper epidermis

Answer 11

Allows light to reach the palisade cells.

Question 12

Function of the palisade cells

Answer 12

Contain chlorophyll for photosynthesis

Question 13

Function of the spongy mesophyll

Answer 13

Air spaces allow for diffusion of gases

Question 14

Function of the guard cells

Answer 14

Open and close the stomata.

Question 15

What do guard cells do to open the stomata?

Answer 15

Swell

Question 16

What do guard cells do to close the stomata?

Answer 16

Shrink

Question 17

Function of the stomata

Answer 17

Allows for gas exchange. Controls water loss.

Question 18

Function of the xylem

Answer 18

Transpiration stream of water

Question 19

Function of the phloem

Answer 19

Transports sucrose around the plant via translocation

Question 20

What are xerophytes?

Answer 20

Plants adapted to live in areas where water is in limited supply

Question 21

Adaptations of xerophytes?

Answer 21

Reduced surface area
Waxy cuticle
Rolled leaves
Hairy leaves
Stomata in pits and grooves

Question 22

Why is reduction of surface area good for xerophytes?

Answer 22

Small leaves reduce SA.
Curled leaves reduce evaporation.
E.g. cactus

Question 23

Why is a thick waxy cuticle good for xerophytes?

Answer 23

Less water loss.
E.g. holly

Question 24

Why are rolled leaves good for xerophytes?

Answer 24

It protects the lower epidermis from the outside. Traps water vapour so less water is lost.
E.g. marram grass

Question 25

Why are hairy leaves good for xerophytes?

Answer 25

Traps moist air. Decreases gradient so less water is lost. E.g. heather

Question 26

Why is is good for xerophytes to have stomata in pits and grooves?

Answer 26

Reduces transpiration as moist air is trapped. E.g. pine trees

Question 27

When is oxygen diffusion at its highest rate in a plant?

Answer 27

At night

Question 28

How does tracing work?

Answer 28

Plants are placed in a radioactive isotopes environment where they photosynthesise sugar. Place plant stems on x ray film. Where areas are blackened on the film is where the phloem is as the isotope is in the sugar

Question 29

What isotope is used in tracing?

Answer 29

14 C

Question 30

Steps in translocation

Answer 30

Load sucrose via active transport from source. Lowers water potential. Water moves in via osmosis from xylem. Creates a high hydrostatic pressure. Sucrose moves down gradient. Sucrose unloads via diffusion to sink. Increases water potential. Water leaves via osmosis back to the xylem.