B7.1

Question 1

What is the functions of: xylem

Answer 1

Transport water + minerals from roots -> stem, shoot, leaves

Only goes one direction

Cells are dead -> contain lignin (protein) to make walls (they also support the plant)

No end wall -> one long hollow tube -> old cell walls have broken down

No cytoplasm or nuclei, just water in tube

Question 2

What is the function of: phloem

Answer 2

Transports sugar in leaves through the plant
-> rest of leaves
-> stem -> growing and storage tissue

Living cells -> sieve tubes -> small holes in cell wall -> flow between cells

Cytoplasm but no nuclei
End of cell wall -> sieve plate

Question 3

What is a vascular bundle?

Answer 3

Two tubes found closely together:
Xylem and phloem -> main transport in plants

Question 4

What is the location of the vascular bundle in:
Leaves
Stems
Roots

Answer 4

Leaves:
One on top of the other
Many small sections together

Stem:
Multiple pill-like shapes in a circle
Phloem outside, xylem inside

Root:
Xylem -> rounded cross in the middle
Phloem -> dots in the pockets of the cross

Question 5

What are root hair cells?

Answer 5

They are single cell extensions of epidermis cells in root

Grow between soil particles to absorb water and minerals

Water enters via osmosis -> soil has higher water potential than cytoplasm

Question 6

What do root hair cells look like under a light microscope?

Answer 6

A long tube coming from the root

Question 7

How do root hair cells help increase the absorption of water?

Answer 7

Increase surface area -> increased rate of absorption and active transport

Question 8

What is active transport?

Answer 8

Since the mineral concentration is lower in the soil, the plant uses:

Uses ATP energy
Root hair cells have specialised channel to take in minerals from the soil

Carrier protein moved mineral into plant across concentration gradient
Mineral ions transported into the xylem

Question 9

Describe the pathway of water from the soil to the mesophyll cells

Answer 9

Osmosis cause water to pass into the root hair cell -> root cortex cells -> xylem -> leaf mesophyll cells

Question 10

Describe an experiment that can show the pathway of water using appropriate stains

Answer 10

Experiment:
- Place plant (in this case celery) into beaker of water with a stain (food coloring)
- after few hours -> leaves of the celery are the same color as the stain

Shows water is taken up by the celery

Cross section:
If celery cut -> only certain areas would be stained -> water is being carried through specific vessel -> xylem vessels

Question 11

What is transpiration?

Answer 11

The loss of water vapor from leaves -> evaporation of water at the surface of mesophyll cells followed by diffusion of water vapor through stomata

Question 12

What are the functions of transpiration?

Answer 12

Transporting mineral ions

Providing water to keep cells turgid -> support plant

Providing water to leaf cells for photosynthesis

Keeping leaves cool (evaporation requires heat energy)

Question 13

How does water move up the xylem vessel?

Answer 13

Transpiration pull:
- Water molecules attracted to each other (cohesion) -> continuous column of water up
- transpiration produces tension/pull on the water
- cohesive force keeps the stream going (each molecules pull on the one under it)

Increased rate of transpiration -> increased rate of water being pulled up

Question 14

What is cohesion?

Answer 14

Particles of the same type are attracted to each other and stick together

Question 15

What is adhesion?

Answer 15

Particles are attracted to other objects and stick to other things

Question 16

How does the water potential gradient help transpiration (transpiration mechanism pt.2)?

Answer 16

Leaves have the lowest water potential -> caused by loss of water vapor by transpiration
Air spaces in leaves -> large surface area of wet cells -> increased rate of evaporation
Stomata open -> water vapor diffuse out -> more water evaporates

Root -> absorption of lot of water (helped by root hair cells)
Xylem provides easy pathway for water

High concentration in root and low concentration in leaves encourage movement of water to areas of lower concentration

Question 17

Describe stomata movement

Answer 17

Underside of leaves -> holes called stomata (sing. Stoma)

Surrounded by 2 guard cells -> control opening and closing

CO2 low -> guard cells gain water and become turgid -> curves out
Allows gases in and out (because of concentration gradients), evaporates water

CO2 high-> guard cells lose water (evaporation) -> flaccid -> closes stomata
Also caused by low water levels -> prevent water loss

Question 18

Describe an experiment that shows the effects of variation in heat and humidity on transpiration rates

Answer 18

Experiment:
1. Cut shoot underwater at an angle (prevent air entering xylem) place in tube

2. Set up apparatus (see notes) and make sure it is air and water tight
3. Dry the leaves of the shoot
4. Remove the capillary tube from the beaker of water and allow a single air bubble to form
5. Place the tube back into the water
6. Set factors
7. Allow plant to adapt for 5 min
8. Record the starting position of the air bubble and leave for a set period of time
9. After time record the position of the bubble

10: rinse and repeat to test other factors or variations

Variables:
Independent -> wind speed/temp
Dependent -> rate of transpiration
Control -> light, temp, wind speed, type of plant, surface area of leaves

Question 19

What happens if there is too much transpiration?

Answer 19

Water evaporating > water available in the soil moving into the root via osmosis -> results in wilting

Cells are not full of water -> strength of cell wall cannot support plant -> collapse

Question 20

What is the rate of transpiration?

Answer 20

The speed at which the plant loses water

Question 21

How does variation in light intensity effect transpiration rates?

Answer 21

Rate of transpiration increase as light intensity increases

When sunny -> increased photosynthesis, plant uses more H2O and CO2

Stomata is open -> CO2 in and water evaporates out

Question 22

How does variation in temp effect transpiration rates?

Answer 22

Rate of transpiration increases as temp increases

Higher temp -> heat leaves -> water evaporates quicker

Warm air absorbs more water vapor than cold air

Question 23

How does variation in air movement/wind effect transpiration rates?

Answer 23

Rate of transpiration increases as wind increases

Saturated air replaced with dry air quicker

Water concentration in air is consistently lower -> increased rates of transpiration -> water potential gradient is more exaggerated

Question 24

How does variation in humidity effect transpiration rates?

Answer 24

Rate of transpiration decreases as humidity increases

Humid -> already pretty saturated air -> water potential gradient is less exaggerated

Question 25

What is translocation?

Answer 25

The movement of sucrose and amino acids in the phloem from regions of production (source) to regions of storage, utilisation or growth (sink)

Question 26

Where do the phloem tubes transport the amino acids and sucrose?

Answer 26

Winter -> plants have no leaves -> transports from storage organs to other parts of the plant for respiration

Growth period (usually spring) -> storage organs would be the source, and the growing areas of the plant are the sinks

Summer -> plant has grown -> leaves are photosynthesizing and producing lots of sugars -> leaves are source and root are sinks -> stores sucrose as starch until needed

Question 27

What is sucrose?

Answer 27

Glucose and fructose (fructose is used in nectar and flower use sucrose -> fructose)