Transpiration

Question 1

What is transpiration?

Answer 1

The result of evaporation of water vapour from the stomata of leaves

Question 2

What does transpiration do?

Answer 2

It delivers water and dissolved mineral ions around the plant

Question 3

What is the importance of water loss?

Answer 3

Water loss via stomata is key for movement through the plant in the transpiration stream

Question 4

What are parts of the leaf?

Answer 4

Large SA, waxy cuticle, stomata and guard cells

Question 5

What is the function of the large SA?

Answer 5

Captures light for photosynthesis and many stomata for gas exchange

Question 6

What is the function of the waxy cuticle?

Answer 6

It prevents leaf cells from losing water constantly by evaporation from surface

Question 7

What is the function of stomata?

Answer 7

Carbon dioxide an oxygen out of microscopic pores on underside of leaf and water vapour evaporation

Question 8

What is the function of guard cells?

Answer 8

Surround stomata and open and close them to control water loss but allow gas exchange

Question 9

How do stomata control rate of transpiration?

Answer 9

By opening and closing stomata pores by the guard cells

Question 10

What is structure of the guard cells?

Answer 10

Thin outer and thin inner walls

Question 11

How does the pore open?

Answer 11

1. In favourable water contains, solutes are pumped by active transport.
2. Water follows by osmosis.
3. Turgor increases
4. Cellulose hoops prevent cell swelling.
5. Inner wall is less flexible
6. Cell changes to bean shape
7. Pore opens

Question 12

What happens when it’s dark?

Answer 12

Photosynthesis cannot occur as it requires light energy but respiration is still occurring so oxygen is used up and carbon dioxide diffuse out of plant

Question 13

What is the compensation point?

Answer 13

The point where carbon dioxide being taken up by the plant is equal to the carbon dioxide being released because of cellular respiration

Question 14

How does water move from xylem to stomata?

Answer 14

1. Osmosis from xylem to mesophyll cell cytoplasm (symplast)
2. Diffusion from xylem through mesophyll cell walls and intracellular spaces (apoplast)
3. Evaporation from mesophyll cellulose cell walls into mesophyll air spaces.
4. Diffusion of water vapour from the mesophyll air spaces out through stomata

Question 15

What is capillary action?

Answer 15

Water rising up in a narrow tube

Question 16

What causes capillary action?

Answer 16

The adhesion and cohesion of water in xylem

Question 17

What is transpiration pull?

Answer 17

Evaporation of water from the stomata in the leaves pulls a column of water through the plant from roots to the leaves

Question 18

What is the result of transpiration pull?

Answer 18

Tension in the xylem which helps to move water across the roots from the soil

Question 19

What is the result of thick lignified walls?

Answer 19

Prevents the collapse under the tension that develops during transpiration and pits between xylem vessels elements allow unbroken columns of water

Question 20

What is evidence of transpiration pull?

Answer 20

Tree trunk diameter which changes over the day and cut up flowers of stems where air is drawn into xylem rather than water leaking out and water stops moving up stem

Question 21

Why does the tree trunk diameter get smaller?

Answer 21

The tension from water being pulled up pulls xylem vessel walls in