6.4- GAS EXCHANGE IN THE LEAF OF A PLANT

Question 1

What do all plant cells require during respiration and what do they produce?

Answer 1

require oxygen

produce carbon dioxide

Question 2

What do plants cells take in during photosynthesis and what do they produce?

Answer 2

take in carbon dioxide

produce oxygen

Question 3

When photosynthesis is happening where does some of the carbon dioxide come from?

Answer 3

respiration of cells

Question 4

Where is most of the carbon dioxide for photosynthesis obtained?

Answer 4

from external air

Question 5

For respiration in plants where does some of the oxygen come from?

Answer 5

some oxygen from photosynthesis

Question 6

What happens to most of the oxygen produced from photosynthesis?

Answer 6

most of it diffuses out of plant

Question 7

Example of when photosynthesis is not occuring?

Answer 7

in the dark

Question 8

What does oxygen do when photosynthesis is not occuring?

Answer 8

oxygen diffuses into the leaf

Question 9

Why does oxygen diffuse into the leaf when photosynthesis is not occurring?

Answer 9

as it’s constantly being used by cells during respiration

Question 10

What happens to carbon dioxide produced from respiration?

Answer 10

diffuses out

Question 11

How is gas exchange in plants similar to that of insects?

Answer 11

no living cell far from external air- so source of oxygen + carbon dioxide

diffusion happens in gas phase (air), which makes it more rapid than if it were in water

Question 12

What is the diffusion pathway like in plants?

Answer 12

short, fast diffusion pathway

Question 13

What do the air spaces inside a leaf have?

Answer 13

large SA compared with volume of living tissue

Question 14

Is there a specific transport system for gases?

Answer 14

no- simply move in + through plant by diffusion

Question 15

Where does most gaseous exchange happen in plants?

Answer 15

occur in leaves

Question 16

What adaptations do leaves have for rapid diffusion? (3)

Answer 16

many small pores, called stomata

numerous interconnecting air-spaces that occur throughout mesophyll

large SA of mesophyll cells

Question 17

How is many small pores, called stomata an adaptation of leaves for rapid diffusion?

Answer 17

so no cell far from stoma + so diffusion pathway short

Question 18

How is numerous interconnecting air-spaces that occur throughout mesophyll an adaptation of leaves for rapid diffusion?

Answer 18

so gases can readily come in contact with mesophyll cells

Question 19

How is large SA of mesophyll cells an adaptation of leaves for rapid diffusion?

Answer 19

for rapid diffusion

Question 20

What are stomata?

Answer 20

minute pores

Question 21

Where do stomata occur?

Answer 21

occur mainly, but not exclusively on leaves, especially on underside

Question 22

What is each stoma surrounded by?

Answer 22

pair of special cells (guard cells)

Question 23

What can the guard cells do to the stomatal pore?

Answer 23

can open or close stomatal pore

Question 24

What can the guard cells control as they can open/close the stomatal pore?

Answer 24

can control rate of gaseous exchange

Question 25

Why is it important that the guard cells can control the rate of gaseous exchange?

Answer 25

as terrestrial organisms lose water by evaporation

Question 26

How have plants evolved to balance the conflicting needs of gas exchange + control of water loss?

Answer 26

by closing stomata at time when water loss would be excessive