Gas Exchange in Plants

Question 1

What diffusion happens in plants?

Answer 1

• plant photosynthesises, using lots CO2, hardly any in leaf
• CO2 moves into leaf by diffusion (area high conc. to low)
• O2 made as waste product in photosynthesis, some is used in respiration & rest diffuses out stomata (area high conc. to low)

Question 2

How are the stomata adapted for gas exchange?

Answer 2

• let gases diffuse in/out
• allows water to escape by transpiration
• close when water supplies are low to stop roots drying out, although it stops photosynthesis, plant drying out would be worse
• close when dark - water can’t escape out - doesn’t dry out

Question 3

How are plant’s broad leaves adapted for gas exchange?

Answer 3

large surface area for diffusion

Question 4

How are plant’s thin leaves adapted for gas exchange?

Answer 4

short distance to travel for gas exchange

Question 5

How are plant’s air spaces leaves adapted for gas exchange?

Answer 5

• lets gases move easily between cells
• increases surface area for gas exchange

Question 6

What does net exchange of gases depend on?

Answer 6

light intensity

Question 7

What net exchange of gases happen in plants?

Answer 7

• photosynthesis only happens in day (lots of light)
• plants respire all the time to get energy to live
• during day, plants make more oxygen by photosynthesis than they use in respiration
• in daylight, they release oxygen
• use more CO2 than they can produce, so take it in
• at night plants only respire (take in light), so take in oxygen & release CO2 (like humans)