Gas exchange and light

Respiration and light intensity

Respiration and light intensity

Plants respire at the same rate all the time.

• The rate of respiration is NOT dependent on light intensity.

• CO2 is released at the same rate all day/night.

Photosynthesis and light intensity

• The rate of photosynthesis increases with light intensity.

• Most of the O2 is released during the daytime.

• Photosynthesis doesn’t occur at night.

Gas exchange in the day

• Respiration taking place.

• O2 used by plant cells and CO2 released.

• Photosynthesis taking place.

Net concentration of CO2 and O2 during the day

• MORE O2 being released than used up.

• Net concentration of O2 increases.

• LESS CO2 being released than used up.

• Net concentration of CO2 decreases.

Gas exchange during the night

• Respiration taking place.

• O2 being used by plant cells, and CO2 released.

• Photosynthesis taking place.

Net concentration of CO2 and O2 during the night

• No O2 produced.

• Net concentration of CO2 increases.