2.44B: Understand How Respiration Continues during the Day and Night, but that the Net Exchange of Carbon Dioxide and Oxygen Depends on the Intensity of Light

*PROCESSES OCCURRING DURING THE DAY

• Plants respire during both the daytime and night-time, but can only conduct photosynthesis during the daytime in the presence of light

PROCESS	DAY	NIGHT
RESPIRATION	✓	✓
PHOTOSYNTHESIS	✓	✗

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*NET GAS EXCHANGE DURING THE DAY

DAYTIME

Diagram showing the Net Exchange of Gases during the Daytime

As Respiration occurs at all times of day, respiring cells of plants will take in Oxygen to respire and produce waste products of Carbon Dioxide and Water vapour that will be released from the plant However, as Photosynthesis occurs during the daytime under the presence of light, photosynthesising cells (chloroplasts) will take in Carbon Dioxide to photosynthesise and produce waste products of Oxygen and Water vapour that will be released through the Stomata Hence, as Oxygen is both taken in and released by the plant (by respiration and photosynthesis), and Carbon Dioxide is both released and taken in by the plant (by respiration and photosynthesis), the net exchange of gases is balanced during the daytime

NIGHT-TIME

Diagram showing the Net Exchange of Gases during the Night

As Respiration occurs at all times of day, respiring cells of plants will take in Oxygen to respire and product waste products of Carbon Dioxide and Water vapour that will be released from the plant However, as Photosynthesis does not occur during the night-time due to the absence of light, photosynthesis will not occur Hence, as Oxygen is taken in for respiration but not produced (by photosynthesis), the net exchange of Oxygen will have an increase input Additionally, as Carbon Dioxide is produced by respiration but not taken in (by photosynthesis), the net exchange of Carbon Dioxide will have an increased output