Read Net Photosynthesis as CO2 Balance
Read photosynthesis questions as a net CO₂ balance: carbon uptake by photosynthesis minus carbon release by respiration.
Photosynthesis uses light energy to make food in green plant cells; transport tissues move water and sugar where they are needed.
Track what enters, leaves and moves inside
H₂O rises from roots in xylem · sugar travels from the leaf in phloem
CO₂ enters through stomata; water arrives from roots; oxygen leaves the leaf. Sugar moves from the source leaf to use or storage sites.
Read the hydrogen-carbonate indicator
Respiration adds CO₂ and lowers pH, so an unlit leaf turns the indicator yellow. In dim light, CO₂ uptake and release can balance, leaving cherry red. In full light, net CO₂ uptake raises pH and turns the indicator purple. The sequence is yellow, cherry red, purple: choose B.
Find the largest net gap
Net photosynthesis is not the peak of the photosynthesis curve. It is the vertical gap between gross CO₂ uptake and respiration. In the temperature graph, that gap is largest before respiration rises strongly, in the 10–20°C range. Choose A.
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- ✓Darkness: respiration dominates and CO₂ rises.
- ✓At the compensation point, photosynthesis and respiration balance.
- ✓Net photosynthesis equals gross photosynthesis minus respiration.
Do not select the peak of gross photosynthesis when the question asks for net photosynthesis.
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