Limiting factors of photosynthesis

Temperature

The light independent stage of photosynthesis is effected much more than the light dependent stage
Between 0 and 25 degress an increase of 10 degress will see the rate of photosynthesis double
Tempererature initiallly stops limiting photosynthesis at tempereratures over 25 degrees
At higher tempereratures the following occurs to reduce photosynthesis
- Enzymes work less effectively
- Oxygen becomes more effective at competing for the rubisco active site, blocking off carbon dioxide
- More water is lost through the stomata causing a stress response leading the stomata closing. This means less carbon dioxide can be uptaken.

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Higher levels of carbon dioxide can potentially increase the rate of photosynthesis
Carbon dioxide is used in the Calvin Cycle
It is essential for fixing the enzyme rubisco
The atmosphere contains between 0.03%-0.06% of carbon dioxide
Growing plants produce carbon dioxide at a higher rate than they release it in respiriation however, mature plants have an equal production:release rate
In greenhouses the concentration can drop to around 0.02%- this is counteracted by burning methane or oil heated fires.

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As light intensity increases the rate of photosynthesis increases
Light has three main effects on plants that affects photosynthesis
- Stomata are forced to open so carbon dioxide can enter leaves
  - This is essential for the Calvin Cycle
- It is trapped by chlorophyll where it excites electrons
- It splits water molecules to produce protons
  - Essential to the light dependent stage
- These electrons and protons are used in photophosphorylation which produces ATP
  - ATP is essential for the fixation of carbon dioxide and the change from GP to TP and TP to RuBP
Light affects the rate of photosynthesis by acting on the levels of the light dependent and independent stages
The overall rate of photosynthesis varies throughout the day as the light intensity increases and decreases

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