What factors affecting photosynthesis?
The various factors that affect rate of photosynthesis are:
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Light
- Incident light ∝ CO 2 fixation rate; but at higher light intensities, the rate does not increase further as other factors become limiting
- Light is rarely a limiting factor (with exception of the shade plants or plants of dense forest) because light saturation occurs at 10% of the full sunlight.
- Beyond a point, if incident light is increased, then it leads to decrease in photosynthesis due to breakdown of chlorophyll.
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CO 2 Concentration
- Major limiting factor
- Usually low in atmosphere (0.03 − 0.04%)
- Up to 0.05% − increases rate of CO 2 fixation
- > 0.05% − damaging effect
- Though both C 3 and C 4 show increase in rate of photosynthesis at high light intensity accompanied by high CO 2 concentration, the saturation point for C 3 is obtained at higher concentrations as compared to C 4 . Therefore, CO 2 concentration is more of a limiting factor for C 3 plants.
- Increased CO 2 concentration is beneficial for greenhouse crops such as tomatoes and bell paper.
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Temperature
- Dark reactions are more sensitive to an increase in temperature.
- C 4 plants respond more to an increase in temperature as compared to C 3 plants.
- Adaptations according to habitat also effect temperature optima. Tropical plants have higher temperature optima compared to temperate.
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Water
- Water stress causes stomata to close and hence, less CO 2 is available.
- Water stress causes the leaves to wilt, thereby reducing their surface area and metabolic activity as well.