Question

What are 3 limiting factors of photosynthesis?

Answer 1

Limiting factors of photosynthesis: The various factors which affect the rate of photosynthesis are:

1. Light
   1. Incident light is directly proportional to CO₂ fixation rate, but at the higher light intensities, its rate does not increase further as other factors become limiting.
   2. Light is also rarely a limiting factor (with the exception of shade plants or plants of the dense forest) as light saturation occurs at 10% of the full sunlight.
   3. Beyond a point, if the incident light is increased, it leads to a decrease in photosynthesis due to the breakdown of chlorophyll.
2. CO₂ Concentration
   1. Major limiting factor
   2. Usually low in the atmosphere (0.03 − 0.04%), Up to 0.05% − increases rate of CO₂ fixation, > 0.05% − damaging effect.
   3. Though both the C₃ and C₄ show an increase in the rate of photosynthesis at high light intensity accompanied by high CO₂ concentration, This saturation point for the C₃ is obtained at higher concentrations as compared to the C_4. Therefore, CO₂ concentration is more of a limiting factor for C₃ plants.
   4. Increased CO₂ concentration is also beneficial for greenhouse crops such as tomatoes and bell paper.
3. Temperature
   1. Dark reactions are more sensitive to an increase in temperature.
   2. C4 plants respond more to an increase in temperature as compared to C₃ plants.
   3. Adaptations according to a habitat also affect the temperature optima.
   4. Tropical plants generally have higher temperatures compared to temperate ones.