Limiting factors – Anything that will limit the rate of photosynthesis.
- No light = no photosynthesis (exchange of gas can’t physically occur as the stomata do not open in dim conditions)
- As light level increase, so does the rate of photosynthesis, as the stomata open to allow the exchange of gasses
- However there will come a point when there is no corresponding increase to the rate of photosynthesis, because another factor will become rate limiting.
- During the day (the point of highest temperature and light intensity for maximum kinetic energy therefore the fastest point at which photosynthesis can occur), A leaf has to exchange a large volume of air – as air only contains 0.04% of carbon dioxide, it needs enough to pacify sufficient amounts of CO2 into the chloroplasts of leaves.
- Like CO2 concentration, there will come a point when there is no corresponding increase to the rate of photosynthesis, because another factor will become rate limiting.
- Generally enzymes work faster at warmer temperatures. At optimum temp, the photosynthetic enzymes and substrate molecules collide faster, increasing the rate of photosynthesis.
- However, if the temperature is too hot, enzymes will denature and the rate of photosynthesis will decline, hence the fall in the graph.
Another rate limiting factor of photosynthesis is transpiration rate; however as transpiration rate is described in more detail in another post, feel free to browse the other posting 🙂