Practice Questions

1.List three ways the rate of photosynthesis can be measured

1.Amount of oxygen produced per minute

2. Amount of carbon dioxide used per minute

3. Change in biomass per unit time. 

2.A plant is kept in low light but high carbon dioxide and optimal temperature. Which factor is limiting photosynthesis and why?

Light intensity is the limiting factor.

Reason: Even though carbon dioxide and temperature are at optimal levels, photosynthesis cannot occur faster than the plant can absorb light. Light provides the energy for the reaction, so when it is low, it restricts the rate of photosynthesis. Increasing light intensity would increase the rate until another factor becomes limiting.

3.During a sunny day, a plant shows no further increase in photosynthesis despite more sunlight. Suggest possible limiting factors.

If a plant no longer increases its rate of photosynthesis despite more sunlight, this means light is no longer the limiting factor. Other factors could now be limiting, such as:

Carbon dioxide concentration – there may not be enough CO₂ for the plant to increase photosynthesis further.

Temperature – if the temperature is too low or too high, enzymes controlling photosynthesis may slow down or denature.

Amount of chlorophyll – if the plant has a low chlorophyll content, it cannot absorb more light even if light intensity increases.