What is the relationship between the rate of photosynthesis and either the light intensity or the carbon dioxide concentration?

What is the relationship between the rate of photosynthesis and either the light intensity or the carbon dioxide concentration?

• A. The rate remains constant
• B. As light increases, the rate increases but not for CO2
• C. As either increases the rate of photosynthesis increases
• D. Increases for CO2 but not for light

Answer: (C)

The rate of photosynthesis depends on two main inputs: light energy and carbon dioxide. Light provides the energy for the light-dependent reactions, while CO2 is the carbon source for the Calvin cycle. If light is the limiting factor, increasing light raises the rate because more energy is available to drive the reactions. If CO2 is limiting, increasing CO2 raises the rate because more substrate is available for carbon fixation. In both cases, the rate goes up until another factor (such as enzyme capacity, pigment availability, or temperature) becomes the new limiting factor. So, increasing either light intensity or CO2 concentration tends to increase the rate of photosynthesis.

The rate of photosynthesis depends on two main inputs: light energy and carbon dioxide. Light provides the energy for the light-dependent reactions, while CO2 is the carbon source for the Calvin cycle. If light is the limiting factor, increasing light raises the rate because more energy is available to drive the reactions. If CO2 is limiting, increasing CO2 raises the rate because more substrate is available for carbon fixation. In both cases, the rate goes up until another factor (such as enzyme capacity, pigment availability, or temperature) becomes the new limiting factor. So, increasing either light intensity or CO2 concentration tends to increase the rate of photosynthesis.