Limiting Factors & CO2 Enrichment Experiments

• 3 limiting factors impact the rate of photosynthesis

  • light intensity (brightness)

  • CO2 concentration

  • temperature

Light Intensity:

• graph initially increases, then plateaus

• initially, there’s an increase in light intensity —> increase in the rate of photosynthesis

• eventually, maximum rate (Vmax) is reached and the rate plateaus

  • no more photosynthesis can occur regardless of how much more light is added

• more light = more absorption = more photosynthesis

CO2 Concentration:

• same as substrate concentration v. rate of reaction from enzyme unit —> increase, then plateau

• REMEMBER: CO2 is a reactant (acts as a substrate for Rubisco)

• initially, an increase in CO2 concentration causes an increase in the rate of photosynthesis

• eventually, a maximum rate is reached & the rate of photosynthesis plateaus

Temperature:

• parabola-shaped, with a peak

• REMEMBER: there are a LOT of enzymes involved in photosynthesis

  • enzymes susceptible to denaturation

• initially, an increase in temperature causes an increase in the rate of photosynthesis bc there’s an increasing number of collisions (molecular movement)

• above the optimum temp, the rate drops bc of enzyme denaturation

CO2 Enrichment Experiments:

• Scientists are conducting CO2 enrichment experiments

  • CO2 concentrations are rising in our environment

  • scientists study how plants will react to increased levels of CO2

    • CO2 enrichment experiments: increased amounts of CO2 in the atmosphere

• How are Greenhouses with manipulated CO2 concentrations used?

  • increased concentration in the greenhouse

  • measure biomass compared to a control

  • Pro: tighter control

  • Con: “artificial” environment

• Free-air Carbon dioxide Enrichment Experiments (FACE)

  • in open air

  • pipes surround the area & release CO2 into the atmosphere

  • sensors monitor CO2 levels

  • Pros: carried out in a natural ecosystem

  • Cons: expensive & harder to control