The document discusses factors that affect the rate of photosynthesis in plants, including light intensity, carbon dioxide levels, and temperature. It states that initially increasing levels of these factors increases the photosynthesis rate, but the rate levels off at their maximum. Temperature peaks and then the rate decreases if it is too high. The role of the enzyme rubisco is also discussed, which incorporates carbon dioxide but can also incorporate oxygen if levels are high.

1. Factors Affecting Rate of
Photosynthesis

2. Factors that affect photosynthesis
 The rate at which plants carry out photosynthesis is
affected by the plant’s environment.
 Three very important factors that can affect the rate of
photosynthesis:
 Light intensity
 Level of CO2
 Temperature

3. Light Intensity
 As the light intensity increases, the rate of photosynthesis
increases, and then levels off.
 Leveling off represents maximum rate of photosynthesis.

4. Temperature
 Initially, as temperature increases, the rate of
photosynthesis increases.
 The rate peaks and then starts to decreases because:
 Enzymes that catalyze the reactions become
ineffective.
 Stomata start to close, limiting water loss and entry
of carbon dioxide.

5. Oxygen Concentration
What would a graph for increasing levels of CO2 look like?

6. Level of CO2
 As the level of CO2 increases, the rate of photosynthesis
increases, and then levels off.
 Leveling off represents maximum rate of photosynthesis.

7. Why Does Oxygen Effect
Photosynthetic Rate?
 What is the role of rubisco?
 Rubisco incorporates carbon dioxide into
the RuBP during the Calvin cycle.
 Rubisco, however, has an active site that
accommodates both oxygen and carbon
dioxide.
 What happens when rubisco incorporates
oxygen into the RuBP molecule?

8. Limiting Factors
 Law of Limiting Factors: rate of a physiological
process will be limited by the factor which is in
shortest supply. Any change in the level of a
limiting factor will affect the rate of reaction.