Photosynthesis limiting factors: definition and examples.

📚 Quick Study Guide

• ☀️ Photosynthesis is the process where plants convert light energy into chemical energy.
• 💧 The basic equation: $6CO_2 + 6H_2O + light \rightarrow C_6H_{12}O_6 + 6O_2$
• 🌡️ Limiting factors are environmental conditions that restrict the rate of photosynthesis when in short supply.
• 🌱 Key limiting factors include:
• 💡 Light intensity: Affects the rate of light-dependent reactions.
• 🌡️ Temperature: Influences enzyme activity in the Calvin cycle.
• 💨 Carbon dioxide concentration: A substrate for the Calvin cycle.
• 💧 Water availability: Affects stomatal closure, limiting $CO_2$ uptake.
• 🧪 Liebig's Law of the Minimum: The rate of photosynthesis is limited by the factor that is most scarce.

🧪 Practice Quiz

1. Which of the following is NOT a limiting factor of photosynthesis?

   1. Light intensity
   2. Carbon dioxide concentration
   3. Oxygen concentration
   4. Temperature

2. What happens to the rate of photosynthesis as light intensity increases, assuming other factors are optimal?

   1. It decreases
   2. It increases up to a point, then plateaus
   3. It remains constant
   4. It fluctuates randomly

3. Why does water availability affect photosynthesis?

   1. It directly participates in the light-dependent reactions
   2. It helps maintain the structure of chloroplasts
   3. It affects stomatal closure, limiting $CO_2$ uptake
   4. It increases the rate of transpiration

4. At very high temperatures, the rate of photosynthesis decreases. Why?

   1. Because it favors photorespiration
   2. Because enzymes involved are denatured
   3. Because the stomata open wider
   4. Because the chlorophyll absorbs less light

5. What is the role of carbon dioxide in photosynthesis?

   1. It is an electron acceptor in the light-dependent reactions
   2. It is a substrate for the Calvin cycle
   3. It helps maintain the pH of the stroma
   4. It absorbs light energy

6. According to Liebig's Law of the Minimum, what determines the rate of photosynthesis?

   1. The sum of all available resources
   2. The average availability of all resources
   3. The most abundant resource
   4. The most scarce resource

7. How does low light intensity limit photosynthesis?

   1. It reduces the rate of carbon fixation
   2. It decreases the efficiency of the Calvin cycle
   3. It limits the production of ATP and NADPH
   4. It causes stomatal closure