Limiting Factors in Photosynthesis (Higher Tier) Revision Notes | GCSE OCR Foundation Biology

What this lesson covers

Explore how multiple factors interact to limit photosynthesis, analyze complex graphs with multiple variables, understand the inverse square law with li...

• Explain how temperature, light intensity, and carbon dioxide concentration act as limiting factors in photosynthesis
• Interpret graphs showing photosynthesis rates with multiple limiting factors and identify which factor is limiting
• Apply the inverse square law to calculate light intensity at different distances from a light source
• Evaluate the economic considerations of enhancing greenhouse conditions to maximise photosynthesis while maintaining profit

Key ideas to keep in view

Use this lesson to stay inside B1.4 Photosynthesis while connecting the detail back to the wider B1: Cell level systems topic.

• B1: Cell level systems
• B1.4 Photosynthesis
• GCSE OCR Foundation Biology

Lesson notes preview

Read the core explanations from Limiting Factors in Photosynthesis (Higher Tier) before testing yourself from memory.

• 1. Why Plants Can't Always Work at Full Speed
• Picture a factory assembly line making cars. Even with the best workers, if you run out of steel, production stops. Plants face the same problem with photosynthesis.
• Photosynthesis needs three key ingredients: light, carbon dioxide, and the right temperature. When any one of these runs short, it becomes the bottleneck that slows everything down. This bottleneck is called the limiting factor.
• The environmental condition that restricts the rate of photosynthesis when it is in shortest supply. Even if other conditions are perfect, the rate cannot increase beyond what this factor allows.
• Trap: Many students think all three factors must be low to limit photosynthesis. Actually, just ONE factor being in short supply will limit the entire process, no matter how abundant the others are.
• Each limiting factor affects photosynthesis in a specific way. Let's examine how temperature, light intensity, and carbon dioxide concentration control the rate.
• Temperature: Controls enzyme activity in photosynthesis. Too low and enzymes work slowly. Too high and enzymes denature. The optimum is usually around 25-30°C for most plants.
• Light Intensity: Provides the energy for photosynthesis. More light means more energy available, but only up to a point where other factors become limiting.
• Carbon Dioxide Concentration: Provides the carbon atoms needed to make glucose. Normal air contains only 0.04% CO₂, so this often limits photosynthesis before light does.
• 3. Reading Limiting Factor Graphs Like a Detective

Continue through the topic

Move to the related lessons or back to the topic page when you need the wider sequence before exam-style practice.