ConceptConceptDocsDocuments

IB Biology SL 1.3.7 Limiting Factors in Photosynthesis

Practise identifying limiting factors in photosynthesis, interpreting light, carbon dioxide and temperature data, and evaluating controlled experiments that measure reaction rate.

Syllabus
First assessment 2025
Course
Biology SL
Level
SL

Exam points

  • Interpret limiting-factor graphs and identify whether light, carbon dioxide or temperature controls rate.
  • Calculate or compare photosynthesis rates from oxygen, carbon dioxide and biomass measurements.
  • Evaluate experiments using controls, controlled variables and evidence from plotted data.

C1.3.7—Limiting factors investigation question 1

[Maximum number: 1]

C1. Global atmospheric carbon dioxide levels are rising. A study was carried out to test if the temperature dependence of photosynthesis was altered by elevated atmospheric CO2\mathrm{CO}_{2}. Maize plants were grown in natural sunlight in controlled environmental chambers at different temperatures using current atmospheric and doubled CO2\mathrm{CO}_{2} levels.

The graph below shows daily patterns of CO2\mathrm{CO}_{2} exchange at three different temperatures. Open shapes ( o,Δ,v\mathrm{o}, \Delta, \mathrm{v} ) represent current atmospheric CO2\mathrm{CO}_{2} levels and closed shapes ( ∙,Δ,m\bullet, \mathbf{\Delta}, \mathbf{m} ) represent elevated CO2\mathrm{CO}_{2} levels.

Figure for Question C1.3.7—Limiting factors investigation question 1 — IB Biology SL

State the temperature that resulted in the highest rate of photosynthesis under current atmospheric conditions.

All question bank results loaded