Best practices for photosynthesis response curves

Photosynthesis drives plant growth, and is the basis for almost all life on Earth. To characterize the environmental dependencies of photosynthesis, scientists often obtain photosynthesis response curves, e.g. the response of photosynthetic CO2 uptake at a range of light intensities or CO2 concentrations. Parameters derived from such response curves are used in photosynthesis models, which help to predict e.g. forest growth under climate change, crop growth in various environments (field, greenhouse, vertical farms), or the Earth’s climate. However, best practices for obtaining and analysing (curve fitting) photosynthesis response curves are understudied. In stressed leaf material (e.g. salt stress), such quantifications can become even more difficult, as the rate of CO2 diffusion inside the leaf can become limiting for the accuracy that is required to calculate net CO2 uptake, or to reach a stable CO2 uptake rate. Also, the time of day can affect photosynthesis rates, and may thus have consequences for the shape of response curves. Additionally, efforts to breed for improved photosynthesis require its quantification in hundreds of genotypes at a time, driving the need for “rapid response curves”, which are sometimes claimed to deliver data of the same accuracy as ‘classical’ response curves that take longer to measure, but this is disputed. The way in which photosynthesis response curve data are obtained and analysed is not well tested or standardized, but can have strong effects on the estimation of parameters that feed into photosynthesis models, and therefore can have strong implications for predicted plant growth. In this project, you have the chance to answer a number of simple but highly relevant questions: what are the best practices for measuring and analysing photosynthesis response curves? Do different times of day affect response curves? Which trade-offs exist between speed and accuracy, and how strongly do they affect the outcome?

Used skills

• Gas exchange
• Chlorophyll fluorescence measurements
• Data analysis

Interested in doing a BSc or MSc thesis at HPP? Please contact the HPP student coordinator Katharina Hanika.