Measuring photosynthesis parameters in the field: how to create a fully working leaf dynamic photosynthesis model?

In nature, photosynthesis of field crops depends on environmental conditions like temperature, humidity and sunlight intensity. When these conditions are stable (do not change over time), the processes that control photosynthesis are stable as well. Examples of these processes are stomatal movement, Rubisco activity and electron transport. Under stable environmental conditions, these processes are in a so-called steady-state. In that case, a value for the steady-state rate at which these processes operate can be obtained using gas exchange measurements. However, environmental conditions can change rapidly throughout the day. Especially sunlight intensity on leaves tends to change a lot, due to a changing position of the sun, passing clouds or shadowing by plants and leaves higher up in the canopy. Stomata, Rubisco activity and electron transport respond to such rapid changes, but do so with a delay and not instantaneously: there is a response time. Similar to steady-state values, also these response times can be obtained by doing gas exchange measurements. When both the steady-state values and response times (i.e. photosynthesis parameters) of processes controlling photosynthesis are known, we can predict the behaviour of leaf photosynthesis under any type of environmental conditions. This is useful for, for example, estimating the losses in crop production due to slow responses of photosynthesis to fluctuating sunlight.

Used skills

In this project you will do real field work, as you will derive these photosynthesis parameters by performing leaf gas exchange measurements on a field-grown summer wheat crop close to Wageningen campus. The gas exchange measurements are done using a Li-Cor 6400XT or 6800 portable photosynthesis machine. Furthermore, your task will be to analysis the measurements and derive the model parameters required for operating a leaf dynamic photosynthesis model. The start of your project will be tied to the growing season of the summer wheat (April – June).

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