Photosynthetic CO2 re-fixation using Oxygen response of photorespiration

Hirschfeldia incana (Grey mustard) is used in the Extremophile programme of Wageningen University as a model species with a very high rate of photosynthesis under high light. Initial gas exchange measurements show higher rate of Hirschfeldia incana under high light conditions in comparison to Brassica nigra, Brassica rapa and Arabidopsis thaliana.


Several factors may contribute to the high photosynthesis performance. High biochemical capacity influenced by high leaf nitrogen content, efficient electron transport and efficient gas transport are some of the potential factors. In this research, it is hypothesized that efficient re-fixation of (photo)respired CO2 contributes significantly to the high photosynthesis rate of H. Incana. Effective re-fixation of (photo)respired CO2 is influenced by leaf anatomy as chloroplast-mitochondria arrangement and chloroplast coverage of mesophyll surface area exposed to intercellular airspaces influence the fate of the released CO2. The extent  of re-fixation of (photo)respired CO2 and anatomical factors are examined using experiment and mathematical modelling.


Hirschfeldia incanaBrassica rapa and Arabidopsis thaliana are grown in climate chamber. The light and CO2 responses of photosynthesis are measured at several oxygen levels using combined gas exchange and chlorophyll fluorescence measurements. The extent of re-fixation of (photo)respired CO2 is then estimated using mathematical modelling using the method reported here. The anatomy of the leaf is examined using light and electron microscopy.


You will be able to generate insights on how to improve leaf photosynthesis rate through efficient gas diffusion and leaf anatomy. You will be able to identify leaf anatomical traits contributing to efficient re-fixation and hence photosynthesis. These insights has strong implication on improving crop yield through efficient photosynthesis.

This thesis topic is suitable for MSc.