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Quantifying the impact of photorespiration on the photosynthetic carbon uptake of plants

Primary Supervisor: Dr Florian Busch, School of Biosciences

Secondary supervisor: Rob MacKenzie

PhD project title: Quantifying the impact of photorespiration on the photosynthetic carbon uptake of plants

University of Registration: University of Birmingham

Project outline:

    The main interest of the Busch laboratory revolves around the physiological functioning of plants. Projects focus on the fundamental nature of processes related to photosynthesis. Theoretical approaches involving mathematical modelling are combined with experimental approaches that are used to test the developed models. In combination, this allows for a prediction of plant responses to their environment on scales from the molecular level to the global carbon cycle.

    Photosynthesis is the most important biochemical process on earth, providing the energy for almost all life on the planet and generates food for a human population of 7+ billion people. It is the aggregate result of different molecular, biochemical and biophysical processes that, as a sum, determine how effective a plant is in converting sun light and nutrients into plant biomass. The key enzyme responsible CO2 fixation is called Rubisco. In addition to CO2, it can also react with oxygen, which results in the subsequent release of previously fixed CO2. This process, photorespiration, is therefore often considered wasteful and considerable research efforts are directed at minimising photorespiration in crop plants. However, photorespiration also has many beneficial aspects and can even increase the overall CO2 uptake of plants, despite decreasing the efficiency of the carboxylation reaction of Rubisco.

    The rate of photorespiration depends on many environmental factors, such as temperature and atmospheric CO2concentration. While higher temperatures promote photorespiratory CO2 release, higher CO2 concentrations decrease it. Quantifying the CO2 uptake of plants therefore requires a detailed understanding of how photorespiration responds to changes in the environment. This is particularly important for predicting the effects of climate change on plant productivity, as both temperatures and CO2 concentrations are expected to increase in the future. Understanding the effects of photorespiration under different environmental conditions is thus necessary for choosing successful strategies for crop improvement or deciding whether photorespiration should be attempted to be reduced in the first place. It is also paramount to forecasting future carbon uptake of forests. 

    This PhD project aims at quantifying the positive/negative effects of photorespiration and its impact on the overall carbon balance of plants. Experiments under highly controlled conditions in the laboratory will be supplemented with observations on trees growing at the Birmingham Institute of Forest Research free air carbon dioxide enrichment (BIFor FACE) facility ( The project will include using and developing mathematical models of biochemical processes and assessing physiological properties of crop plants and trees via photosynthetic gas exchange and chlorophyll fluorescence techniques.

    Further reading:

    1. Busch FA. 2020. Photorespiration in the context of Rubisco biochemistry, CO2 diffusion and metabolism. The Plant Journal 101(4): 919-939.
    2. Busch FA, Sage RF, Farquhar GD. 2018. Plants increase CO2 uptake by assimilating nitrogen via the photorespiratory pathway. Nature Plants 4(1): 46-54.

    BBSRC Strategic Research Priority: Sustainable Agriculture and Food: Plant and Crop Science & Understanding the Rules of Life: Plant Science

    Techniques that will be undertaken during the project:

    • Mathematical modelling
    • Photosynthetic gas exchange
    • Chlorophyll a fluorescence

    Contact: Dr Florian Busch, University of Birmingham