Unravelling the impacts of phosphorus deficiency on the photosynthetic machinery to determine the phosphorus status of plants

PhD defence by Andreas Carstensen


Phosphorus (P) is an essential plant nutrient with a structural role in nucleic acids, ATP, NADPH, and phospholipids. Phosphorus deficiency is a major limiting factor in global plant production, and the main source of P fertilizer (rock phosphate) is a finite and non-renewable resource, predicted to become limited in the future. Estimating plant available P in the soil is usually associated with many uncertainties, and the correlation between extracted P and true plant P uptake is often poor when using the classic soil P extraction analyses. Consequently, there is an urgent need for better real-time estimations of P status in plants.
This PhD study investigated chlorophyll a fluorescence as a new analytical approach to reveal the P status of plants directly in the field. The chlorophyll a fluorescence fingerprint is a reliable probe of photochemistry, and the sensitive signal is a powerful tool for detecting multiple plant stresses.
The work demonstrated that P deficiency caused specific changes in the chlorophyll a fluorescence transient, which was correlated with the current plant P status. Furthermore, a prediction model was developed to estimate the P status of plants using chlorophyll a fluorescence measurements. The mechanisms behind the discovery were further described by presenting a comprehensive biological model for how P deficiency affects the photosynthetic machinery. Finally, a new handheld device for detecting P deficiency was developed, which was shown to provide a unique opportunity for a timely correction of P deficiency under field conditions.
The PhD thesis concludes that chlorophyll a fluorescence is a promising method for revealing P status of plants, thereby providing a unique opportunity for timely detection of P deficiency in agriculture, with the potential to increase P use efficiency in global plant production.

Assessment Committee:​​​

Martin Broadley, Professor, University of Nottingham, United Kingdom
Gitte Rubæk, Associate professor, Aarhus University, Denmark
Poul Erik Jensen, (Chairman) Profess​or, University of Copenhagen, Denmark


Søren Husted, Professor, University of Copenhagen, Denmark

The defence is followed by a reception on the 3rd floor in meeting room R322/R323​