Elucidating the positive and negative effects of leaf nitrogen
source on photosynthetic capacity in legumes and cereals –
in collaboration with Efrat Sheffer (funded by Schonberger
Research Center for Plant Science in Agriculture.

​Grain legumes are a critical and inexpensive source of plant-based protein, vitamins, and minerals and therefore have an essential role in food security. Legumes can derive their nitrogen (N) requirements from symbiotic nitrogen fixation via bacteria hosted in root nodules. The nitrogen-fixing capacity of legumes offers an alternative for reducing the use of synthetic nitrogen fertilizers, thus lowering the cost to farmers and the impacts of chemical fertilizer use on ecosystems. In this proposal, we argue that despite the strong relationship between carbon assimilation and nitrogen (as N is essential for the biosynthesis of chlorophyll), the correlation between rate of photosynthesis and the concentration of nitrogen in the leaf is relatively low in legumes compared to cereals. Real-time isotope flux measurements accompanied by measurements of gas exchange and chlorophyll fluorescence have opened the door for a better understanding of the influence of nitrogen on carbon assimilation. We aim to investigate the response of photosynthesis to varying sources of nitrogen nutrition, identify the traits controlling the relationship between leaf nitrogen and photosynthesis in legumes and cereals, and quantify the contribution of symbiotic N2 fixation to the process of photosynthesis. This research could unravel mechanisms that offer novel strategies for improvement of photosynthetic nitrogen use efficiency (PNUE) and yield in many important crop species.