Senescence and nitrogen remobilization at plant level as affected by carbon and nitrogen source variation

Reduced nitrogen supply and elevated atmospheric carbon dioxide concentrations both reduce the amount of nitrogen available for grain/seed filling from pools in vegetative tissues. However, green leaves with lower N content due to CO2 enrichment are physiologically fully functional in terms of carbon gain since their reduced N content represents a physiological adaptation and optimisation of N allocation within the photosynthetic apparatus to increased C supply. The working hypotheses of this project are that modified lines of crops with improved N remobilization during leaf senescence will show improved nitrogen use efficiency and nitrogen harvest index, but will not overcome the imbalance between C and N acquisition caused by elevated CO2. Based on prior observations with oilseed rape, CO2 enrichment is also expected to potentially initiate vegetative growth when plants are already in the generative stage. In order to test these hypotheses, growth experiments will be performed with oilseed rape and barley under varying N and CO2 supply. N and C acquisition, remobilization and redistribution during the entire life cycle will be assessed involving 15N as tracer. Experiments will involve modified lines and wild types of recent cultivars, but also old cultivars differing in grain/seed nitrogen content und nitrogen harvest index.

Insitute for Landscape and Plant EcologyHohenheim
University of Hohenheim, Germany

Prof. Dr. Andreas Fangmeier
Matthias Müller

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