Abstract
Nitrogen is fundamental for plant growth. In cereals, growing grains represent a strong sink that triggers nitrogen remobilisation from vegetative organs and results in plant death. A better understanding of this mechanism would help in optimizing crop productivity while reducing fertilization. This work presents an experimental analysis and a process–based model of the spatiotemporal nitrogen distribution during grain filling in winter wheat culms. Nitrogen was distributed homogeneously within individual laminae and sheaths, but a strong gradient existed between organs at successive positions along the culm. During grain filling, the changes in nitrogen content of individual laminae and sheaths showed identical patterns, differing only by a scale factor. Modelling N content of each lamina as the result of the turnover of photosynthetic nitrogen and supposing that all organs share a single pool of mobile nitrogen allowed predicting the observed patterns with high accuracy. This offers new insight for modelling plant nitrogen economy.