Nitrogen shortage in a tomato crop; Scaling up from effects on electron-transport rate to plant productivity

Optimization of nitrogen supply in a tomato plant is stepwise assessed, fro m chloroplast characteristics to whole crop performance. Experiments are re ported in which important key processes are quantified in relation to the n itrogen content of leaves. Interactions of N effects with leaf aging and ca nopy light distribution are analyzed. A simulation model that integrates this knowledge is constructed. The resul ts of three nitrogen partitioning scenarios for Rubisco suggest that optimi zation of the distribution of Rubisco between leaf layers is less important for plant productivity than within-leaf optimization of the photosynthetic apparatus.