Productivity and grain or seed composition: a new approach to an old problem - invited paper

The research made in the last 20 years resulted an almost linear increase in average grain/seed yield for different crops, associated with a change in grain/seed composition: decrease in the protein concentration at the expense of compounds resulting from carbon metabolism (starch, oil). Due to the rapid development of biological sciences and the scope of the means available in modern research this progress was achieved. It merits a reflection about the key processes limiting the plant productivity and about an adaptation to an environment, often very conservative. The integration of crop yield limiting factors into plant and canopy activities was made in order to highlight research objectives and new approaches. After a general analysis of yield increase mechanisms, the processes determining crop yield and grain composition and the effects of species, cultivars, and environmental factors (temperature, drought, nitrogen) were analysed, For this a conceptual model was established based on the source-sink relationship, especially during the post-anthesis period, In order to successfully improve the yield potential and the composition of grain and seeds, new knowledge of the processes is required concerning the intrinsic properties of the plant organs (seeds, leaves, roots) and their interactions. Several priority themes were considered. (C) 2002 Elsevier Science B.V. All rights reserved.