Résumé
Leaf area expansion is affected by many environmental conditions including incident light, soil water content, and day-length. At the cellular level, these changes are associated with differences in cell number and/or cell size, but also with differences in the extent of endoreduplication. The functional relationships between cellular processes and leaf area expansion have been evaluated by mutational analysis and the study of transgenic lines. A few studies have shown that the regulation of leaf size could be disrupted by alterations in genes involved in cell division, cell expansion or endoreduplication, but many attempts to increase leaf size by modifying cell division or expansion have failed. A multi-scale high-throughput phenotyping and modeling approach was used in our group to determine how these cellular processes interact with the regulation of leaf area expansion both in collections of accessions, populations of recombinant inbred lines and selected mutants affected either in endoreduplication, in cell cycle regulation or in cell expansion. Both the quantitative genetics and statistical modelling approaches lead to the conclusion that these three cellular processes are controlled, at least to some extent, by whole leaf and whole plant developmental processes. As a consequence, their impact on leaf growth itself is expected to be limited which is consistent with many experimental results.