The question of which cellular mechanisms determine the variation in leaf size has been previously addressed in plants with simple leaves. Dissecting compound tomato (Solanum lycopersicum) leaves in leaflet areas and in cellular traits, Koch et al. show that leaf area variation along the shoot is related to leaflet area and epidermal cell number.
In contrast, epidermal cell size and endoreduplication of the nuclei do not vary substantially with heteroblasty progression and were uncoupled. Both in well-watered and drought treatments, all leaflets on a single leaf have the same cellular phenotypes.