How do differences in cell number and cell size contribute to the control of leaf size under shading?
Theories of leaf size control have been debated for many years (e.g. Fleming, 2002; Tsukaya, 2003). According to the classical cell theory, a cell is the basic unit of a multicellular organism and is therefore the unit of organogenesis. Evidence for this theory is often based upon the positive relationship between cell number and final organ size (e.g. Granier et al., 2000; Cookson et al., 2005). According to the organismal theory, genetic information specifies the form of leaves independent of sizes and shapes of cells; thus leaf size control is at the scale of the whole organ. Evidence for this theory is often based on the observation that organ size and/or shape can be maintained to some degree when cell division is blocked or decreased in plant organs (e.g. Haber and Foard, 1963; Hemerly et al., 1995). To reconcile the two aforementioned theories and integrate them with additional observations the neo cell theory has been proposed in which there is a compensatory system of leaf siz
