XVI International Botanical Congess

Little is known about the relative influence of leaf cell layers in the regulation of leaf size and cell number. Graft chimeras were synthesized between 2 Nicotiana genotypes, one (Abig@) has leaves with mean areas 4X the other (Asmall@). Leaves from mericlinal chimeras, where the epidermis of either the Alarge@ or the Asmall@ genotype was present on only one side of the leaf midvein, were isolated and analyzed. When a Asmall@ epidermis existed over a Abig@ mesophyll, that side of the leaf was disproportionately smaller in area and possessed less epidermal and mesophyll cells. When a Abig@ epidermis existed over a Asmall@ mesophyll, that side of the leaf was disproportionately larger in area and possessed more epidermal and mesophyll cells. Therefore, mesophyll is subject to the influence of the epidermis. Leaf shape did not appear to be affected by the genotype of the epidermis.