Clonal analysis of leaf development in maize

Clonal analysis was used to characterize the cell lineage and cell division pattern of the maize leaf. Periclinal chimeral leaves, and clones induced one plastochron prior to the initiation of the disk of insertion (Sharman, 1942), suggest that this leaf/internode primordium arises from two, or possibly three tiers of cells in the shoot meristem, is approximately 30 cells in circumference, and encompasses at least two layers of the shoot meristem. All of the cells in the L2 layer of disk of insertion have the potential to contribute to one or more of the following parts of the leaf and culm: internode, node, leaf sheath and leaf blade. Founder cells do not contribute equally to the growth of the leaf because they are recruited to the primordium at different times in development, and because the orientation of cell division is more polarized at the tip of the leaf than that at its base. During the early phase of leaf expansion (starting at about 15 mm), the rate of mitosis is significantly higher in one or two localized regions at the base of the leaf than in any other region. Cell division ceases basipetally, starting when the primordium is two to three cm long. The striking similarity between the cell division patterns of maize and tobacco leaves demonstrates that is misleading to ascribe the growth of the maize leaf to a basal intercalary meristem, unless the definition of this term is broadened to include any leaf that matures basipetally