Abstract
Leaf size depend on the number and size of cells. However, leaves are not a simple sum of cell size and number, but are under the control of an unknown, organ-wide integration system. The existence of an integration system is strongly suggested by two mysterious phenomena: compensation and high-ploidy syndrome. Compensation is characterized by enhanced cell enlargement that is triggered by a significant decrease in cell proliferation; high-ploidy syndrome is a phenomenon by which plants with ploidy higher than 8C result in increased cell volume, but smaller leaves. The mechanisms behind these phenomena are unknown. These types of system have not expected from studies of unicellular organisms such as yeast at all. The resolution of these phenomena should provide several important clues to understanding the mechanisms of multicellular organogenesis. We will introduce our present models on these mechanisms deduced from analyses of Arabidopsis mutants and tetraploids.
