Action of Gibberellic Acid on Cell Proliferation in the Subapical Shoot Meristem of Watermelon Seedlings

Rates of cell proliferation were about 2.5 fold greater in gibberellic acid‐treated seedlings of dwarf watermelon than in untreated dwarf seedlings as determined by direct counts of pith cells in elongating hypocotyls of watermelon. The higher rates of cell proliferation observed in normal and GA‐treated dwarf seedlings were due both to shorter cell cycle times and increased growth fractions of cells than in dwarf seedlings. The shorter duration of the cell cycle in GA‐treated seedlings was primarily due to a reduced S period.