Development of leaves and flowers in the wild type and pleiotropic maplewillow mutant of Japanese morning glory (Ipomoea nil)

The development of leaves and flowers in the wild type and pleiotropic maple-willow (m) mutant of Japanese morning glory (Ipomoea nil) was studied to reveal the developmental and regional homology and effects of the m gene on the lateral organs. The considerably narrow leaves, sepals, and petals of the m mutant result from the inactive marginal meristem, and the small thecae of anthers and the defective septa of ovaries in the m mutant arc also due to insufficient marginal growth. This suggests that the defective regions of all lateral organs in the m mutant are developmentally homologous under regulation by the m gene. In the wild type, the fusion of the marginal growth of neighboring primordia is followed by upward growth in the interprimordial regions of floral organs, but in the m mutant the defects of this upward growth in the interprimordial regions in the corolla and gynoecium result in apopetalous and apocarpous forms, respectively, except for their normally fused lower portions. It seems that both sympetalous corolla and syncarpous gynoecium of I. nil are formed by two different developmental processes, namely, interprimordial growth and intercalary or zonal growth. JSHS © 2009.