Abstract
The structure of leaves and flowers of wild-type and pleiotropic maple-willow (mw) mutant strain of Japanese morning glory (Ipomoea nil) was studied. The results provide a standard description for the morphology of I. nil and the morphological effects of this mw mutant on all lateral organs. We found that the mw mutation decreases the lamina width of all lateral organs by reducing cells in the transverse direction. We also established that the mw mutation transforms the tri-lobed leaf into a slender willow-like leaf. It also results in the absence of the short tube in the calyx, changes the funnel-shaped sympetalous corolla to almost apopetalous, and modifies the normally syncarpous gynoecium to nearly apocarpous. The mw mutation may cause a pleiotropic morphological phenotype of leaf and floral organs by reducing their lateral growth and fusing regions in the calyx, corolla, and gynoecium; however, the lower corolla tube and the septa and placentas of the lower portion of the ovary are as in the wild-type. Therefore, we suggest that in the mature leaf and floral organ structures, the homologous portions that may be formed by the same developmental processes are morphologically distinct. The MAPLE gene may be involved in lamina width growth and organ fusion in all lateral organs.
