Development of Leaf Lobing and Vein Pattern Architecture in the GenusIpomoea(Morning Glory)

Abstract

Premise of research. Formation of leaf shape and establishment of vascular pattern are intrinsically tied during development. While vein formation resists major changes in patterning, leaf shape is more liable to change. We investigated the pattern of major vascular strands among species with varying leaf shapes within the genus Ipomoea (Convolvulaceae). Our study was conducted to identify structural similarities in vascular architecture despite differences in leaf morphology.Methodology. We used SEM to observe the initiation and formation of leaf lobes, while vascular strand development was examined in cleared leaves. A generalized Procrustes analysis was used to analyze branching patterns of the major secondary veins.Pivotal results. Analysis of vascular strands in the five Ipomoea species revealed that the two most proximal major secondary veins emerging from the petiole-blade junction are highly conserved, and the shapes defined by the trajectories of those veins through the leaf blade show significant overlap among the divergent leaf forms.Conclusions. The longitudinal arrangement of vascular strands is highly reproducible, while leaf morphology is amenable to changes within species. Our data show that a common vascular architecture exists and that significant consistencies can be seen in the basic shape described by this architecture across species.