Branching morphology of decapitated arborescent monocotyledons with secondary growth.

Abstract

• Dragon trees (Dracaenaceae) are arborescent monocotyledons with anomalous secondary growth and are able to branch, exhibiting a treelike habit. Studies of the morphology and anatomy of ramifications allow for a better understanding of the complex course and arrangement of the vascular bundles in the stem-branch attachment region for Dracaena and other arborescent monocots with anomalous secondary growth.• Morphological and anatomical analyses of ramifications induced in decapitated specimens of D. marginata and D. reflexa included serial sectioning, maceration, staining, and bleaching techniques as well as high and low resolution optical microscopy and three-dimensional (3D)-visualization techniques.• The use of innovative 3D reconstruction and high-resolution imaging revealed the extent of connections between branch and stem on various hierarchical levels in Dracaena A stem-clasping attachment of the side shoot was observed, which in more detail shows a strong regional dependence of course and connectivity of individual vascular bundles to the main stem. Consequently, the attachment of branch tissue is strongly limited to the outer periphery of the main stem.• Our results indicate that the observed course of vascular bundles with fiber caps cannot only be a result of physiological need for water and nutrient supply but are interpreted in terms of mechanical constraints acting on the branching region. In addition, the used 3D cine technique and coupled 3D reconstruction provide a valuable tool for botanists working in the field of anatomy.