Branching morphology, vascular bundle arrangement and ontogenetic development in leaf insertion zones and ramifications of three arborescent Araliaceae species

Abstract

Key message A conspicuous 'finger-like' branching morphology is described for three arborescent Araliaceae species with a focus on the three-dimensional vascular bundle arrangement in leaf insertion and stem-branch attachment regions during ontogenetic development. Abstract The central aim of this study is to gain a deeper understanding of the structure and development in leaf insertions and stem-branch attachments of the arborescent Araliaceae species: Schefflera arboricola, Fatsia japonica and Polyscias balfouriana. Therefore, the vascular bundle arrangement in the leaf insertion zone and ontogenetic development of the stem-branch attachment after decapitation were analyzed, with a special focus on their conspicuous 'finger-like' branching morphology that, to our knowledge, is unique to the Araliaceae. Decortication of adult ramifications allows for a morphological analysis of the woody strands in the stem-branch attachment regions. Via high-resolution microscopy of serial thin-sections and 3D reconstructions, as well as cryotome sections, anatomical analysis was carried out of the course and arrangement of vascular bundles through leaf insertions and later developing ramifications, including a comparative analysis of the different ontogenetic stages. All three species investigated present a 'finger-like' branching morphology with variations in the number and arrangement of the woody strands. Thin-sectioning reveals a conspicuous pattern of leaf trace emergence from the main stem, proceeding into the leaf and the early developing ramifications. Vascular bundle derivatives contribute to the vascular integration of leaves and axillary buds. The described 'finger-like' branching morphology in the investigated Araliaceae species represents a sophisticated mode of vascular integration in leaf insertion zones and developing ramifications. In combination with forthcoming biomechanical experiments, this analysis shall serve as a basis for biomimetic translations into textile technology (fiber-reinforced branched composite materials) and civil engineering (optimization of branched building structures).

4D pine scale: biomimetic 4D printed autonomous scale and flap structures capable of multi-phase movement

“…Depicting the anatomical complexity of pinecone seed scales (figure 1) required histological examinations. Natural pinecone seed scales were embedded and cut as semi-thin cross or longitudinal sections after a protocol published in [36]. We applied either toluidine-blue staining (infiltration for 2 min in toluidine C.I.…”

Plants and architecture: the role of biology and biomimetics in materials development for buildings

“…Here the prominent vascular bundle arrangement at leaf insertion zones provided inspiration to consider fibre composite sheathing for concrete structures, to retain or enhance performance at branching points. Fundamental principles were abstracted from the ramifications at the branching points within the plant for application to fibre reinforced plastic tubes (Bunk et al 2017).…”

Branching morphology and biomechanics of ivy (Hedera helix) stem‐branch attachments

“…This continuous process is the reason for the existence of many transitional forms between the three discerned fusion levels. In other Araliaceae species with a "finger-like" branching morphology, such as the tropical Araliaceae Schefflera arboricola, Fatsia japonica, and Polyscias balfouriana (Tomlinson et al, 2005;Bunk et al, 2017a), fusion of the woody strands and the formation of DoF1 also occurs, but a complete fusion up to DoF2 has until now not been observed. Probably, the rate of woody strand coalescence depends on both species and growth site.…”

“…A conspicuous branching morphology has been identified in the tropical Araliaceae genera Schefflera (Fig. 1), Fatsia, and Polyscias (Tomlinson et al, 2005;Bunk et al, 2017a). The stem and branch are connected via individual woody strands, which merge in the side branch (Tomlinson et al, 2005;Bunk et al, 2017a).…”

“…1), Fatsia, and Polyscias (Tomlinson et al, 2005;Bunk et al, 2017a). The stem and branch are connected via individual woody strands, which merge in the side branch (Tomlinson et al, 2005;Bunk et al, 2017a). Due to its appearance, this branching morphology has been described as "finger-like" (Tomlinson et al, 2005), a term that has been further established in ongoing research (Born et al, 2016;Bunk et al, 2017a, b).…”