Department of Biology, Institute of Botany, Faculty of Science, Technische Universität Dresden, Germany.
Institute for Building Materials, ETH Zürich, Switzerland.
Ann Bot. 2020 Nov 24;126(7):1215-1223. doi: 10.1093/aob/mcaa149.
Fruit pedicels have to deal with increasing loads after pollination due to continuous growth of the fruits. Thus, they represent interesting tissues from a mechanical as well as a developmental point of view. However, only a few studies exist on fruit pedicels. In this study, we unravel the anatomy and structural-mechanical relationships of the pedicel of Adansonia digitata, reaching up to 90 cm in length.
Morphological and anatomical analyses included examination of stained cross-sections from various positions along the stalk as well as X-ray microtomography and scanning electron microscopy. For mechanical testing, fibre bundles derived from the mature pedicels were examined via tension tests. For establishing the structural-mechanical relationships, the density of the fibre bundles as well as their cellulose microfibril distribution and chemical composition were analysed.
While in the peduncle the vascular tissue and the fibres are arranged in a concentric ring-like way, this organization shifts to the polystelic structure of separate fibre bundles in the pedicel. The polystelic pedicel possesses five vascular strands that consist of strong bast fibre bundles. The fibre bundles have a Young's modulus of up to 5 GPa, a tensile strength of up to 400 MPa, a high density (>1 g cm-3) and a high microfibril angle of around 20°.
The structural arrangement as well as the combination of high density and high microfibril angle of the bast fibre bundles are probably optimized for bearing considerable strain in torsion and bending while at the same time allowing for carrying high-tension loads.
授粉后，由于果实的持续生长，果柄必须承受不断增加的负荷。因此，从力学和发育的角度来看，它们是很有趣的组织。然而，关于果柄的研究很少。在这项研究中，我们揭示了长达 90 厘米的猴面包树果柄的解剖结构和结构力学关系。
形态学和解剖学分析包括对茎干不同位置的染色横切片进行检查，以及 X 射线微断层扫描和扫描电子显微镜检查。为了进行力学测试，从成熟的果柄中提取纤维束进行拉伸测试。为了建立结构力学关系，分析了纤维束的密度及其纤维素微纤维的分布和化学组成。
在花梗中，维管组织和纤维呈同心环状排列，而这种组织在果柄中则转变为单独纤维束的多腔结构。多腔果柄有五条由强韧皮纤维束组成的维管束。纤维束的杨氏模量高达 5 GPa，拉伸强度高达 400 MPa，密度高（>1 g cm-3），微纤维角约为 20°。
韧皮纤维束的结构排列以及高密度和高微纤维角的组合，可能优化了其在扭转和弯曲时承受相当大应变的能力，同时又能承受高张力负载。
