Anatomy and Biomechanics of Peltate Begonia Leaves—Comparative Case Studies

Abstract

Plants are exposed to various external stresses influencing physiology, anatomy, and morphology. Shape, geometry, and size of shoots and leaves are particularly affected. Among the latter, peltate leaves are not very common and so far, only few studies focused on their properties. In this case study, four Begonia species with different leaf shapes and petiole attachment points were analyzed regarding their leaf morphology, anatomy, and biomechanical properties. One to two plants per species were examined. In all four species, the petiole showed differently sized vascular bundles arranged in a peripheral ring and subepidermal collenchyma. These anatomical characteristics, low leaf dry mass, and low amount of lignified tissue in the petiole point toward turgor pressure as crucial for leaf stability. The petiole-lamina transition zone shows a different organization in leaves with a more central (peltate) and lateral petiole insertion. While in non-peltate leaves simple fiber branching is present, peltate leaves show a more complex reticulate fiber arrangement. Tensile and bending tests revealed similar structural Young’s moduli in all species for intercostal areas and venation, but differences in the petiole. The analysis of the leaves highlights the properties of petiole and the petiole-lamina transition zone that are needed to resist external stresses.

1092. Begonia hongkongensis F.W.Xing: Begoniaceae

“…However, no experimental studies have explored the biomechanical aspects of leaf base development under the influence of water currents. Nevertheless, a study of peltate leaf bases, another uncommon trait in Begonia , revealed a complex arrangement of fibers in the petiole, providing increased resistance at the junction point between the leaf blade and its stalk (Rjosk et al, 2022).…”

Longevity of System Functions in Biology and Biomimetics: A Matter of Robustness and Resilience

“…However, the total of all gradual and/or sudden changes of influencing variables determines whether the transition is smooth or abrupt ( Figure 4 ). In plant leaves, on the one hand, we find superimposed gradual transitions resulting in a damage-resistant transition zone between petiole and leaf lamina [ 63 , 67 , 68 , 69 ]. Moreover, we find abrupt transitions leading to a spatio-temporal controlled shedding of individual plant organs (abscission), such as between branches and petioles resulting in leaf fall in autumn [ 70 , 71 ].…”