1 Department of Functional Morphology and Biomechanics, Zoological Institute of the University of Kiel, Am Botanischen Garten 9, 24118 Kiel, Germany.
2 Plant Biomechanics Group & Botanic Garden, Faculty of Biology, University of Freiburg, Schänzlestr. 1, 79104 Freiburg, Germany,; Freiburg Institute for Interactive Materials & Bioinspired Technologies (FIT), 79104 Freiburg, Germany.