Film 1 shows how a young branch of a liana (Condylocarpon guianense, Apocynaceae) roves across supports near the forest floor and then climbs up a vertical support. Many climbers show this kind of “decision-making” of when and, when not, to attach and climb. It is a key developmental contingency that we want to understand and reproduce in the GrowBot project.
In film 2, we see that young stems of different species can have very different growth strategies: one species (Condylocarpon guianense) roves across the forest floor in search of supports while the other (Bauhinia guianensis, Fabaceae) produces small upright stems that are waiting for the right conditions (possibly light) to develop further vertical growth.
Film 3 shows what happens when a root-climbing plant encounters a change of substrate. Such changes represent an obstacle course and risk for climbing plants – as they do for robotic artefacts that need to traverse different substrates. In the natural world some plants are better at climbing on diverse substrates than others.
In Film 4 we see how old lianas can survive severe mechanical trauma when the host supporting tree falls. The tropical rainforest is a highly perturbed mechanical environment and lianas can show great survivability and autonomy following tree falls and branch falls. Their stem organisation changes drastically from the young climbing or roving axes we saw earlier to older resistant stems that can be highly flexible showing many mechanisms to protect against lethal fracture.
So old liana stems (Film 5) can therefore survive a lot of bending, twisting and kinking of the stem. We are measuring how these stems can survive such high levels of mechanical stress and how such features might be built into manufactured products.
There is a great diversity of “constructional types” of climbing plant in the tropical rainforest (Film 6). Light structured, cane-climbers of the Marantaceae (Ischnosiphon species) can lean and climb onto surrounding vegetation using light stems with very little biomass but with articulated, flexible nodes or “joints”. This is a completely different “model” of climbing stem compared with the woody lianas we see in the surrounding patch of forest.