Climbing growth forms are common among woody families of angiosperms, relatively common among monocots, but much rarer in other groups, including gymno-sperms and ferns. The mechanical properties of climbing stems as well as the type of attachment are undoubtedly coupled to a wide range of evolutionary constraints among different plant groups [19,20,26-29]. Most monocot climbers tested so far retain the relatively stiff properties of host location and initial stiff phase of growth. Such plants without secondary growth are unable to make the developmentally complex, though ecologically important, transition from high stiffness to high compliance of tissues. However, because of their small axial second moment of area, flexural stiffness also remains relatively low in old stems. Such climbing forms nevertheless occupy both small-bodied and large-bodied climbing niches and can show important diverse modes of climbing attachment. Only species of Calamus, arguably the most diverse and specialized group of climbing monocots, show relatively low values of Estr of the inner stem, which produces flexible canes after the loss of the leaf sheath. This particular mechanical architecture in Calamus could have been an important innovation in the group and might explain its ecological success in Southeast Asia.
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