Structure, attachment properties, and ecological importance of the attachment system of English ivy (Hedera helix)

Abstract

Root climbers such as English ivy (Hedera helix) rely on specialized adventitious roots for attachment, enabling the plants to climb on a wide range of natural and artificial substrates. Despite their importance for the climbing habit, the biomechanical properties of these specialized adventitious roots compared with standard roots and their performance in the attachment to different host species or inert substrates have not been studied. Here organs and tissues involved in the attachment are characterized and their significance in regard to a broader functional and ecological aspect is discussed. Depending on the substrate, the root clusters show different types of failure modes at various frequencies, demonstrating the close interaction between the climber and its substrates. With a Young’s Modulus of 109.2 MPa, the attachment roots are relatively stiff for non-woody roots. The central cylinders of the attachment roots show a high tensile strength of 38 MPa and a very high extensibility of 34%. In host trees naturally co-distributed with English ivy, a ‘balanced’ occurrence of failure of the attachment system of the climber and the bark of the host is found, suggesting a co-evolution of climber and host. Maximum loads of root clusters normalized by the number of roots match those of individually tested attachment roots. In comparison with most subterranean roots the properties and structure of the attachment roots of English ivy show distinct differences. There exist similarities to the properties found for roots of Galium aparine, suggesting a trend in not fully self-supporting plants towards a higher extensibility.

Mechanical Innovations of a Climbing Cactus: Functional Insights for a New Generation of Growing Robots

“…The root adhesion system in Selenicereus follows initial hook attachment and firmly anchors segments of stem to a range of support substrates. Root attaching mechanisms are well described for English ivy and also entail a multi-step mechanism of passive and active processes at the micro to nano scale (Melzer et al, 2010(Melzer et al, , 2012. To our knowledge, as yet there is no published account of "growth-like" technologies that could mimic this kind of attachment in either apical additive engineering growth artifacts or pre-formed, telescoping/everting and continuum technologies.…”

Nanospherical arabinogalactan proteins are a key component of the high-strength adhesive secreted by English ivy

“…1A). Previous studies have emphasized mechanical strategies exploited by multiple climbing organs that evolve in plants (7)(8)(9)(10)(11). Nevertheless, the role of the glue-like viscous exudates that are observed on the majority of these organs and that cement the plants to the substrates has been less explored (10,12,13).…”

Using multiple traits to assess the potential of introduced and native vines to proliferate in a tropical region

“…In particular, one group of proliferating species was composed of vines with horticultural, ornamental, or medicinal uses, and with aerial roots or a scandent climbing mechanism. Root climbers can utilize their specialized adhesive roots to attach to a wide range of natural and artificial substrates (Melzer, Seidel, Strinbrecher, & Speck, ), which can facilitate their establishment in a wider range of habitats. Scandent vines, on the other hand, can live as shrubs when trellis is not available (Dey, ), which can function as an advantage when colonizing new environments.…”