Domino-like water transport on Tillandsia through flexible trichome wings.

Abstract

Tillandsia usneoides in epiphytic bromeliads takes up water through the absorptive trichomes on the shoot surface under extreme environmental conditions. Although previous studies revealed the way by which T. usneoides absorbs water and prevents water loss, T. usneoides water transport is still unclear. We characterized structures of trichome wings of T. usneoides. Wing length-to-thickness ratio with 136 and the trichome interval (d)-to-wing length (l) ratio (d/l) smaller than 1 caused the water film to flatten the wings sequentially, resulting the domino-like water transport. A hinge-like linkage between wing and outer ring cells and the wing size longer than the elastocapillary length (LEC ) brought about this unique reconfiguration, which is the flattening and recovery of wings. T. usneoides transported water rapidly on the surface as the water film propagated on the exterior trichomes with flexible wings and the transport distance at the macroscopic scale grew as tx with x = 0.68 ± 0.04, unlike the conventional scaling of t0.5 . Empirical and theoretical investigations proved our assumption that external water transport with the domino-like effect predominated over internal vascular transport. Biomimetic trichome wings simulated the domino-like water transport, highlighting the important role of flexibility wing arrays.