Design of a unidirectional water valve in Tillandsia

Abstract

The bromeliad Tillandsia landbeckii thrives in the Atacama desert of Chile using the fog captured by specialized leaf trichomes to satisfy its water needs. However, it is still unclear how the trichome of T. landbeckii and other Tillandsia species is able to absorb fine water droplets during intermittent fog events while also preventing evaporation when the plant is exposed to the desert's hyperarid conditions. Here, we explain how a 5800-fold asymmetry in water conductance arises from a clever juxtaposition of a thick hygroscopic wall and a semipermeable membrane. While absorption is achieved by osmosis of liquid water, evaporation under dry external conditions shifts the liquid-gas interface forcing water to diffuse through the thick trichome wall in the vapor phase. We confirm this mechanism by fabricating artificial composite membranes mimicking the trichome structure. The reliance on intrinsic material properties instead of moving parts makes the trichome a promising basis for the development of microfluidics valves.

Idioblasts and peltate hairs as distribution networks for water absorbed by xerophilous leaves

“…Capparis odoratissima leaves immersed in water increased in weight at a rate of 0.30 mg cm −2 h −1 , which is approximately seven times greater than rates of epidermal evaporation. The rate of water absorption by C. odoratissima leaves, however, is four times lower than in the pubescent leaves of Tillandsia mullenbecki , which grows in the Atacama Desert in Chile, and is entirely dependent on foliar uptake (Raux, Gravelle, & Dumais, 2020). Nevertheless, we estimate that 15 h continuous exposure of the leaves to surface moisture may result in a 50% increase in leaf water content.…”

“…Our results revealed a high hygroscopicity of the peltate hairs of C. odoratissima. Hygroscopic peltate hairs have been reported in some angiosperm species (Bickford, 2016;Eller et al, 2016;Grammatikopoulos & Manetas, 1994;Pina, Zandavalli, Oliveira, Martins, & Soares, 2016;Vitarelli et al, 2016), with the best studied being epiphytic bromeliads (Benz & Martin, 2006;Benzing, 1976;Benzing et al, 1978;Benzing & Burt, 1970;Ohrui et al, 2007;Raux et al, 2020). While a trade-off between epidermal evaporation and water entrance from the atmosphere might exist, in C. odoratissima, this trade-off favours the uptake of water from the trichomes of the abaxial surface, and from the idioblast tips when water condenses in the adaxial surface.…”

Harvesting water from unsaturated atmospheres: deliquescence of salt secreted onto leaf surfaces drives reverse sap flow in a dominant arid climate mangrove, Avicennia marina

“…How might leaves access water that accumulates in saline solutions? Depending on physico‐chemical characteristics of both the leaf surface and the solution, leaf surfaces can absorb surface water and dissolved solutes by diffusion across the cuticle (Kerstiens, 2006), stomata (Eichert et al ., 1998; Burkhardt et al ., 2012) and through epidermal structures such as trichomes (Raux et al ., 2020; Schreel et al ., 2020), scales (Wang et al ., 2016) and hydathodes (Martin & von Willert, 2000) that facilitate diffusion across leaf surfaces (Fernandez et al ., 2017). Deliquescence plays critical roles in beneficial uptake of fertilisers applied to leaves (Fernandez & Eichert, 2009; Burkhardt, 2010) and in deleterious uptake of aerosols such as pollutants (Burkhart & Eiden, 1994; Burkhardt et al ., 2018) and salt spray (Burkhardt et al ., 2012) that become deposited on leaves of sensitive species.…”

Asymmetric water transport in dense leaf cuticles and cuticle-inspired compositionally graded membranes

“…Directional transport is ubiquitous in natural organisms, which use this mechanism for water collection and retention 1 , 2 . Asymmetric transport is also of great technological relevance, in applications that range from water harvesting 3 to the separation of chemicals 4 , 5 to functional clothing 6 .…”