Leaf surface structures enable the endemic Namib desert grass Stipagrostis sabulicola to irrigate itself with fog water

Abstract

The Namib grass Stipagrostis sabulicola relies, to a large degree, upon fog for its water supply and is able to guide collected water towards the plant base. This directed irrigation of the plant base allows an efficient and rapid uptake of the fog water by the shallow roots. In this contribution, the mechanisms for this directed water flow are analysed. Stipagrostis sabulicola has a highly irregular surface. Advancing contact angle is 988 + 58 and the receding angle is 568 + 98, with a mean of both values of approximately 778. The surface is thus not hydrophobic, shows a substantial contact angle hysteresis and therefore, allows the development of pinned drops of a substantial size. The key factor for the water conduction is the presence of grooves within the leaf surface that run parallel to the long axis of the plant. These grooves provide a guided downslide of drops that have exceeded the maximum size for attachment. It also leads to a minimum of inefficient drop scattering around the plant. The combination of these surface traits together with the tall and upright stature of S. sabulicola contributes to a highly efficient natural fog-collecting system that enables this species to thrive in a hyperarid environment.

Optimal Design of Permeable Fiber Network Structures for Fog Harvesting

“…[9][10][11][12][13][14][15][16][17] The Namib desert beetle (Stenocara gracilipes) survives by drinking fog water that it collects on its wing case. 10,15 A grass (Stipagrostis sabulicola) in the same region employs an anisotropic microstructure on its thin long leaves to direct water droplets towards its roots.…”

“…10,15 A grass (Stipagrostis sabulicola) in the same region employs an anisotropic microstructure on its thin long leaves to direct water droplets towards its roots. 16 Tree canopies with slender leaves (Pinus radiata and Casuarina equisetifolia) also harvest water from fog ( Figure 1a). [11][12][13] Sticky spider webs 17 decorated with tiny water droplets collected from morning fog are a common sight (Figure 1b which captures the ratio of the response time of a particle to that of the surrounding flow.…”

Comparisons of stemflow and its bio-/abiotic influential factors between two xerophytic shrub species

“…The factors, such as a relatively large LNB (Levia et al, 2015;Li et al, 2016), a large LAB , a high LAI (Liang et al, 2009), a big BML (Yuan et al, 2016), a scale-like leaf arrangement (Owens et al, 2006), a small ILAB (Sellin et al, 2012), a concave leaf shape (Xu et al, 2005), a densely veined leaf structure (Xu et al, 2005), an upward leaf orientation (Crockford and Richardson, 2000), leaf pubescence (Garcia-Estringana et al, 2010) and the leaf epidermis microrelief (e.g., the non-hydrophobic leaf surface and the grooves within it) (Roth-Nebelsick et al, 2012), together resulted in retaining a large amount of precipitation in the canopy, supplying water for stemflow yield and providing a beneficial morphology that enables the leaves to function as a highly efficient natural water collecting and channeling system. According to the documentation at Flora of China (Chao and Gong, 1999;Liu et al, 2010) and the field observations in this study, C. korshinskii had more beneficial leaf morphology for stemflow yield than did S. psammophila, owing to a lanceolate and concave leaf shape, a pinnate compound leaf arrangement and a densely sericeous pressed pubescence (Fig.…”

Wettability, Polarity, and Water Absorption of Holm Oak Leaves: Effect of Leaf Side and Age

“…Such surface features together with their chemical composition (Khayet and Fernández, 2012) may lead to a high degree of roughness and hydrophobicity (Koch and Barthlott, 2009;Konrad et al, 2012). The interactions of plant surfaces with water have been addressed in some investigations (Brewer et al, 1991;Brewer and Smith, 1997;Pandey and Nagar, 2003;Hanba et al, 2004;Dietz et al, 2007;Holder, 2007aHolder, , 2007bFernández et al, 2011Fernández et al, , 2014Roth-Nebelsick et al, 2012;Wen et al, 2012;Urrego-Pereira et al, 2013) and are a topic of growing interest for plant ecophysiology (Helliker and Griffiths, 2007;Aryal and Neuner, 2010;Limm and Dawson, 2010;Kim and Lee, 2011;Berry and Smith, 2012;Berry et al, 2013;Rosado and Holder, 2013;Helliker, 2014). On the other hand, the mechanisms of foliar uptake of water and solutes by plant surfaces are still not fully understood (Fernández and Eichert, 2009;Burkhardt and Hunsche, 2013), but they may play an important ecophysiological role (Limm et al, 2009;Johnstone and Dawson, 2010;Adamec, 2013;Berry et al, 2014).…”