Contents lists available at ScienceDirect Biotribology journal homepage: www.elsevier.com/locate/biotri Wetting Properties and Foliar Water Uptake of Tillandsia L. ☆ AnnaRoseC.Zambrano a, ⁎ ,VirgilioC.Linis a ,MariaRejaneJ.Nepacina a ,MarkLouieT.Silvestre a , Juanito Raphael F. Foronda b,c , Jose Isagani B. Janairo a,b,c a Biology Department, De La Salle University, 2401 Taft Avenue, Manila, 1004, Metro Manila, Philippines b Material Science and Nanotechnology Research Unit, Center for Natural Sciences and Environmental Research, De La Salle University, 2401 Taft Avenue, Manila 1004, Metro Manila, Philippines c iNano Physics Laboratory, De La Salle University, 2401 Taft Avenue, Manila 1004, Metro Manila, Philippines ARTICLEINFO Keywords: Foliar trichomes Foliar water uptake Liquid spreading and wetting property ABSTRACT Quantitative dimensional analyses of the wetting property of selected Tillandsia L. were conducted. The wett- abilityontheleafsurfacesofthree Tillandsia speciesandonehybridcultivarhassignifcantvariations(p < .05). Thisvariationisinfuencedbytheirabsorptive foliartrichomes.Thestructure,arrangementanddensityoftheir foliar trichomes on the leaf surfaces and the degree of corrugated trichome wings with variations on micro−/ nano-protrusion allow the liquids to increase its spreading and/or liquid repellency. Among the Tillandsia spe- cies, T. schiedeana Steudelhasthedensesttrichomes.Theaveragetrichomedensitiesareasfollows: T. schiedeana (61.20mm 2 ± 3.36) has the highest and T. Houston (T. stricta Sol. ex Sims T. recurvifolia Hook) hybrid (45.24mm 2 ± 5.93) has the lowest trichome density on the adaxial leaf surface; while T. schiedeana (63.55mm 2 ± 10.46) has the highest and T. xerographica Rohweder (40.66mm 2 ± 17.72) has the lowest trichome density found on the abaxial leaf surface (p < .0001). All examined Tillandsia exhibited foliar water uptake.Oneofthem, T. schiedeana hadsignifcantlygreaterincreaseinleafwatercontentupto115.9%followed by T. Houston (57.37%) > T. xerographica (36.63%) > T. caput-medusae E. Morren (35.91%). Based on the results of adhesion and surface free energy of the leaf surfaces, the desirable wetting properties of all four Tillandsia plants used in this study were determined. Among the four, T. schiedeana and T. caput medusae ex- hibited interesting liquid adhesion on the adaxial leaf surface which makes the two plants hydrophilic on this particularleafsurface.Ontheotherhand,thehighestwaterdropadherencetotheleafsurfaceisobservedin T. schiedeana which is necessary for its high foliar water uptake. In this study, it was proven that structure, ar- rangement and density of foliar trichomes found in Tillandsia afect the spreading of liquid and leaf surface wettability on their leaf surfaces which in turn improve the foliar water uptake of these plants. 1. Background Water is a signifcant resource that everyone of us need to survive yetroughlyoverabillionpeopleintheworldstilldoesnothaveaccess to reliable sources of this very important resource [1]. In some dry regions, however, fogs are common which can percolate into moisture that arid plants absorbed through their leaves [2]. Recently, fog col- lection has become an alternative source of water for agricultural, in- dustrial and domestic uses in these regions [3] and several emerging technologiesareenablinghumanpopulationslivingintheseregionsto capturefogfromtheatmosphere[4].Althoughtherearealreadywell- founded experimental designs and models available for fog collection, their methods and performance can still be improved. Knowledge gained from bio-inspired research, for instance, may serve as a guide- line for their rational redesigning with new features and engineering concepts. Such is the underlying motivation, why biological surfaces with their unique microstructures and wetting properties are used as bases for biologically inspired moisture-absorbing surfaces [5,6]. Wettability of surfaces have received tremendous interests both fromfundamentalandappliedpointsofview[7].Thispropertyplaysa signifcant role in many industrial processes, such as oil recovery, lu- brication, printing, and spray quenching [8–11]. Wettability studies usuallyinvolvethemeasurementofcontactanglesastheprimarydata, whichindicatesthedegreeofwettingwhenasolidmaterialsurfaceand liquid component interacts with each other [12]. In such cases, small contact angles (<90°) correspond to high wettability, while large https://doi.org/10.1016/j.biotri.2019.100103 Received 29 October 2018; Received in revised form 5 June 2019; Accepted 12 July 2019 ☆ 4th International Conference on BioTribology ⁎ Corresponding author. E-mail address: annarose.zambrano@gmail.com (A.R.C. Zambrano). Biotribology 19 (2019) 100103 Available online 13 July 2019 2352-5738/ © 2019 Elsevier Ltd. All rights reserved. T