title: Surface properties and physiology of Ulmus laevis and U. minor samaras: implications for seed development and dispersal.
abstract: Plant surface properties influence solid-liquid interactions and matter exchange between the organs and their surrounding environment. In the case of fruits, surface processes may be of relevance for seed production and dispersal. To gain insight into the relationship between surface structure, chemical composition and function of aerial reproductive organs, we performed diverse experiments with the dry, winged fruits, or samaras, of Ulmus laevis Pall. and Ulmus minor Mill. both at the time of full maturity (green samaras) and of samara dispersal (dry samaras). Samaras of both elm species showed positive photosynthetic rates and absorbed water through their epidermal surfaces. The surface wettability, free energy, polarity and solubility parameter were lower in U. laevis than in U. minor and decreased for dry samaras in both species. Ulmus laevis samaras had a high degree of surface nano-roughness mainly conferred by cell wall folds containing pectins that substantially increased after hydration. The samaras in this species also had a thicker cuticle that could be isolated by enzymatic digestion, whereas that of U. minor samaras had higher amounts of soluble lipids. Dry samaras of U. laevis had higher floatability and lower air sustentation than those of U. minor. We concluded that samaras contribute to seed development by participating in carbon and water exchange. This may be especially important for U. minor, whose samaras develop before leaf emergence. The trichomes present along U. laevis samara margin may enhance water absorption and samara floatability even in turbulent waters. In general, U. minor samaras show traits that are consistent with a more drought tolerant character than U. laevis samaras, in line with the resources available both at the tree and ecosystem level for these species. Samara features may additionally reflect different adaptive strategies for seed dispersal and niche differentiation between species, by favoring hydrochory for U. laevis and anemochory for U. minor.
authors.affiliation: Forest Genetics and Ecophysiology Research Group, School of Forest Engineering, Technical University of Madrid, Ciudad Universitaria, Madrid 28040, Spain.|Department of Plant Sciences, University of California Davis, One Shields Avenue, Davis, CA 95616, USA.
authors.forename: Paula
authors.initials: P
authors.lastname: Guzmán-Delgado
authors.affiliation: Forest Genetics and Ecophysiology Research Group, School of Forest Engineering, Technical University of Madrid, Ciudad Universitaria, Madrid 28040, Spain.
authors.forename: Victoria
authors.initials: V
authors.lastname: Fernández
authors.affiliation: Forest Genetics and Ecophysiology Research Group, School of Forest Engineering, Technical University of Madrid, Ciudad Universitaria, Madrid 28040, Spain.|Department of Biology, University of Utah, 257 South 1400 East, Salt Lake City, UT 84112, USA.
authors.forename: Martin
authors.initials: M
authors.lastname: Venturas
authors.affiliation: Forest Genetics and Ecophysiology Research Group, School of Forest Engineering, Technical University of Madrid, Ciudad Universitaria, Madrid 28040, Spain.
authors.forename: Jesús
authors.initials: J
authors.lastname: Rodríguez-Calcerrada
authors.affiliation: Forest Genetics and Ecophysiology Research Group, School of Forest Engineering, Technical University of Madrid, Ciudad Universitaria, Madrid 28040, Spain.
authors.forename: Luis
authors.initials: L
authors.lastname: Gil
mesh_terms: D058614:Seed Dispersal; D012639:Seeds / Q000502:physiology*; D013499:Surface Properties; D034403:Ulmus / Q000502:physiology*
keywords: cell wall; cuticle; pectins; plant surfaces; seed dispersal; water interactions