Patterns of leaf wettability along an extreme moisture gradient in western Patagonia, Argentina

The objective of this study was to investigate patterns of surface features of leaves related to susceptibility to wetness for plants along a strong precipitation gradient. Leaf wettability and droplet retention were examined for leaves of 37 species (representing 28 families) occurring in steppe, ecotone, and temperate rain forest habitats along a steep moisture gradient in northwestern Patagonia, Argentina. Morphological and structural characteristics of leaves significantly affected leaf surface wetness, and these characteristics varied between habitats. Typically, leaves had more stomata on abaxial than adaxial leaf surfaces ( P < 0.0001). Droplet retention and leaf wettability (theta) were negatively correlated (Spearman r = -0.694; P < 0.0001). Leaves in dry habitats tended to be less wettable and less likely to retain droplets on the leaf surface; however, overall differences were not significant. The presence of trichomes significantly reduced wettability ( P < 0.05). The high frequency and natural variability of wetting events in these and a great variety of other habitats, coupled with the large range in surface wettability among plant species and the potentially strong effects on photosynthesis, growth, and pathogen infections, suggest an important evolutionary avenue related to the dynamics of water on leaf surfaces.