‘Sneezing’ plants: pathogen transport via jumping-droplet condensation

Abstract

We show that condensation growing on wheat leaves infected with the leaf rust fungus, Puccinia triticina , is capable of spontaneously launching urediniospores off the plant. This surprising liberation mechanism is enabled by the superhydrophobicity of wheat leaves, which promotes a jumping-droplet mode of condensation powered by the surface energy released from coalescence events. We found that urediniospores often adhere to the self-propelled condensate, resulting in liberation rates of approximately 10 cm −2 h −1 for leaves infected with rust. Urediniospores were catapulted up to 5 mm from the leaf’s surface, a distance sufficient to clear the laminar boundary layer for subsequent dispersal even in gentle winds.

Dynamics of splashed droplets impacting wheat leaves treated with a fungicide

“…Winter wheat lines known to be susceptible to stem rust (Massey, and VA-135) were provided by the Griffey lab at Virginia Tech. Plants were propagated and inoculated as described in previous publications [17,18]. Mature leaves were detached from plants and used for experiments within 48 h. Figure 1 a and 1 b show an infected leaf and microscopic spores, respectively.…”

“…Spores forced into the air by an impacting raindrop can get dispersed by air vortices also generated from the impact [17]. More recently, it was discovered that naturally occurring dew cycles can also liberate spores from wheat leaves [18]. The mechanism is the coalescence-induced jumping of micrometric dew droplets [19], which can propel adhered spores several millimetres above the leaf surface to clear the boundary layer [18].…”

“…More recently, it was discovered that naturally occurring dew cycles can also liberate spores from wheat leaves [18]. The mechanism is the coalescence-induced jumping of micrometric dew droplets [19], which can propel adhered spores several millimetres above the leaf surface to clear the boundary layer [18]. For all of these rainsplash and condensation mechanisms, liberated spores can be carried by many kilometres in the wind after clearing the laminar boundary layer [8][9][10][11][12].…”

“…Wheat leaves exhibit a superhydrophobic surface wettability [20] comprised of micro/nano-scale surface roughness, which heavily influences the dynamics of impacting rain drops. For example, raindrops can easily splash or bounce from a superhydrophobic wheat leaf [17] and even dew droplets can spontaneously jump from the leaf upon naturally occurring coalescence events [18]. The dynamics of droplets impacting superhydrophobic surfaces has been widely studied [21][22][23][24][25][26][27][28][29][30][31][32][33].…”

Molecular and Topographical Organization: Influence on Cicada Wing Wettability and Bactericidal Properties

“…Many animal and plant surfaces have functionalities that would be desirable on engineered substrates and have become the focus of intense research. Insect wings are examples of surfaces that have evolved to exhibit a range of properties, including superhydrophobicity, [ 1–3 ] self‐cleaning, [ 4–6 ] droplet jumping, [ 1,4,7,8 ] optical reflectivity, [ 7,9 ] antifogging, [ 6 ] and antimicrobial activity. [ 10,11 ] These properties have been observed on the wings of cicadas, [ 1,2,7,12,13 ] butterflies, [ 14 ] dragonflies, [ 5,15 ] and damselflies.…”