Contact angle measurements and water drop behavior on leaf surface for several deciduous shrub and tree species from a temperate zone

Abstract

Key message Leaf CA measurement should take into account angle variation during measurement time. Leaf wettability of common deciduous forest plants is characterized by wetting contact angles ranging from 60° to 140° with a significant variation between species of the same family. Abstract Leaf wettability is an important phenomenon that has an influence on several processes such as the hydrological cycle, plant pathogen growth, or pollutant and pesticide absorption/deposition. The main objective of this research was to investigate the leaf wettability differences of 19 species (16 trees and 3 shrubs) of deciduous plants commonly occurring in Polish forests (temperate climate). The measurements were gathered as follows: 20 undamaged leaves were selected for each species and the wettability was determined by contact angle measurements with an optical goniometer CAM 100 using the sessile drop method. The contact angle was measured with 1-s intervals during 2 min from droplet deposition on adaxial and abaxial leaf surface. Laboratory analyses were completed during the summer of 2016 during full vegetation growth. A general CA decrease with time was observed on both leaf sides. The contact angle values ranged from 60° to 140° depending on species and leaf side. Differences between contact angle values at the beginning and the end of measurement reached 23.6° and engendered changes of wetting classes for some species. In many cases, no wettability class change was observed despite a CA lowering of 20°. The abaxial side was found to be the more repellent for 14 out of 19 species. Altogether, the leaves were classified from highly wettable to highly non-wettable, probably depending on the plant-survival strategy.

Spatial and Temporal Variability of Throughfall among Oak and Co-Occurring Non-Oak Tree Species in an Upland Hardwood Forest

“…Likewise, denser forest stands with more canopy layers have less throughfall than sparser stands or those with fewer canopy layers. At the individual tree level, species with glabrous leaf coatings shed water more easily than those with rough surfaces, reducing leaf interception and increasing throughfall [10,11]. Other leaf characteristics, such as orientation and shape, can influence the ability of individuals to shed or intercept rainwater [12,13].…”

Seasonal changes in morphology govern wettability of Katsura leaves

“…In this study, leaf samples were assumed to be air-pollutant free due to the high-air quality of Virginia Tech’s campus where they were collected. However, the contact angle and its hysteresis might be affected by the level of contamination [ 30 – 32 ], water temperature [ 20 ], tree species [ 33 ], and the position in the crown. In future, the effects of air pollution or position in the crown might be interesting questions.…”

Biological Flora of the British Isles:Aesculus hippocastanum

“…Despite the abundant wax, Papierowska et al. () found that, based on the angle of contact of water droplets, the adaxial surface of horse‐chestnut is “wettable” and the abaxial “highly wettable.” This is similar to that found in Acer pseudoplatanus and Betula pendula but in contrast to 14 of the 19 European deciduous species tested where the abaxial surface was the least wettable. Although high wettability may result in a film of water reducing gas exchange, the authors suggest that it also allows water droplets to spread out and quickly evaporate and so leaves quickly dry, reducing the time that pathogens have a moist surface to invade, and so lower the need for internal chemical defences.…”

“…Leaves have epicuticular wax containing large amounts of triterpenols and triterpenol esters including β-amyrin, a-amyrin, lupeol, friedelanol and friedelanone (Gülz, Müller, & Herrmann, 1992). Despite the abundant wax, Papierowska et al (2018) found that, based on the angle of contact of water droplets, the adaxial surface of horse-chestnut is "wettable" and the abaxial "highly wettable." This is similar to that found in Acer pseudoplatanus and Betula pendula but in contrast to 14 of the 19 European deciduous species tested where the abaxial surface was the least wettable.…”