An ecological perspective on water shedding from leaves

Abstract

Water shedding from leaves is a complex process depending on multiple leaf traits interacting with rain, wind and air humidity, and with the entire plant and surrounding vegetation. Here, we synthesise the current knowledge of the physics of water shedding with implications for plant physiology and ecology. We argue that the drop retention angle is a more meaningful parameter to characterise the water shedding capacity of leaves than the commonly measured static contact angle. The understanding of the mechanics of water shedding is largely derived from laboratory experiments on artificial rather than natural surfaces, often on individual aspects such as surface wettability or drop impacts. In contrast, field studies attempting to identify the adaptive value of leaf traits linked to water shedding are largely correlative in nature, with inconclusive results. We make a strong case for taking the hypothesis-driven experimental approach of biomechanical lab studies into a real-world field setting to gain a comprehensive understanding of leaf water shedding in a whole-plant ecological and evolutionary context.

Pitcher geometry facilitates extrinsically powered ‘springboard trapping' in carnivorousNepenthes gracilispitcher plants

“…The off-centre axis of bending restricts the possible direction of movement to the pure up–down pivoting that is essential for ‘springboard' trapping [ 12 ]. Impact-induced oscillations are not unique to N. gracilis lids, but occur in all leaves, where they aid water shedding (reviewed in [ 14 ]) and thereby the dispersal of contaminants and pathogen spores [ 15 ]. In contrast to the clean pivoting of the N. gracilis lid, most leaves show a complex mixture of flapping, bending and twisting [ 16 ].…”

Progression toward maximum leaf surface storage during the rainfall interception process

“…Upon impact, raindrops shatter on vegetative surfaces producing multiple, smaller residual drops, and these residual drops continue to fall to the ground or impact additional vegetative surfaces below before reaching the ground (Levia et al, 2019; Nanko et al, 2022; Papierowska et al, 2019). Additionally, a proportion of the smaller residual drops produced after raindrops shatter on vegetative surfaces can adhere to leaf surfaces contributing to the leaf surface storage (Lenz et al, 2022; Wohlfahrt et al, 2006; Xiong et al, 2019). Leaf surface storage is the maximum amount of water retained on a leaf divided by the all‐sided surface area of the leaf (Holder, 2013).…”

“…Leaf surface storage is the maximum amount of water retained on a leaf divided by the all‐sided surface area of the leaf (Holder, 2013). The water contributing to leaf surface storage can be lost to evaporation, absorbed into the leaf, or contribute to throughfall or stemflow as the smaller water drops on leaf surfaces coalesce to form larger water drops and move off the leaf (Cavallaro et al, 2022; Lenz et al, 2022; Nanko et al, 2013).…”

“…the smaller residual drops produced after raindrops shatter on vegetative surfaces can adhere to leaf surfaces contributing to the leaf surface storage (Lenz et al, 2022;Wohlfahrt et al, 2006;Xiong et al, 2019). Leaf surface storage is the maximum amount of water retained on a leaf divided by the all-sided surface area of the leaf (Holder, 2013).…”

Optical and chemical control of the wettability of nanoporous photoswitchable films

“…Interfacial properties such as wettability are fundamental features of surfaces. Wettability is crucial for many processes in nature [1][2][3] and for many technical applications, such as the separations of emulsions. [4][5][6] The wettability of a given surface is typically evaluated by (static) contact angle measurements, where often water is used as a probe liquid.…”