Large differences in leaf cuticle conductance and its temperature response among 24 tropical tree species from across a rainfall gradient

Abstract

 More frequent droughts and rising temperatures pose serious threats to tropical forests. When stomata are closed under dry and hot conditions, plants lose water through leaf cuticles, but little is known about cuticle conductance (g min ) of tropical trees, how it varies among species and environments, and how it is affected by temperature.  We determined g min in relation to temperature for 24 tropical tree species across a steep rainfall gradient in Panama, by recording leaf drying curves at different temperatures in the laboratory.  In contrast to our hypotheses, g min did not differ systematically across the rainfall gradient; species differences did not reflect phylogenetic patterns; and in most species g min did not significantly increase between 25 and 50°C. g min was higher in deciduous than in evergreen species, in species with leaf trichomes than in species without, in sun leaves than in shade leaves, and tended to decrease with increasing leaf mass per area across species. There was no relationship between stomatal and cuticle conductance.  Large species differences in g min and its temperature response suggest that more frequent hot droughts may lead to differential survival among tropical tree species, regardless of species' position on the rainfall gradient.

Towards species‐level forecasts of drought‐induced tree mortality risk

“…Cochard et al (2021) simulated lethal embolism rates for a single oak tree species under a future Representative Concentration Pathways scenario (very high emissions, RCP8.5), attributing the driver to increasing vapour pressure deficit (please refer to below). This strong link to vapour pressure deficit is likely to reflect the assumed temperature sensitivity of cuticular conductance in their model, although support for a link between cuticular conductance and temperature is an important issue to resolve (please refer to Slot et al, 2021). Anderegg et al (2015) derived an empirical threshold between observed mortality in P. tremuloides and climatic water deficit to determine the likely future timescale of mortality based on coupled climate models.…”

Physiological trait networks enhance understanding of crop growth and water use in contrasting environments

“…The two-trait analysis of the High Plains Dry scenario revealed that nearly every simulation that did not include both deep roots and conservative stomata were largely failures, whereas the late season precipitation events and lower evaporation at the Central Plains site allowed for other alternative, albeit less successful, trait networks, e.g., high LAI coupled with high hydraulic safety and conservative stomata (Figs S24 & S26). Notably, the benefit of high LAI in this scenario was reversed when g min (minimum stomatal and cuticle conductance to water vapor) was increased from 3 mmol m -2 s -1 to 10 mmol m -2 s -1 , suggesting that stomatal “leakiness” may be an important trait to consider for future trait networks (Barnard and Bauerle 2013; Blackman et al 2019), particularly if stomatal leakiness increases at higher temperatures (e.g., under climate change), which has been reported for some species (Slot et al 2021).…”

Physiological trait networks enhance understanding of crop growth and water use in contrasting environments

“…The two‐trait analysis of the High Plains Dry scenario revealed that nearly every simulation that did not include both deep roots and conservative stomata were largely failures, whereas the late season precipitation events and lower evaporation at the Central Plains site allowed for other alternative, albeit less successful, trait networks, e.g., high LAI coupled with high hydraulic safety and conservative stomata (Figures and ). Notably, the benefit of high LAI in this scenario was reversed when g min (minimum stomatal and cuticle conductance to water vapour) was increased from 3 to 10 mmol m −2 s −1 , suggesting that stomatal “leakiness” may be an important trait to consider for future trait networks (Barnard & Bauerle, 2013; Blackman et al, 2019)⁠, particularly if stomatal leakiness increases at higher temperatures (e.g., under climate change), which has been reported for some species (Slot et al, 2021)⁠.…”