Where do leaf water leaks come from? Trade‐offs underlying the variability in minimum conductance across tropical savanna species with contrasting growth strategies

Abstract

Summary Plants continue to lose water from their leaves even after complete stomatal closure. Although this minimum conductance (gleaf‐res) has substantial impacts on strategies of water use and conservation, little is known about the potential drivers underlying the variability of this trait across species. We thus untangled the relative contribution of water leaks from the cuticle and stomata in order to investigate how the variability in leaf morphological and anatomical traits is related to the variation in gleaf‐res and carbon assimilation capacity across 30 diverse species from the Brazilian Cerrado. In addition to cuticle permeance, water leaks from stomata had a significant impact on gleaf‐res. The differential pattern of stomata distribution in the epidermis was a key factor driving this variation, suggesting the existence of a trade‐off between carbon assimilation and water loss through gleaf‐res. For instance, higher gleaf‐res, observed in fast‐growing species, was associated with the investment in small and numerous stomata, which allowed higher carbon assimilation rates but also increased water leaks, with negative impacts on leaf survival under drought. Variation in cuticle structural properties was not linked to gleaf‐res. Our results therefore suggest the existence of a trade‐off between carbon assimilation efficiency and dehydration tolerance at foliar level.

Leaf Cuticular Transpiration Barrier Organization in Tea Tree Under Normal Growth Conditions

“…However, no significant correlations were found between these three stomata parameters and the abaxial cuticular transpiration rates. Machado et al (2020) also observed that for evergreens there is no significant association between stomatal properties and leaf water leaks. Our data suggest that the variations in the abaxial cuticular transpiration rates from these eight tea germplasms likely resulted from other factors rather than stomatal characteristics ( Figure 4A ; Supplementary Figure S3 ).…”

“…Ew Ad : the adaxial eipcuticular waxes; Iw Ad : the adaxial intracuticular waxes; Ew Ab : the abaxial eipcuticular waxes; Iw Ab : the abaxial intracuticular waxes. Machado et al (2020) studied 30 different native tree species, including drought deciduous and evergreen, and found that residual stomatal transpiration had a significant impact on the minimum conductance; the stomata distribution pattern in the epidermis was a key factor determining the variation in minimum conductance. To exclude the stomatal effects on the cuticular transpiration rate measurement, in this study the stomata density, guard cell length, and guard cell pair width were measured from SEM images (Supplementary Figure S3A).…”

Elevated CO2 Modulates Plant Hydraulic Conductance Through Regulation of PIPs Under Progressive Soil Drying in Tomato Plants

“…Thereby, under mild drought stress conditions, plants still possessed favorable leaf and root hydraulic properties, which could be able to minimize the risk of excessive dehydration via a coordinated balance between leaf transpiration and water transport from root to leaf, consistent with the previous findings ( Brodribb and Holbrook, 2004 ; Creek et al, 2018 ). Moreover, stomatal properties (e.g., stomatal size and density) are responsible for leaf water leak even when stomata are fully closed, which have a great impact on plant water use strategies ( Machado et al, 2021 ). Dramatic higher stomatal density in flacca than in AC has been reported by Fang et al (2019) , which might explain the significant low K root accompanied by still relatively high E and K leaf in stressed flacca , representing an extensive hydraulic failure and dysfunction in the regulation of the plant water balance.…”

New calculations for photosynthesis measurement systems: what's the impact for physiologists and modelers?

“…A significant barrier for the broad scale adoption of the M2021 theory in gas exchange systems is the necessity to measure g cw for which the best methods are still debated (Boyer, 2015a;Duursma et al, 2019;Márquez et al, 2022). Recent advances, emerging datasets and new methods for measuring g cw should accelerate the adoption of this new theory (Duursma et al, 2019;Machado et al, 2021;Márquez et al, 2022;Slot et al, 2021). Importantly, some aspects of gas exchange calculations are still uncertain and could change in the future.…”