A synthesis of stomatal sensitivity to ABA across species and experiments

Significant effort has been put into understanding the role of abscisic acid (ABA) on stomatal response to water stress. However, the parametrization of ABA controls in current models of stomatal conductance ([Formula: see text]) remains challenging. Here, we synthesized current literature that quantifies ABA relation with [Formula: see text], water potential (Ψ), or both, across various experimental settings. We compiled a total of 242 datasets covering 60 plant species, with 193 observation sets linking [Formula: see text] and ABA and 138 observation sets linking Ψ and ABA. Ψ was measured in either the leaf, stem, or root, as reported in the corresponding studies. We examined different fitting functions to approximate the relation between Ψ and ABA, and [Formula: see text] and ABA. Statistical correlations were used to determine the best fit of [Formula: see text] vs ABA and Ψ vs ABA relationships, and to exclude datasets with poor correlations. No statistically significant differences were found between stomatal sensitivity to ABA (β, unitless) and biome type or the source of ABA (Kruskal-Wallis, P > 0.05). Statistical differences were found between β and experimental conditions (Kruskal-Wallis, P < 0.05), likely due to observational uncertainties. The overall distribution of β in all classifications suggests a typical sensitivity range (β) of 0.21 - 21.59 (median 1.87). These findings can be used to guide the development and evaluation of mechanistic models of [Formula: see text], providing realistic parameterizations of the links between ABA and stomatal closure.