Plant Material and Growth Conditions.

The Columbia-0 (Col-0) accession of A. thaliana was used as the wild-type background. Experiments on seedlings were conducted using plants germinated and grown on 1/2 Murashige and Skoog (MS) media (pH 5.7 to 8) solidified with 1% Phyto-agar. Experiments on mature plants were conducted using plants grown in soil (Sunshine Mix #1) filled plastic pots incubated in a growth chamber (Conviron) under a 12 h–12 h light–dark cycle, a light intensity of 100 µmol m⁻² s⁻¹, a temperature of 22 °C, ambient [CO₂], and a relative humidity of 65%. To minimize the impact of environmental variation, all experiments were performed on plants grown in two identical growth chambers equipped with [CO₂] control.

ABA treatments in plate-based experiments were performed using a mesh (100 µm polyester) transfer method. Seeds were germinated on ½ MS agar plates overlaid with sterilized polyester mesh (100 µm). ABA treatments were initiated by transferring 8-d-old seedlings in mass to plates containing 50 µM ABA (Sigma cis/trans-ABA) or to plates containing vehicle control (Ethanol). ABA treatments on soil-grown plants were performed by spraying plants with 50 µM ABA diluted with 0.01% Silwet (in water) or with vehicle control. To assess treatment responses, leaf temperature was measured using an infrared thermal imaging camera (T650sc; FLIR).