Hydrolyzes abscisic acid glucose ester (ABA-GE) which represents the predominant form of conjugated ABA (biologically inactive). No activity with beta-D-glucopyranosyl zeatin. The hydrolysis of ABA-GE in the endoplasmic reticulum (ER) forms free ABA and contributes to increase its cellular levels under dehydration conditions. ABA-GE hydrolyzing activity is enhanced by dehydration stress-induced polymerization into higher molecular weight forms. The ABA produced by BGLU18 contributes to the initiation of intracellular signaling as well as the increase in the extracellular ABA level. (+)-abscisic acid D-glucopyranosyl ester + H2O = 2-cis-(+)-abscisate + beta-D-glucose + H(+) Optimum pH is 6.0. Located in ER bodies. Seeds and hydathodes of rosette and cauline leaves. By ABA, dehydration, wounding and salt treatment. Reduced growth, yellow leaf, defective stomatal closure in the dark, increased transpirational water loss, sensitive response to dehydration, lower germination efficiency and decreased ABA levels. Polymerization into higher molecular weight forms displays diurnal fluctuation, similar to the ABA level. Belongs to the glycosyl hydrolase 1 family.