Involved in responses to osmotic stress and abscisic acid (ABA). May act as a positive regulator of ABA signaling during germination and seedling development under stress. Expressed in the root elongation zone, stele, root cap, embryo vascular system, leaf axilar buds, silique abscission zone and guard cells. By salt and ABA treatments. No visible phenotype under normal growth conditions, but mutant seedlings show reduced root elongation under salt stress and increased germination rates under osmotic stress and exogenous ABA treatments.