Acts as negative regulator of abscisic acid (ABA) signaling for stomatal closure in leaves, and controls water loss during leaf senescence (PubMed:22007837, PubMed:22184656). Activated by the NAC029/NAP transcription factor during ABA signaling in senescing leaves (PubMed:22184656). Functions as negative regulator of osmotic stress and ABA signaling (PubMed:22198272). Acts as negative regulator of response to drought (PubMed:22829320). H2O + O-phospho-L-seryl-[protein] = L-seryl-[protein] + phosphate H2O + O-phospho-L-threonyl-[protein] = L-threonyl-[protein] + phosphate Binds 2 magnesium or manganese ions per subunit. By abscisic acid (ABA) (PubMed:22007837, PubMed:22198272). Induced during leaf senescence (PubMed:22007837). Induced by osmotic stress (PubMed:22198272). Delayed senescence. Increased sensitivity to abscisic acid (ABA). Belongs to the PP2C family.