Acid phosphatase activity with p-nitrophenyl phosphate (pNPP), D-myoinositol 1-phosphate (Ins(1)P1), phytic acid and Myo-inositol hexakisphosphate. Low or no activity with Glc-6-P and ATP. Confers shoot growth stimulation, enhanced salt and osmotic stress tolerance, and ABA insensitivity. May modulate ascorbic acid (AsA) levels by controlling the input of myoinositol into this branch of AsA biosynthesis. 1D-myo-inositol hexakisphosphate + H2O = 1D-myo-inositol 1,2,3,5,6-pentakisphosphate + phosphate a phosphate monoester + H2O = an alcohol + phosphate Binds 1 Fe cation per subunit. Binds 1 zinc ion per subunit. Optimum pH is 4.5. Homodimer. Expressed in roots, stems, cotyledons, leaves, flowers and siliques. Belongs to the metallophosphoesterase superfamily. Purple acid phosphatase family.