Phosphatase acting on L-galactose 1-phosphate (L-Gal 1-P), D-myoinositol 3-phosphate (D-Ins 3-P) and D-myoinositol 1-phosphate (D-Ins 1-P). Can also use beta-glycerophosphate (glycerol 2-P) and, to a lesser extent, D-galactose 1-phosphate (D-Gal 1-P), alpha-D-glucose 1-phosphate (a-D-Glc 1-P), D-mannitol 1-phosphate and adenosine 2'-monophosphate as substrates. No activity with D-fructose 1-phosphate (D-Fru 1-P), fructose 1,6-bisphosphate (Fru 1,6-bisP), D-glucose 6-phosphate (D-Glc 6-P), D-alpha-glycerophosphate (glycerol 3-P), D-sorbitol 6-phosphate and D-myoinositol 2-phosphate. The C1 phosphate position in a six-member ring substrate is important for catalysis. a myo-inositol phosphate + H2O = myo-inositol + phosphate beta-L-galactose 1-phosphate + H2O = L-galactose + phosphate Inhibited by LiCl or CaCl(2). Not inhibited by ascorbate. Optimum pH is 7.5. Polyol metabolism; myo-inositol biosynthesis; myo-inositol from D-glucose 6-phosphate: step 2/2. A number of isoforms are produced. According to EST sequences. Strongly expressed in photosynthetic tissues. Expressed in pistil and seed endosperm. Detected in globular to heart stage embryos. No visible phenotype, but reduced myoinositol and ascorbate levels. Belongs to the inositol monophosphatase superfamily.