Dephosphorylates and represses plasma membrane H(+)-ATPases (PM H(+)-ATPases, e.g. AHA1 and AHA2), thus influencing negatively plant growth and fitness. 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. Interacts with SAUR19. Slight increase in hypocotyl length (PubMed:24858935). Plants missing PP2C42/PP2C-D2, PP2C64/PP2C-D5, PP2C79/PP2C-D7, PP2C63/PP2C-D8 and PP2C68/PP2C-D9 exhibit an increased hypocotyl length, as well as an enhanced sensitivity to LiCl and media acidification (PubMed:24858935). Belongs to the PP2C family. Truncated N-terminus. Truncated N-terminus.