Water channel required to facilitate the transport of water across cell membrane. Probably involved in root water uptake. Its function is impaired by Hg(2+). A fuzzy intracellular localization is induced by salt (NaCl) treatment. Predominantly expressed in roots and green siliques. Also expressed at lower level above ground and in flower buds. Aquaporins contain two tandem repeats each containing three membrane-spanning domains and a pore-forming loop with the signature motif Asn-Pro-Ala (NPA). Ubiquitinated by RMA1, leading to proteasomal degradation. The phosphorylation at Ser-280 and Ser-283 is altered by salt (NaCl) and hydrogen peroxide H(2)O(2) treatments. Phosphorylation of Ser-283 is required for plasma membrane targeting. Belongs to the MIP/aquaporin (TC 1.A.8) family. PIP (TC 1.A.8.11) subfamily.