Water channel required to facilitate the transport of water across cell membrane. Its function is impaired by Hg(2+). A number of isoforms are produced. According to EST sequences. Expressed in roots, above ground, ripening fruit, flower buds, green siliques and senescing leaves. The Asn-Pro-Ala (NPA) motifs may contribute to the formation of two hemipores that could generate a narrow channel. Belongs to the MIP/aquaporin (TC 1.A.8) family. PIP (TC 1.A.8.11) subfamily.