Water channel required to facilitate the transport of water across cell membrane. Inactive in yeast cells. A number of isoforms are produced. According to EST sequences. Expressed in dividing cells and elongating regions of the root tips, emerging lateral roots, root steles, cotyledons, main veins of the rosette leaves, vascular tissues of the flower petals, stigma, stamens (anthers and filaments), pollen and the top and bottom (receptacle) of siliques. Aquaporins contain two tandem repeats each containing three membrane-spanning domains and a pore-forming loop with the signature motif Asn-Pro-Ala/Leu (NPA). Belongs to the MIP/aquaporin (TC 1.A.8) family. SIP (TC 1.A.8.10) subfamily.