Water channel required to facilitate the transport of water across cell membrane. Highly expressed in roots and at lower levels in anthers and silks. By nitrate in roots. Expressed in roots with a circadian rhythm showing an increase at the end of the night period, a peak during the first part of the light period and then a decrease. Aquaporins contain two tandem repeats each containing three membrane-spanning domains and a pore-forming loop with the signature motif Asn-Pro-Ala (NPA). Belongs to the MIP/aquaporin (TC 1.A.8) family. PIP (TC 1.A.8.11) subfamily.