Plants grown in phosphorusdeprived solutions often exhibit disruption of water transport due to reduction in root hydraulic conductivity (Lpr). To uncover the relationship between root Lpr and water perme ability coefficient (Pf) of plasma membrane and the role of aquaporins, we evaluated Pf of plasma membrane and also PIPtype aquaporin gene expression in tobacco (Nicotiana tabacum L.) plant roots after seven days Pdeprivation. The results showed significant reduction in sap flow rate (Jv) and osmotic root hydraulic conduc tivity (Lpro) in Pdeprived roots. These effects were reversed 24 h after Presupplying. Interestingly, the Pf of root protoplasts was 57% lower in Pdeprived plants compared with Psufficient ones. The expression of NtPIP1;1 and NtPIP2;1 aquaporins did not change significantly in Pdeprived plants compared with Psuffi cient ones, but the copy number of NtAQP1 increased significantly in Pdeprived plants. Pdeprivation did not change Lpro significantly in antisense NtAQP1 plants. Taken together, these findings suggest that Pdeprivation may play an important role in modulation of root hydraulic conductivity by affecting Pf in transcellular pathway of water flow across roots and aquaporins. Finally, we concluded that dominant water transport pathway under Pdeprivation was transcellular one.
