Accession difference in leaf photosynthesis, root hydraulic conductance and gene expression of root aquaporins under salt stress in barley seedlings

Soil salinity causes considerable losses of crop productivity. Barley (Hordeum vulgare) is one of the most salt-tolerant Gramineae crops. Previously, we found that net photosynthetic rate (A _n) was kept remarkably higher in the salt-tolerant barley accession OUE812 than in the salt-sensitive accession OUC613 after heading under salt stress due to the low level of salt accumulation in leaves. Here we grew seedlings in Hoagland solution with 100 mM NaCl (salt treatment) or without added NaCl (control), and compared A _n, stomatal conductance (g _s), salt accumulation in leaves, root hydraulic conductance and gene expression of root aquaporins between the accessions under salt stress for a few days. A _n, g _s and root hydraulic conductance of the plants with salt treatment decreased significantly in OUC613 compared to OUE812 with no accession difference in salt accumulation in leaves at 2 days after the onset of treatment (DAT). The reduction in root hydraulic conductance in OUC613 was caused by the reduction of the root hydraulic conductivity (Lp _r). Salt treatment also decreased the transcript levels of some plasma membrane intrinsic aquaporin genes (HvPIPs) in OUC613 and, on the contrary, increased those of some HvPIPs in OUE812, resulting in a large difference between OUC613 and OUE812 in the transcript levels at 2 DAT. The accession difference in HvPIPs expression and thus Lp _r was closely associated with the accession difference in A _n and g _s under the short-term salt stress.