Base water potential but not hydrotime predicts seedling emergence of Medicago sativa under water stress conditions

We determined the hydrotime model parameters of 10 alfalfa seed lots by incubating seeds at various water potentials in the laboratory. Meanwhile, seedling emergence under drought and salinity conditions in a greenhouse pot experiment, and seedling establishment in the field were determined. Correlation analysis was utilized to detect the relationship between hydrotime model parameters and seedling emergence under water stress conditions. The germination percentage did not differ significantly among seed lots when seeds were incubated at −0.1 MPa, while it differed significantly among seed lots at water potentials of −0.3 and −0.6 MPa. Compared to control conditions, drought and salinity decreased seedling emergence to different extents, depending on seed lots. Seedling emergence in the field differed significantly among seed lots and ranged from 30% to 80%. Ψ(b(50)) showed a significant correlation with seedling emergence under various conditions and with seedling establishment in the field, while no correlation was observed between θ(H), σ(φb) and seedling emergence and establishment. These results suggest that Ψ(b(50)) can be used to rank the vigor of alfalfa seed lots and thus predict seedling emergence and establishment under water stress conditions.