Partitioning water potential and specific salt effects on seed germination of four grasses

In this study water potential (ψw) and the salt contribution to the osmotic component of ψw(ψw) of the germination solution were controlled separately to determine the interaction between specific salt and ψw effects on seed germination of Bouteloua curtipendula (Michx.) Torr., Cenchrus ciliaris L., Eragrostis lehmanniana Nees and Panicum coloratum L. Seeds were germinated in contact with solutions of NaCl, CaCl2, K2SO4, polyethylene glycol 8000 (PEG), and salt-PEG mixtures over the ψw range of 0 to −1·2 MPa. Ranking of specific salt effects on seed germination was not constant at different levels of ψw. CaCl2 was found to have the least detrimental, and often a positive, effect on total germination in all species and at all water potentials. The relative ranking of NaCl and K2SO4 effects was changed for two species when rank was based on germination response to isopotential salt-PEG mixtures.