Variations in seed germination and salicylic acid protective effect between two cultivars of Astragalus membranaceus under drought and salt stress

To study the variations in seed germination between Astragalus membranaceus and A. membranaceus var. mongholicus under polyethylene glycol (PEG) and NaCl stresses, and to explore the differences in protective effects of salicylic acid (SA) for the two cultivars of A. membranaceus under severe PEG and NaCl stresses, we measured (1) the total germination percentage (TGP), germination energy (GE), vigor index (VI), shoot length (SL), root length (RL), shoot dry weight (SDW), and root dry weight (RDW) of two cultivars of A. membranaceus under gradually enhanced PEG and NaCl stresses; and (2) the differences in TGP of the two cultivars between application methods and concentrations of SA under severe PEG and NaCl stresses. Our results showed that all measurements of the two cultivars decreased with increasing stress intensity. Both low concentrations of PEG and NaCl can enhance seed germination in A. membranaceus. The VI in A. membranaceus var. mongholicus was higher than in A. membranaceus at -0.5 MPa PEG and -0.7 MPa NaCl stress levels (P<0.05). Soaking seeds with SA can enhance the TGP of of A. membranaceus. and A. membranaceus var. mongholicas The stress tolerance of A. membranaceus var. mongholicus was stronger than A. membranaceus. There were significant differences in seed performances between the two cultivars treated with SA. Soaking seeds with SA is was more effective than mixing seeds with SA.