Abstract: Seedlings of Isatis indigotica from five localities [Baoding, Hebei (HB); Baotou, Inner Mongolia (NB); Tie ling, Liaoning (LT); Bozhou, Anhui (AH); Binzhou, Shandong (SB)] were used as research materials, to investigate the seed germination and seedling growth of I. indigotica subjected to pure water (0 mmol·L^-1 NaCl) or three concentrations of NaCl solution (0, 50, 100, 150 mmol NaCl·L^-1). Salt tolerance among the five populations differed significantly. In general, the germination rate, germination potential, germination index and vitality index decreased with increase in NaCl concentration. NaCl at 50 mmol·L^-1 promoted the fresh weight, hypocotyl length and radicle length of I. indigotica seedlings from the HB and SB localities. The same three traits were significantly decreased in seedlings from all five localities under 100 mmol·L^-1 NaCl stress, and malondialdehyde (MDA) concentration increased greatly. The fresh and dry weights of leaf laminae and roots of I. indigotica seedlings from LT and AH localities area were decreased under salt stress at 150 mmol·L^-1 NaCl.With increasing NaCl concentration, the activities of superoxide dismutase (SOD) and peroxidase (POD) and proline contents of I. indigotica seedlings from the five localities increased to a peak at 100 mmol·L^-1 NaCl, with values decreasing somewhat at the 150 mmol·L^-1 NaCl concentration. From a comprehensive appraisal of membership function method, the salt resistance of I. indigotica seeds from the five different localities was ranked: HB>SB>LT>NB>AH.

Key words: Isatis indigotica, salt stress, seed germination, physiological characteristics, membership function method