Abstract: The effects of different concentrations of NaCl solution (0, 30, 60, 90, 120 and 150 mmol·L^-1) on the growth, biomass, leaf relative water content, root activity, root membrane permeability, osmotic adjustment and protective enzyme activity of Isatis indigotica seedlings (cv. Dinglan No.1) were assessed to determine the response of growth and physiological traits associated with resistance to salt stress after 14 days of exposure. Plant height, root length, root dry weight and leaf dry weight of I. indigotica seedlings under NaCl treatment were significantly reduced compared with the control (no salt). Reductions were greater under higher salt concentrations. As NaCl concentration increased leaf relative water content and root activity declined while root membrane permeability and leaf proline content increased. Superoxide dismutase (SOD) and peroxidase (POD) activity, malondialdehyde (MDA) content and rates of tissue autoxidation (RAD) all initially increased at lower salt levels and then declined. However seedling growth was not significantly inhibited under salt stress and root activity showed no obviously decrease. Malondialdehyde and proline content, SOD and POD activity were not affected by NaCl concentration <90 mmol·L^-1. This study showed that I. indigotica seedlings had some tolerance to low salt stress.

Key words: Isatis indigotica, salt tolerance, seedling growth, root activity, physiological responses