| A sand cultivation experiment was conducted to study the effects of Zn2+ with different concentrations (10-6 mol·L-1, 10-5 mol·L-1, 10-4 mol·L-1, and 10-3 mol·L-1) and PEG-6000 (5%、10%、15%、20%、30%) on seed germination, seedling growth, osmotica accumulation, and active oxygen metabolism of Codonopsis pilosula, an authentic Chinese herbal medicine in Gansu province. The results showed that the low concentrations of Zn2+ and PEG could significantly enhance seed germination and seedling growth. With the increase of Zn2+ and PEG concentrations, the germination rate became decreased significantly, and seedling growth was inhibited. The lowest permeability threshold was -0.94 MPa. O2- production rate and H2O2 contents in leaf were increased dramatically. In addition, activities of superoxide dismutase, peroxidase, catalase, and ascorbate peroxidase went down after an initial increase. Contents of glutathione and ascorbic acid in leaf were decreased markedly. Levels of proline, soluble sugar and malonaldehyde contents in young seedling leaf went up significantly with the increase of Zn2+ and PEG concentrations. It was found that 10-6 and 10-5 mol·L-1 zinc salt could improve the drought tolerance capability of Codonopsis pilosula to moderate stress. 10-3 mol·L-1 zinc salt and drought stress caused the maximal damages. |