Objective  To determine the sodium silicate concentration that could effectively mitigate the autotoxicity stress, which is one of the main factors causing difficulties on continuous cropping and seriously economic loss, on melon farming.

  Method  Seedlings of Cucumis melo L. with two true leaves and one bud were used in this study. The 0.03 g·mL^-1 water extract of the plant was used to simulate the autotoxicity stress. Sodium silicate solutions at different concentrations (0, 1, 2, 4, 8, 16 and 32 mmol·L^-1) were added as treatments to determine the effectiveness in the stress alleviation through observations on the growth, plant height, root length, fresh weight, dry weight of shoot, stem diameter, and root surface area of the seedlings. Changes on chlorophyll fluorescence parameters of the seedlings were monitored as well for the analysis.

  Result  The imposed autotoxicity significantly inhibited the increases on seedling height and leaf area. In varying degrees, the Fv'/Fm', Y (Ⅱ), qP, and Y (NPQ) of the plants decreased, while NPQ and Y (NO) increased. However, the presence of sodium silicate at 4mM effectively reduced the stress with the Fv'/Fm', Y (Ⅱ), NPQ, qP, Y (NPQ), and Y (NO) as they became closer to or better than those of control.

  Conclusion  Appropriate exogenous silicon treatment appeared to enable the melon seedlings under autotoxicity stress to grow normally with a stable photosynthetic function.