Spraying Silicon and/or Cerium Sols Favorably Mediated Enhancement of Cd/Pb Tolerance in Lettuce Grown in Combined Cd/Pb Contaminated Soil

A field experiment of foliar application of silicon sol, cerium sol and silicon-cerium composite sol of different concentrations on Lettuce in field mildly combined Cd/Pb contaminated soil, was conducted to study effects of the application on yield, quality, antioxidant enzymes (SOD, POD) activities and Cd/Pb absorption, and hence to determine optimum concentration of the silicon sols and cerium sols to be sprayed for relieving toxicity of Cd/Pb. Results showed that spraying silicon and cerium sols could promote growth of Lettuce, increase contents of vitamin C and soluble sugar, and reduce nitrite content, enhance activities of SOD and POD, and inhibit the absorption of Cd/Pb and decrease the content and accumulation of Cd/Pb in shoots and roots, and reduce the risk of Cd/Pb to human body through food chain, while spraying silicon-cerium composite sol of 0.50 g·kg-1 silicon sols (SiO2) and 0.20 g·kg-1 cerium sols (CeO2) was the most significant in effect.