Effects of exogenous silicon on melon seed germination and the growth of seedlings under NaCl stress

The effects of exogenous silicon on the growth of melon under salt stress were investigated.Seedlings of two melon cultivars(Xueli No.1and Longqinyinmi)with different salt tolerance were grown with 125mmol/L NaCl stress Exposure to 125mmol/L NaCl stress significantly inhibited melon seed germination.Compared with control,treatments with 0.5-1.0mmol/L exogenous silicon significantly increased seed germination rate,germination energy,germination index,alpha-amylase activity and water absorption and the treatment with 0.75 mmol/L exogenous silicon performed best.In addition,melon seedlings with 0.25-1.00mmol/L silicon exposed to 125 mmol/L NaCl had significantly increased plant height,leaf area,chlorophyll content,shoot dry weight and root dry weight,compared to controls.Treatment with 0.50mmol/L was optimal for Longqinyinmi,while 0.75mmol/L gave best results for Xueli No.1.These results indicate that exogenous silicon concentration from 0.50mmol/L to 0.75mmol/L can promote melon seed germination by enhancing alpha-amylase activity and water absorption,and promote seedling growth by increasing chlorophyll content and photosynthesis capacity under salt stress.When the silicon concentration was more than 1.25mmol/L,there was no effect on the seed germination and growth of seedlings under salt stress.