Ecological and Physiological Analysis of Effect of Different Types of Sodium Salt Treatment on Winter Wheat Resistance to Drought

The effects of different concentrations of sodium salts(NaCl,Na2CO3,Na2SO4)on resistance of winter wheat(Triticum aestivum) seedlings to drought were studied to analyze physiological mechanism of winter wheat tolerance increase to drought by salt stress treatment.The 7-day-old seedlings grown in pots were irrigated with sodium salt of different concentrations(70 mM,135 mM,200 mM,270 mM)for 8 days,then were treated with drought stress for 12 days and rehydrated for 5 days.Then,the moisture content in the leaves and soil,the activities of catalase(CAT),peroxidase(POD) and superoxide dismutase(SOD),MDA content and proline content were measured in the fresh leaves obtained at the 4th day and 8th day after salt stress,4th day,8th day and 12th day after drought stress,and 5th day after rehydration.Results showed that during the drought stress process,the moisture content in the leaves and soil rapidly declined with no salt and lower concentration(70 mM) NaCl,Na2CO3,Na2SO4 treatments,but the moisture content in the leaves and soil declined slowly with treatment of higher salt concentration under drought stress.With drought stress for 6 days,the leaves of winter wheat with no salt treatment became welting and had higher content of MDA and proline and activity of SOD than that with higher salt concentration treatment.But the plants with treatment of higher sodium salt concentration grew very well under drought stress for 12 days,and had lower increase level in the content of MDA and activities of antioxidant enzymes than that with no salt treatment.The proline content in the leaves increased with drought stress,but the increase level decreased with the salt concentration increase.After rehydration for 5 days,there was an increase in leaf relative water content,decrease in the contents of MDA and proline,and activities of antioxidant enzymes in the leaves maintained high level.There were no significant differences in increase of winter wheat resistance to drought between different types of sodium salt treatments.This study indicates that salinity in the soil plays an important role in formation of drought resistance of winter wheat because the solute in the cell can increase solute potential and make winter wheat hold more water,reduce the drought stress on cells,make plant survive longer under drought stress.This study also suggests that determination of optimum salt concentration is the key for the use of salinity water irrigation to hold higher output.