Effects of silicon on plant growth,photosynthetic parameters and soluble sugar content in leaves of wheat under drought stress

Two wheat(Tritium aestivum L.) cultivars,Yangmai No.9(drought-sensitive) and Yumai No.18(drought-tolerant),were used to investigate the effects of exogenous silicon(Si) on growth parameters,photosynthetic and physiological characteristics of plant under drought stress simulated by PEG solutions(osmotic potential is about-0.589 MPa).The results indicated that the addition of soluble Si could significantly improve drought tolerance of wheat.Compared with the plants treated with PEG alone,the net photosynthetic rates of the leaves of drought-stressed wheat were significantly enhanced by the application of silicon. The treatment with 1.0 mmol/L Si was more effective in enhancing plant drought tolerance than the treatment with 0.1 mmol/L Si.Compared with control(with PEG alone), net photosynthetic rate(Pn),transpiration rate(Tr),water use efficiency(WUE) and stomatal limitation value(Ls) were more significantly enhanced,but stomatal conductance(Gs) and intercellular CO2 concentration(Ci) were significantly decreased by Si.Drought-stressed plants with Si applied had significantly greater fresh weight,dry weight and leaf soluble protein content compared with drought-stressed plants without Si applied.Moreover,Si application regulated the increase in soluble sugar contents which might induce a feedback-regulation of photosynthetic rate.