Effect of salicylic acid applied through rooting medium on drought tolerance of wheat

An experiment was conducted to assess whether exogenously applied SA through the rooting medium could mitigate the adverse effects of water stress on plant growth, photosynthesis and nutrient status of two wheat genotypes. For this purpose, salicylic acid @ 0, 5, and 10 mg L-1 was applied through the rooting medium to plants of two wheat lines growing in plastic beakers (250 mL) filled with Hoagland's nutrient solution containing 0 or 19% PEG8000 to represent two water regimes of control (0 MPa) and -0.6 MPa respectively. Different levels of SA applied through the rooting medium increased photosynthetic rate in both cultivars under non-stress conditions but only in S-24 under water stress conditions. Exogenous application of 5 or 10 mg L-1 SA caused an increase in stomatal conductance, transpiration rate, and sub-stomatal of water stressed plants of cv. S-24 whereas it was true for draughted plants of MH-97 only when 5 mg L-1 SA applied. Cultivar S-24 was generally higher in N and P contents of shoot and root than that in genotype MH-97 under both normal and water stress conditions. A decrease in shoot and root N contents of both genotypes and shoot and root P contents of genotype S-24 only was observed in stressed plants when 5 mg L-1 of SA was applied through the rooting medium, whereas the same was true for root P and shoot Ca2+ contents in the non-stressed plants of both cultivars. Application of salicylic acid through the rooting medium significantly reduced the root K+ of two cultivars under both normal and water deficit conditions. Although, exogenously applied SA through the rooting medium had growth promoting effects under non-stress conditions, it did not mitigate the adverse effects of drought stress on growth of both cultivars, though genotype MH-97 showed some recovery under water stress conditions.