Interactive Effect of Seawater and Growth Bioregulators on Water Relations, Abscisic Acid Concentration and Yield of Wheat Plants

Irrigation of wheat plants with seawater (10 and 25 %) led to a significant increase in free and bound ABA in leaves, especially at 25 %. The relative water content (RWC), particularly at 25 %, and water use efficiency of the seawater-irrigated plants were lower than those of the control. Grain pre-soaking in GA₃, IAA or ABA reduced the levels of accumulated ABA (free and bound) resulting from seawater irrigation. The stress imposed by seawater generally reduced yield and yield components of wheat plants, and the effect was more pronounced at the higher level of seawater (25 %). Furthermore, seawater treatments decreased the carbohydrate content and increased the protein content of the developing grains. The effect of seawater treatments on ion concentration in the developing grains was not consistent. The application of growth bioregulators appeared to mitigate the effect of seawater salinity stress on wheat productivity. Gibberellic acid gave the best effect. The economic yield (grain yield) had a strong positive correlation with RWC, water use efficiency for grain yield, water use efficiency for biomass, plant height, shoot fresh and dry weights, grain number/main spike, kernel weight and harvest index.