Effects of Ionic Components of Saline Water on Irrigated Sunflower Physiology

The characteristics of ions in saline water can be significantly different along the water salinity gradient. The physiologic processes of plants that are irrigated with this kind of water are remarkably influenced. Based on the field sampling data, the chemical components of irrigation water were studied, and their influence on sunflower nutrient uptake, water content, and dry weight were evaluated. The results demonstrated that irrigation water salinity was mainly controlled by Na, SO4, Mg, and Cl concentrations and the ionic characteristics changed as soon as water becomes saline. The concentrations of Na, Ca, Mg, and N in sunflower leaves changed slightly with increasing irrigation salinity, whereas the concentration of leaf C decreased steadily. The ions in irrigation water had significantly different effects on leaf nutrient uptake. The Ca and Cl concentrations in irrigation water significantly influenced the Ca-related ionic exchange and C- and N-assimilation processes in sunflower leaves. The water content in the stem rose positively with irrigation salinity, whereas we observed little response in the leaves, fruits, and roots, although they were all mainly affected by the concentrations of Ca, Cl, Na, NO3, and SO4 in irrigation water. The biomass in leaves, stems, flower discs, and seeds all significantly reduced with irrigation salinity increase, and a loss of about 25% in stem biomass was detected. The concentrations of Na, Ca, Mg, K, Cl, and SO4 in irrigation water influenced the dry weight of different organs. The results presented here demonstrate that the ionic effects of irrigation water on plant physiologic processes are complex, which is concerning in terms of improving plant salt tolerance and managing saline water resources.