Response of Wheat to Static and Dynamic Non-Uniform Distribution of Salt in the Root Environment

Salt distribution is seldom uniform in field soil. Therefore, investigation on plant response to heterogeneous salinity is closer to actual field conditions. In this study, response of wheat (Tritivum aestivum L. cv. Rushan) to static and dynamic non-uniform salinity was investigated. Wheat root environment was divided into two identical parts containing 1.5 l nutrient solution. In non-uniform treatments, one side did not contain NaCl and the second side contained 40 or 80 mM NaCl while in uniform treatments, both sides were saline. In static non-uniform treatment, the location of NaCl-containing solution remained fixed at one side to the end of experiment while in dynamic treatment, the location of saline solutions was moved to the other side once after 3 or 6 d. At each salinity level, the loss of root and shoot biomass in the dynamic non-uniform salinity treatment with a 6-d displacement interval was lower than other salinity treatments. Among salinity treatments, plants at the D6-0/40 treatment accumulated the lowest Na and the highest K in their tissues. The highest leaf activity of catalase (CAT), ascorbate peroxidase (APX), and peroxidase (POX) and higher proline content at the D6-0/40 led to the lowest root ion leakage and leaf malonaldehyde (MDA) concentration. In contrast, plants at the uniform salinity treatment exhibited the highest sensitivity to salt stress and accumulated the highest amounts of Na in their tissues which was accompanied with greatest decrease in leaf chlorophyll and the severest oxidative injuries. The highest water use efficiency (WUE) was achieved at the control and D6-0/40 treatment. The dynamic non-uniform saline water irrigation can be used as a practical approach to enhance wheat productivity in salt-affected soils. Knowledge on response of roots to non-uniform salinities is of great importance to develop proper soil management strategies to optimize resource use in saline soils.