Answer
Increased soil salinity will cause water to stay in the soil since plants' roots would have a harder time absorbing it from the soil and may even cause them to excrete water. This would stress the plants, slowing or stopping growth by slowing or stopping water uptake.
Work Step by Step
Plants need water, as do all organisms, to fill their cells, for a solute in which the chemistry of life happens. Salty soils would inhibit or prevent water uptake, slowing or stopping all of a plant's vital processes.
