Osmotic stress from soil salinity impairs plant water uptake

Steps:

• Salt buildup in soil decreases soil water potential due to solutes.
• Water moves osmotically from higher potential in roots to lower in soil.
• This outflow dehydrates roots, further lowering root water potential.
• Sustained low water potential causes wilting and cell damage, killing the crop.

Why C is correct:

• Water potential (ψ) decreases with solute concentration (ψ_s = -iCRT); soil salt lowers ψ_soil, driving water out of roots (ψ_root > ψ_soil), exacerbating root dehydration.

Why the others are wrong:

• A: Salt raises, not lowers, solute effects; water moves to soil, not into it from roots.
• B: Soil ψ decreases, not increases; water moves out of roots, not into them.
• D: Water moves out of roots to soil, not into roots; root ψ decreases, not soil's effect directly.

Final answer: C