Osmotic stress from soil salinization reverses water flow

Steps:

• Repeated irrigation concentrates salts in soil as water is absorbed or evaporates, raising solute levels.
• Increased soil solutes lower soil water potential (more negative).
• Root water potential stays relatively higher than soil's.
• Water flows from higher (roots) to lower (soil) potential, exiting roots and causing dehydration.

Why C is correct:

• Water moves via osmosis from high to low water potential; soil potential decreases below root level, driving flow out of roots (reverse osmosis), starving cells of water per the water potential gradient law.

Why the others are wrong:

• A: Root potential decrease would promote water entry, not exit, worsening uptake issues incorrectly.
• B: Root potential increase mismatches reality—roots typically maintain or lower potential to draw water, not raise it.
• D: Soil potential increase (less negative) would enhance water entry into roots, opposing salinization harm.

Final answer: C