Concept:Water always moves passively via osmosis from an area of higher water potential to an area of lower water potential.
Formula:$$ \text{Flow: High } \Psi_w \rightarrow \text{ Low } \Psi_w $$
Solution:- Saline soil contains massive amounts of dissolved salt (solutes), which dramatically lowers the water potential (\( \Psi_{w} \)) of the soil.
- If the soil becomes saltier than the plant's own roots, then the water potential of the soil becomes lower than that of the root (\( \Psi_w \) of soil < \( \Psi_w \) of root).
- Consequently, water is drawn out of the roots and into the soil, causing lethal dehydration (exosmosis) in the plant.
Why other options are incorrect:- If \( \Psi_{w} \text{ soil} > \Psi_{w} \text{ root} \) (Option A), water would correctly flow into the plant, and it would not face dehydration. Note that Option B and C are mathematically the same statement, but based on the key, B is the direct phrasing describing the environmental cause.
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