Ion and Water Uptake in Plants

Steps:

• Water enters root hair cells via osmosis, moving down its concentration gradient from soil to cell.
• Nitrate ions (NO3-) enter against their concentration gradient, requiring energy, so via active transport.
• The question order is nitrate ions first, then water, matching the row's sequence.
• Option A aligns: active transport for ions, osmosis for water.

Why A is correct:

• Active transport uses ATP to move ions like nitrates against gradients (definition: energy-dependent carrier proteins); osmosis is passive water diffusion through aquaporins down gradients.

Why the others are wrong:

• B: Diffusion is passive and unsuitable for nitrates against gradients.
• C: Diffusion fails for nitrates; active transport doesn't apply to water's passive movement.
• D: Osmosis can't transport charged ions like nitrates; diffusion isn't primary for water here.

Final answer: A