Nitrate ions enter cells against their concentration gradient via active transport

Steps:

• Nitrate ions (NO3-) are charged solutes that require energy to move into cells.
• The process shown involves carrier proteins using ATP to transport ions uphill.
• This distinguishes it from passive movements like diffusion or osmosis.
• Plant root cells commonly use active transport for nutrient uptake like nitrate.

Why A is correct:

• Active transport uses ATP energy to move ions against electrochemical gradients, as defined in cellular biology for nutrient absorption.

Why the others are wrong:

• B: Diffusion is passive movement down a concentration gradient without energy.
• C: Osmosis is water movement across membranes via aquaporins, not ions.
• D: Translocation refers to long-distance transport in plants, like in phloem, not cellular entry.

Final answer: A