Plants source elements from soil versus air

Steps:

• Identify essential plant elements and their primary sources.
• Recall that macronutrients like nitrogen, magnesium, and iron are absorbed via roots from soil.
• Note carbon is a key component of CO2, fixed through photosynthesis from the atmosphere.
• Compare options to determine which doesn't come from soil.

Why A is correct:

• Carbon is obtained from atmospheric CO2 during photosynthesis, not soil, as per the process where plants convert light energy into glucose using the formula 6CO2 + 6H2O → C6H12O6 + 6O2.

Why the others are wrong:

• B: Iron is a micronutrient absorbed from soil to aid chlorophyll synthesis and enzyme function.
• C: Magnesium is a macronutrient from soil, central to chlorophyll structure for photosynthesis.
• D: Nitrogen is taken from soil as nitrates or ammonium ions for protein and DNA synthesis.

Final answer: A