What form does nitrogen gets taken up in plants? 

Nitrate

The correct answer is option 3. Nitrate.

In plants, nitrogen is primarily taken up in the form of nitrate (NO₃⁻) from the soil. Nitrate is the most common and preferred form of nitrogen for plant absorption. The nitrogen cycle involves the conversion of atmospheric nitrogen (N₂) into forms that plants can use. Nitrate is a water-soluble form that plants can easily absorb through their roots. Nitrogen can also be taken up in the form of ammonium (NH₄⁺) or, to a lesser extent, as amino acids or other organic nitrogen compounds. However, nitrate is the dominant form in most well-aerated soils.