$(i)$ In what form do plants utilize nitrogen?
$(ii)$ Why do they need nitrogen?

(N/A) $(i)$ Plants primarily utilize nitrogen in the form of nitrates $(NO_3^-)$ and nitrites $(NO_2^-)$,which are absorbed from the soil through their roots.
$(ii)$ Nitrogen is an essential element for plants because it is a fundamental component of amino acids,which are the building blocks of proteins. Additionally,it is required for the synthesis of nucleic acids $(DNA$ and $RNA)$,chlorophyll,and various enzymes necessary for plant growth and development.