Name the atmospheric gas used by plants to make proteins.

Nitrogen is an essential macronutrient needed by all plants to thrive. In plants much of the nitrogen is used in chlorophyll molecules which are essential for photosynthesis and further growth. It is needed for the production of amino acids which make up proteins. Nitrogen often comes from fertilizer application and from the air. Plants cannot use nitrogen in the gaseous form so it therefore needs to be turned into either nitrate or ammonium before it can be utilised by the plant. This can be done through nitrogen fixation.