Can plants absorb nitrogen from the atmosphere to make proteins?

No, plants cannot absorb nitrogen directly from the atmosphere to make proteins. Most plants take up nitrogen from the soil in the form of nitrate (NO₃⁻) or ammonium (NH₄⁺) ions. Atmospheric nitrogen (N₂) is not usable by plants in its natural form. Instead, certain bacteria in the soil or in the root nodules of leguminous plants (like beans, peas, and clover) convert atmospheric nitrogen into ammonia through a process called nitrogen fixation. Plants then absorb these usable nitrogen compounds and use them to make proteins and other important molecules.