The significance of the nitrogen cycle for plants lies in its role in transforming nitrogen from the atmosphere into forms that plants can absorb and utilize, primarily nitrates and ammonium. Nitrogen is a crucial nutrient for plant growth, as it is a key component of amino acids and proteins, which are essential for various physiological functions. The nitrogen cycle involves processes such as nitrogen fixation, nitrification, and denitrification, which ensure the availability of nitrogen in ecosystems, thereby supporting plant health and productivity.