Which nutrient is primarily linked to the development of chlorophyll and thus photosynthesis?

Magnesium is essential for the development of chlorophyll, the green pigment found in plants that is crucial for photosynthesis. Chlorophyll absorbs light energy, primarily from the sun, allowing plants to convert carbon dioxide and water into glucose and oxygen. The presence of magnesium as a central atom in the chlorophyll molecule is what enables this biochemical process. Therefore, without adequate magnesium, plants can exhibit symptoms of chlorosis, which reflects their inability to produce sufficient chlorophyll, ultimately hindering photosynthesis.

Calcium plays a vital role in plant structure and growth but does not have a direct link to chlorophyll production. Iron is also significant because it is involved in various enzymatic processes and is necessary for the formation of chlorophyll, but it is magnesium that is specifically required for the chlorophyll molecule itself. Nitrogen is important for overall plant health and is a component of amino acids and proteins, but it does not play a direct role in the development of chlorophyll specifically, although it is involved in the overall growth and vigor of the plant.

Thus, magnesium is the nutrient that is primarily linked to chlorophyll development and, consequently, photosynthesis, making it the correct answer to the question.