Why is magnesium essential to chlorophyll and photosynthesis?

Magnesium is essential to photosynthesis because it serves as the central atom of the chlorophyll molecule.123

Structurally, this magnesium atom is held within a porphyrin ring, a nitrogen-containing complex that forms the core of the pigment. This specific molecular arrangement allows chlorophyll to absorb light energy effectively. Once captured, this energy drives the chemical conversion of carbon dioxide and water into carbohydrates and oxygen, a process that provides the foundation for nearly all living systems.123

Because magnesium is a critical constituent of these pigments, it is classified as a macronutrient required by plants in substantial quantities to maintain healthy growth and development.4