Magnesium is the element that is essential for the formation of chlorophyll in green plants. The capture of light energy from the sun is magnesium dependent. Magnesium is bound as the central atom of the Porphyrin ring of the green plant pigment chlorophyll. Magnesium is needed by plants to form chlorophyll which is the substance that makes plants green.Without magnesium sitting inside the heart of chlorophyll, plants would not be able to take nutrition from the sun because the process of photosynthesis would not go on. Because magnesium is contained in chlorophyll it is considered an essential plant mineral salt. Without chlorophyll, plants are unable to convert sunlight and carbon dioxide.