The role of magnesium in photosynthesis

Photosynthesis takes place in chloroplasts. Chlorophyll is the most abundant pigment involved in the light harvesting and the tetrapyrrole ring of chlorophylls, called chlorine, is similar to heme but contains Mg2++ chelated to the nitrogen atoms of the rings.

Photosynthesis strongly depends on sufficient Mg2++ supply, reduction of CO2 assimilation is often on Mg2++ deficient plants. Perhaps the most important single biological role of magnesium is in the formation of chlorophyll and the utilization of radiant energy in photosynthesis.

Magnesium ions are inserted into the chlorine ring through the action of a chelatase enzyme. Without the enzyme, magnesium could not combine with chlorins.
The role of magnesium in photosynthesis