text: Magnesium is the most abundant free cation in plant cytosol, is the central atom in chlorophyll and offers itself as a bridging ion for the aggregation of ribosomes in plants. Even small changes in the concentration of magnesium in plant cytosol or chloroplasts can drastically affect the key enzymes present in the chloroplasts. It is most commonly used as a co-factor in eukaryotes and functions as an important functional key in enzymes like RNA Polymerase and ATPase. In phosphorylating enzymes like ATPase or kinases and phosphates, magnesium acts as a stabilizing ion in polyphosphate compounds due its Lewis acidity. Magnesium has also been noted as a possible secondary messenger for neural transmissions. Magnesium acts as an allosteric inhibitor for the enzyme vacuolar pyrophosphatase (V-PPase). In vitro, the concentration of free magnesium acts as a strict regulator and stabilizer for the enzyme activity of V-PPase.