Magnesium was discovered by Nehemiah Grew in 1695 by evaporating mineral waters in Epsom England. It was only in 1808 that Sir Humphrey Davy isolated the metal and identified it as magnesia oxide and termed it magnium. The metallic magnesium was first isolated by A. Bussy in 1828 and in 1883 the first metallic magnesium was produced electrolytically by Michael Faraday.
Magnesium is extremely important in the photosynthetic processes of the plant and is part of the elements in the chloroplast if the cell. The plants ability to fix carbon dioxide from atmosphere is rapidly impaired by deficiency in Mg since Mg forms an integral part of the chlorophyll molecule. If additional carbon dioxide is fed into a greenhouse, Mg should be increased in the solution in order to maximize the increased levels of carbon dioxide. Magnesium is very mobile in the plant so deficiency symptoms will not occur as fast as when calcium is deficient. Magnesium has the following functions in the plant:
- Serves as a co-factor in enzyme that activate phosphorylation processes
- Serves as a bridge between pyrophosphate structures of ATP or ADP and the enzyme molecule
- Stabilizes the ribosome particles in the configuration for protein synthesis
Magnesium is involved in various enzymatic roles but is different from those fulfilled by calcium and potassium. Plant content of magnesium varies between 0.15 – 1.00% on a dry weight basis. The magnesium content of tissue sap is 5-10 times that of calcium which just shows how mobile magnesium is in comparison to calcium. Magnesium is assimilated in the Mg2+ form only.