Chlorophyll and magnesium are related because the chlorophyll molecule contains a magnesium ion. Green plants depend on chlorophyll for photosynthesis and magnesium is needed for chlorophyll production. Therefore, this element is an essential nutrient for green plants. In the process of photosynthesis, green plants use the energy of sunlight to synthesize glucose from water and carbon dioxide. Oxygen is produced as a byproduct of this reaction and therefore this process is largely responsible for maintaining oxygen levels on the planet.
The structure of chlorophyll allows it to play a crucial role in photosynthesis. Chlorophyll molecules are porphyrins, a group of compounds that share an arrangement of four nitrogen atoms with a space in the center that allows them to incorporate a metal ion that can bind to nitrogen atoms. This formation exists in chlorophyll molecules, and magnesium ions are found in the center. Porphyrins are usually very intense in color due to their tendency to absorb light at particular frequencies. Chlorophyll absorbs red and blue light very efficiently, letting green light reflect; this explains the color of the green plants.
There are a number of steps involved in photosynthesis, but it basically involves the transfer of electrons from water (H2O) to carbon dioxide (CO2), releasing oxygen (O2) from carbon dioxide, which allows the water is combined with carbon to make glucose (C6H12O6) – the simplest carbohydrate. The process is very complex, but it follows the equation: 6H2O + 6CO2 6O2 + C6H12O6. Glucose is the main source of energy for plant cells but also for animals, which obtain it directly or indirectly from plants. In a crucial step, the light absorbed by chlorophyll excites the electrons in the molecules, allowing them to transfer them to other molecules. Chlorophyll and magnesium bind in this step because magnesium helps the molecule absorb light and keeps the electrons in an excited state so that they can be transferred.
In addition to its role in chlorophyll, magnesium is also involved in the capture of carbon dioxide which provides carbon for the manufacture of glucose. It helps activate the enzyme ribulose-1,5-bisphosphate carboxylase oxygenase (RuBisCO), which catalyzes the incorporation of carbon dioxide into molecules involved in photosynthesis. This process is known as carbon dioxide fixation.
Chlorophyll production and the availability of magnesium in the soil are strongly related. Magnesium deficiency is manifested in plants by the yellowing of the leaves between the veins. This is known as chlorosis and tends to be seen first on older leaves, as the plant breaks down chlorophyll in older parts of the plant to maintain levels in areas of active growth. When soils are deficient in this element, they can be treated with a source of magnesium such as ground dolomitic limestone or magnesium sulfate, also known as Epsom salts.