MAGNESIUM CYCLE: CHARACTERISTICS, COMPONENTS AND IMPORTANCE - ENVIRONMENT - 2025

The magnesium cycle is the biogeochemical process that describes the flow and transformation of magnesium between the soil and living beings. Magnesium is found in nature mainly in limestone and marble rocks. By erosion it enters the soil, where a part is available to be absorbed by plants, and through them reaches the entire trophic web.

A part of the magnesium in living beings returns to the soil when it is excreted from animals or by decomposition of plants and animals. In the soil, a fraction of magnesium is lost by leaching, and by runoff it reaches the oceans.

Image: Magnesium deficiency in a palm species. Author: Scot Nelson at flickr.com

The magnesium cycle is of great importance for life on the planet. Photosynthesis depends on it, as this mineral is an important part of the chlorophyll molecule. In animals it is important in the neurological and hormonal balance of the body. In addition to being the structural base of muscles and bones.

General characteristics

Magnesium is a chemical element, the symbol of which is Mg. Its atomic number is 12 and its mass is 24.305.

Pure magnesium is not available in nature. It is found forming part of the composition of more than 60 minerals, such as dolomite, dolomite, magnesite, brucite, carnalite and olivine.

Magnesium is a light, moderately strong, silvery-white, insoluble metal. It is the seventh most abundant element in the earth's crust and the third most abundant in seawater.

Magnesium constitutes 0.75% of the dry matter of plants. It is part of the chlorophyll molecule so it is involved in photosynthesis. It also participates in the synthesis of oils and proteins and in the enzymatic activity of energy metabolism.

Components

The global carbon cycle can be better understood if it is studied as two simpler cycles that interact with each other: magnesium in the environment and magnesium in living things.

Magnesium in environment

Magnesium is found in high concentrations in limestone and marble rocks. Most of the magnesium present in the soil comes from the erosion of these types of rocks. Another important input of magnesium to the soil today is fertilizers.

In the soil, magnesium occurs in three forms: in solution, in interchangeable form, and in non-interchangeable form.

Magnesium in soil solution is available in the form of soluble compounds. This form of magnesium is in balance with exchangeable magnesium.

The exchangeable magnesium is the one that is electrostatically adhered to the clay particles and organic matter. This fraction, together with the magnesium in soil solution, constitutes the Mg available to plants.

Non-exchangeable magnesium is found as a component of primary soil minerals. It is part of the crystal network that constitutes the structural base of soil silicates.

This fraction is not available to plants, because the degradation process of soil minerals occurs over long periods of time.

The magnesium contained in the soil is lost by leaching, being higher in areas with high rainfall and in soils with a sandy texture. Magnesium lost through leaching reaches the oceans to form part of seawater.

Another important loss of magnesium in the soil is the harvest (in agriculture). This biomass is consumed outside the production area and does not return to the soil in the form of excreta.

Magnesium in living things

Magnesium absorbed by plants from the soil is a cation with two positive charges (Mg ²⁺). Absorption occurs through two mechanisms: passive absorption and diffusion.

85% of magnesium enters the plant through passive absorption, driven by the transpiration stream or mass flow. The rest of the magnesium enters by diffusion, movement of ions from areas of high concentration to areas of lower concentration.

The magnesium assimilated by cells depends, on the one hand, on its concentration in the soil solution. On the other hand, it depends on the abundance of other cations such as Ca ²⁺, K ⁺, Na ⁺ and NH ⁴⁺ that compete with Mg ²⁺.

Animals obtain magnesium when they consume plants rich in this mineral. A part of this magnesium is deposited in the small intestine and the rest is excreted, to return to the soil.

In cells, the interstitial and systemic concentrations of free magnesium are regulated through its flux through the plasma membrane, according to the metabolic requirements of the cell itself.

This occurs by combining the mechanisms of muffling (the transport of ions to storage or extracellular spaces) and buffering (binding of ions to proteins and other molecules).

Importance

The magnesium cycle is an essential process for life. One of the most important processes for all life on the planet, photosynthesis, depends on the flow of this mineral.

The magnesium cycle interacts with other biogeochemical cycles, participating in the biochemical balance of other elements. It is part of the calcium and phosphorus cycle and is involved in their strengthening and fixation processes.

Importance of magnesium in living beings

In plants, magnesium is a structural part of the chlorophyll molecule, which is why it is involved in photosynthesis and in the fixation of CO ₂ as a coenzyme. In addition, it is involved in the synthesis of carbohydrates and proteins, as well as in the breakdown of carbohydrates into pyruvic acid (respiration).

In turn, magnesium has an activating effect on glutamine synthetase, an essential enzyme in the formation of amino acids such as glutamine.

In humans, and other animals, magnesium ions play important roles in coenzyme activity. It is involved in the formation of neurotransmitters and neuromodulators and in the repolarization of neurons. It also affects the health of the intestinal bacterial flora.

In turn, magnesium intervenes in the musculoskeletal system. It is an important part of the composition of bones. It intervenes in muscle relaxation and participates in the regulation of the heart rate.

References

1. Campo, J., JM Maass, V J. Jaramillo and A. Martínez Yrízar. (2000). Calcium, potassium, and magnesium cycling in aMexican tropical dry forest ecosystem. Biogeochemistry 49: 21-36.
2. Nelson, DL and Cox, MM 2007. Lehninger: Principles of Biochemistry Fifth Edition. Omega editions. Barcelona. 1286 p.
3. Quideau, SA, RC Graham, OA Chadwick, and HB Wood. (1999). Biogeochemical Cycling of Calcium and Magnesium by Ceanothus and Chamise. Soil Science Society of America Journal 63: 1880–1888.
4. Yabe, T. and Yamaji, T. (2011) The Magnesium Civilization: An Alternative New Source of Energy to Oil. Editorial Pan Stanford. Singapore. 147 pp.
5. Wikipedia contributors. (2018, December 22). Magnesium in biology. In Wikipedia, The Free Encyclopedia. Retrieved 15:19, December 28, 2018, from wikipedia.org.
6. Göran I. Ågren, Folke and O. Andersson. (2012). Terrestrial Ecosystem Ecology: Principles and Applications. Cambridge University Press.