The Significance of Magnesium in Your Hydroponic Plants

Magnesium is required in significant amounts in your plants as it is needed everywhere inside and outside of plant cells. The reason plants are green is because of magnesium; this metal is at the center of every chlorophyll molecule and the green pigment in plants. Without the magnesium, the chlorophyll molecule falls apart and light energy is not captured in photosynthesis. Thus, plants cannot make their food and grow.

Magnesium is also involved wherever phosphorus is being used to transfer cellular energy; Mg stabilizes high-energy phosphates whenever they are being carried by molecules such as adenosine triphosphate (ATP), or guanosine triphosphate GTP.

Magnesium nutrition of plants is frequently overlooked and shortages will adversely impact plant growth. Many essential plant functions require adequate Mg supplies with the most visible being its role in root formation, chlorophyll, and photosynthesis. Many less obvious reactions are also dependent on an adequate supply of Mg. Using a supplement such as Cal-Mag as part of your feeding schedule provides immense benefits above and beyond what is discussed in this post. This review briefly summarizes some of the essential roles of Mg for plants.

Functions of Mg in Plant Metabolism

  • Chlorophyll formation
  • Photosynthesis
  • Transfer energy
  • Medicates Calcium and Potassium absorption
  • Maximize shoot growth
  • Carbohydrate Formation
  • Carbohydrate Partitioning
  • Functional nucleic acid and protein Biosynthesis
  • Functions as mobile ion
  • Resistance to unfavorable factors – drought, cryptogamic disease
  • Synthesis of amino acids

Literature Cited

Crop yield depends in large part on the availability and accessibility of Nitrogen in the soil. For optimal yield, the soil nitrogen must be available at critical periods of crop development, and in the form that is accessible for plant uptake and use. Ancillary crop nutrients can alter the plant’s ability to access and utilize nitrogen. Therefore, crop fertilization with magnesium should focus on its effect on nitrogen management. This conceptual review aims to assess the present state of knowledge regarding the importance of magnesium in fulfilling both objectives.

  1. Grzebisz ., 2013.,Crop response to magnesium fertilization as affected by nitrogen supply., Plant and Soil., Volume 368., Issue. 1., pp. 23-39

Under conditions of poor management, severe Mg deficiency is often observed in chestnut groves located on base-poor granites and schists, in NE Portugal. Many of the severe cases of Mg-deficiency are due to nutritional imbalances between Mg and a growth-stimulating nutrient, particularly nitrogen. In areas affected by Mg-deficiency sharp contrasts have been observed between chlorotic and symptom-free trees, particularly in young groves. A 20-years-old chestnut grove of a traditional Portuguese variety, Longal, was selected to study the influence of Mg-deficiency on several tree growth parameters, yield and chestnut quality. Trees were classified according to the intercostal yellowing chlorosis of their leaves into three categories: symptom-free, slight chlorosis, and acute chlorosis. There is a strong negative correlation between severity of chlorosis and foliar Mg concentration, tree growth parameters, chestnut production and fruit quality. The mean Mg concentration in leaves of symptom-free trees was 1.2 g kg−1, and the lowest value in green leaves was 0.85 g kg−1. Severe intercostal chlorosis was observed when the Mg concentration in leaves was less than 0.55 g kg−1. The N/Mg ratios increase with the severity of the deficiency, reaching values higher than 40 in the leaves of trees with more acute deficiency. Shortage of Mg causes reduced growth of chestnut trees, severe yield reduction, and lower nut caliber; nuts have lower levels of dry matter content and crude fat, but higher crude protein content:

  1. Portela, J. Ferreira-Cardoso, M. Roboredo and M. Pimentel-Pereira,1999. Influence of magnesium deficiency on Chestnut ( Castanea Sativa Mill.) yield and nut quality. Improved crop quality by nutrient management, developments in plant and soil sciences, volume 86, 4, 153-156

Magnesium deficiency of Pinus resinosa, P. Strobus, and P. Banksiana was studied in young forest plantations on light textured soils bordering the western and southwestern margins of the Adirondack province of New York.

The most prominent symptom of deficiency was a bright yellow discoloration of the tips of the current season’s needles, appearing in the fall and affecting the upper part of the tree most strongly. When the deficiency was severe, the chlorosis was followed by the death of the needle tips or premature loss of foliage. Gross reductions in shoot growth and needle length occurred only under extreme deficiency or when potassium deficiency accompanied lack of magnesium.

There is a well-established interaction between Mg and K, and high rates of the latter can intensify deficiency symptoms and reduce the Mg content of the crop. Field experiments strongly suggest that the induced Mg-deficiency from substantial rates of applied potash seldom reduces the yield of potatoes, cereals or sugar beet:

  1. R. J. Holmes, 1962. The magnesium requirements of arable crops, Journal of the Science of Food and Agriculture, Volume 13, Issue 11, pages 553–556.

Magnesium is an essential plant nutrient, but magnesium deficiency occurs fairly widely in Europe and North America, especially on light soils. In Great Britain, this is known to be so for many horticultural crops, although information on deficiencies in plants is limited.

Deficiency symptoms are often seen in cereals, and sugar beet are usually transient, and in almost all experiments on these plants applying Mg has not increased yield.

An investigation was made of the effect of magnesium on the growth, the phosphorus absorption and translocation, and the cation content of soybean plants. The plants were grown in sand culture in the greenhouse, and the main treatment consisted of removing magnesium from the nutrient medium for various periods during the life cycle of the plants.

The removal of magnesium from the nutrient medium for any of seven different periods of 21 to 121 days during the life of soybean plants reduced growth, but its absence early in the life of the plant caused a greater reduction than its absence later in life.

The omission of magnesium from the nutrient solution did not retard phosphorus absorption but did have a significant effect on the movement and final location of phosphorus in the plants. The chemical composition of the parts of the mature plants revealed that the magnesium deficient plants contained a higher percentage of phosphorus in the vegetative organs and a lower proportion in the seeds than natural plants. A definite positive relationship existed between the magnesium and phosphorus content of the grain and a perfect negative correlation between the substance of these two elements in the leaflets. This finding offers support to the theory that magnesium may function as a carrier of phosphorus in plants.

The magnesium deficient plants absorbed slightly larger amounts of calcium and potassium on a percentage basis:

  1. R. Webb, A. J. Ohlrogge and S. A. Barber,1954. The effect of magnesium on the growth and the phosphorus content of soybean plants. Soil science society of America Journal, vol. 18 no. 4, p. 458-462

The effects of Mg deficiency on the photosynthesis and respiration of sugar beets (Beta vulgaris L. cv. F58-554H1) were studied by withholding Mg from the culture solution and by following changes in CO2 and water vapor exchange of attached leaves. Leaf blade Mg concentration decreased from about 1200 to less than 200 meq kg−1 dry matter without modification in the rate of photosynthetic CO2 uptake per unit leaf area, while from 200 to 50 meq kg−1 the rate decreased to one-third. Rates of photorespiratory evolution of CO2 into CO2-free air responded to Mg-like those of photosynthetic CO2 uptake, the rates dropping to one-half, below 200 meq kg−1. Respiratory CO2 growth in the dark increased almost 2-fold in low Mg leaves. Magnesium deficiency had less effect on leaf (mainly stomatal) diffusion resistance (r1) than on mesophyll resistance (rm); in Mg-deficient plants, rm increased from 2.9 to 7.1 sec cm−1, whereas r1 became significantly greater than the control value only in the most severe instances of Mg deficiency:

Norman Terry and Albert Ulrich, 1974.  Effects of magnesium deficiency on the photosynthesis and respiration of leaves of sugar beet. Plant Physiol. (3): 379–381.

Magnesium is required in significant amounts as it is needed everywhere inside and outside plant cells. Plants use magnesium to produce chlorophyll and seeds, regulate nutrient transport, and support carbohydrate metabolism and growth as a whole.  A shortage of magnesium results in low chlorophyll levels, slow growth, and poor bud development:

  1. Fluid Journal. 8(4): 12-13

Magnesium Sulfate

Fertilization of deficient trees with magnesium sulfate resulted in increased height growth over a period of at least three years. In two instances this increase was shown to be additive to that due to potassium, without evidence of significant interaction:

Earl L. Stone, 1952.  Magnesium deficiency of some northeastern pines, Soil Science Society of America Journal, vol. 17 no. 3, p. 297-300

Magnesium sulfate applied to the seedbed for potatoes increased yield in some but not all experiments on light soils, while in a few on both early and main crop potatoes it depressed yield.


Although magnesium (Mg) is one of essential nutrients, involved in many enzyme activities and the structural stabilization of tissues, its importance as a macronutrient ion has been overlooked in recent decades by botanists and agriculturists, who did not regard Mg deficiency (MGD) in plants as a severe health problem.

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