Mineral and Nutrition

Most of the minerals present in the soil can enter into plants through roots. More than 60 types of elements are found in different plants. The elements which are found in plants can be determined by the method, called Ash analysis.




Criteria of Essentiality

According to Arnon - the criteria for the essentiality of minerals are:-

  1. The element must be absolutely necessary for supporting normal growth and reproduction. In the absence of the element, the plants do not complete their life cycle or set the seeds.
  2. The requirement of the element must be specific and not replaceable by another element. In other words, the deficiency of any one element cannot be met by supplying some other element.
  3. The element must be directly involved in the metabolism of the plant. 


Methods To Study The Mineral Requirements of Plants


In 1860, Julius Von Sachs (a prominent German botanist) demonstrated for the first time, that plants could be grown to maturity in a defined nutrient solution in the complete absence of soil. The technique of growing plants in a nutrient solution without soil is called hydroponics. Hydroponics has been successfully employed as a technique for the commercial production of vegetables like tomato, seedless cucumber, and lettuce. By this method, essential elements were identified and their functions and deficiency symptoms were discovered.

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Essential Elements

  • About more than 60 types of elements are present in the plant body but only 17 elements are considered essential elements.
  • C, H, O, N, P, K, S, Ca, Mg, Fe, Cu, Zn, B, Cl, Mn, Mo, Ni
  • Except for these seventeen essential elements, there are some beneficial elements such as Na, Si, Se, Co.
  • Among 17 essential elements C, H & O are obtained from the air and soil in the form of CO2 & H2O, not in the form of ions, so these are called non-mineral nutrients or elements. Others are mineral nutrients.


Classification of Essential Elements

A. based on the quantity or requirements of the plants, essential elements can be classified into two groups:

  • Major elements/Macronutrients :
  1. Concentration must be excess of 10 mmole kg-1 of dry matter. C, H, O, N, P, K, S, Ca, Mg, 
  • Minor elements/Micronutrients :
  1. The concentration required less than 10 m moles kg-1of dry matter. 
Fe, Cu, Zn, B, Cl, Mn, Mo, Ni 


B. based on functions, essential elements can be grouped into four broad categories:

  • Essential elements as components of biomolecules and hence structural elements of cells (e.g., C, H, O, and N)
  • Essential elements that are components of energy-related chemical compounds in plants (e.g., Mg in chlorophyll and phosphorus in ATP).
  • Essential elements that activate or inhibit enzymes. (e.g., Mg, Zn, Mo, etc.)
  1. Mg2+ is an activator for both RuBisCO and PEPCase, both of which are critical enzymes in photosynthetic carbon fixation;
  2. Zn2+ is an activator of alcohol dehydrogenase and Mo of nitrogenase during nitrogen metabolism.
  • Some essential elements can alter the osmotic potential of a cell. (e.g., K, Cl, etc.)  


Deficiency Symptoms Of Essential Elements


Whenever the supply of an essential element becomes limited, plant growth is retarded.The concentration of the essential element below which plant growth is retarded is termed as critical concentration. The element is said to be deficient when present below the critical concentration.

Deficiency Symptoms of Essential Elements 

The kind of deficiency symptoms shown in plants includes chlorosis, necrosis, stunted plant growth, premature fall of leaves and buds, and inhibition of cell division.

  • Chlorosis:- The loss of chlorophyll leading to yellowing in leaves. This symptom is caused by the deficiency of elements N, K, Mg, S, Fe, Mn, Zn, and Mo.


  • Necrosis:- The death of tissue, particularly leaf tissue, is due to the deficiency of Ca, Mg, Cu, K.




  • Inhibition of Cell Division:- Lack or low level of N, K, S, Mo 
  • Delay In Flowering:- Lack or low level of N, S, Mo.


Mobility of Minerals


  • Actively mobilized within the plants and exported to young developing tissues, the deficiency symptoms tend to appear first in the older tissues.  
  • For example, the deficiency symptoms of nitrogen, potassium, magnesium, and phosphorus are visible first in the senescent leaves. 
  • The deficiency symptoms tend to appear first in the young tissues whenever the elements are relatively immobile and are not transported out of the mature organs, for example, elements like sulfur and calcium are a part of the structural component of the cell, and hence are not easily released.



Deficiency Symptoms Of Essential Elements

You can see from the above that the deficiency of any element can cause multiple symptoms and that the same symptoms may be caused by the deficiency of one of several different elements. Hence, to identify the deficient element, one has to study all the symptoms developed in all the various parts of the plant and compare them with the available standard tables. We must also be aware that different plants also respond differently to the deficiency of the same element.


Toxicity of Micronutrients 


  1. Any mineral ion (Micronutrient) concentration in plant tissue that reduces the dry weight of tissues by about 10 percent is considered toxic and this effect is called toxicity
  2. Ex: Excess of Mn (Manganese) cause appearance of brown spots surrounded by chlorotic veins (prominent symptom)
  3. Mn competes with iron (Fe) and magnesium (Mg) for uptake and with Mg for binding with enzymes.
  4. Mn also inhibits calcium translocation into the shoot apex.
  5. So the excess of Mn may, in fact, induce deficiencies of Fe, Mg, and Ca.
  6. Thus, what appears as symptoms of manganese toxicity may actually be the deficiency symptoms of Fe, Mg & Ca.






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