Essential Mineral Elements – Class 12 | Chapter – 12 | Biology Short Notes Series PDF

Essential Mineral Elements: Plants absorb water, minerals, and other nutrients from the soil which is carried to the other parts of the plant by plant tissues (mostly xylem). Abundant minerals are present in the soil that are absorbed by the roots of the plants and transferred to the other parts of the plant. This is the way, all other living beings like humans and animals receive nutrients when we consume different parts of the plant. Essential mineral elements are a mix of macronutrients like calcium, phosphorus, sodium, carbon, etc. and micronutrients like iron, manganese, zinc, copper, etc. that are necessary for the growth of plants and animals.

The Criteria to Determine Essential Minerals to the Plant are as follows-

  • Minerals absorbed from soil by roots of plants are mineral ions dissolved in soil medium. They support plant life through their entire life cycle and also for the production of seeds.

  • A few minerals like magnesium and phosphorus are crucial for the growth, development, and reproduction of plants.

  • Mineral deficiency like deficiency of nitrogen, iron, copper, sulfur leads to various problems like stunted growth, poor development, insufficient chlorophyll in leaves, cell senescence, etc. in plants.

  • Mineral potassium greatly influences the quality of fruits and vegetables.

  • Proper metabolism in plants is dependent on minerals like potassium, sodium, magnesium, and other elements.

Essential Mineral Elements

Based upon the above criteria only a few elements have been found to be absolutely essential for plant growth and metabolism. These elements are further divided into two broad categories based on their quantitative requirements.
(i) Macronutrients, and
(ii) Micronutrients

Macronutrients are generally present in plant tissues in large amounts (in excess of 10 mmole Kg –1 of dry matter). The macronutrients include carbon, hydrogen, oxygen, nitrogen, phosphorous, sulphur, potassium, calcium and magnesium. Of these, carbon, hydrogen and oxygen are mainly obtained from CO2 and H2O, while the others are absorbed from the soil as mineral nutrition.

Micronutrients or trace elements, are needed in very small amounts (less than 10 mmole Kg –1 of dry matter). These include iron, manganese, copper, molybdenum, zinc, boron, chlorine and nickel.

Essential elements can also be grouped into four broad categories on the basis of their diverse functions. These categories are:

(i) Essential elements as components of biomolecules and hence structural elements of cells (e.g., carbon, hydrogen, oxygen and nitrogen).

(ii) Essential elements that are components of energy-related chemical compounds in plants (e.g., magnesium in chlorophyll and phosphorous in ATP).

(iii) Essential elements that activate or inhibit enzymes, for example Mg2+ is an activator for both ribulose bisphosphate carboxylaseoxygenase and phosphoenol pyruvate carboxylase, both of which are critical enzymes in photosynthetic carbon fixation; Zn2+ is an activator of alcohol dehydrogenase and Mo of nitrogenase during
nitrogen metabolism. 

(iv) Some essential elements can alter the osmotic potential of a cell. Potassium plays an important role in the opening and closing of stomata. You may recall the role of minerals as solutes in determining the water potential of a cell.

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By Team Learning Mantras