Question

Short note on mineral nutrition

Answer 1

Macronutrients (Macroelements or major elements): Nutrients which are required by plants in larger amounts (Generally present in the plant tissues in concentrations of 1 to 10 mg per gram of dry matter).

(2) The macronutrients include carbon, hydrogen, oxygen, nitrogen, phosphorous, sulphur, potassium, calcium, magnesium.

(3) Micronutrients (Microelements or minor elements or trace elements): Nutrients which are required by plants in very small amounts, i.e., in traces (equal to or less than 0.1 mg per gram dry matter).

(4) The micronutrients include iron, manganese, copper, molybdenum, zinc, boron and chlorine. Recent research has shown that some elements, such as cobalt, vanadium and nickel, may be essential for certain plants.

(5) The usual concentration of essential elements in higher plants according to D.W. Rains (1976) based on the data of Stout are as follows:

Element

% of dry weight

                  Carbon

45

                  Oxygen

45

                  Hydrogen

  6

                  Nitrogen

1.5

                  Potassium

1.0

                  Calcium

0.5

                  Magnesium

0.2

                  Phosphorus

0.2

                  Sulphur

0.1

                  Chlorine

0.01

                  Iron

0.01

                  Manganese

0.005

                  Boron

0.002

                  Zinc

0.002

                  Copper

0.0001

                  Molybdenum

0.0001

Answer 2

All organisms consist of atoms of chemical elements. The final reservoirs of these elements on earth are the rocks, soil, the oceans and the atmosphere.

Only the green plants and certain microorganisms can primarily extract simple inorganic compounds and ions from the environment without being dependent on other living orgnisms. For this reason these organisms are called autotrophic or self-feeding. All inorganic plant requirements except carbon, hydrogen and oxygen, are obtained directly or indirectly from soil.

In 1804, de Saussure demonstrated that the inorganic elements contained in plant ash are obtained from the soil via the root system. These elements are essential to the growth and development of the plant.

As the sources of these inorganic requirements are minerals, the elements are known as mineral nutrients and the nutrition is called mineral nutrition. Scientific approach to determine the mineral content in plants started by Sachs and Knops in 1830 by culture of plants in acqueous nutrient solution, they prepared a list of elements essential to plant life.