Page 2 - LN-CH-12

2. Act as major constituents of macromolecules and co-enzymes.

Various forms and function of essential nutrients-

1. Nitrogen- required by plants in greatest amount, it is absorbed by plants as NO3,

NO2 and NH4", It is one of the major constituent of proteins, nucleic acids and

vitamins.

2. Phosphorus-Absorbed by plants from soil in the form of phosphate ions. It is the

constituent of cell membrane. All nucleic acids and nucleotides require phosphorus.

3. Potassium - absorbed as potassium ions (Kl. Help to maintain cation-anion balance in
cells. It is involved in protein synthesis, opening and closing of stomata.

4. Calcium - absorbed by plants from soil in form of Calcium ions (Ca2•). Used in

synthesis of cell wall. It activates certain enzymes.

5. Magnesium- absorbed by plants in form of Mg2• ions. It activates the enzymes for
respiration, photosynthesis, and involved in synthesis of DNA and RNA. It is

constituent of chlorophyll.

6. Sulphur- plants obtain sulphur in form of sulphate (Soi·). Present in amino acids

(cysteine, methionine) and is main constituent of coenzymes and vitamins.

7. Iron- obtained in the form of ferric iron (Fe3•). It is important constituent of

protein involved in transport system.

8. Manganese-absorbed in form of Mn2• ions. Main function is splitting of water to liberate

Hydrogen and Oxygen during photosynthesis.

9. Zinc-obtained as Zn2• ions. Activate enzymes like carboxylases. Needed in formation of

Auxin.
10. Copper -absorbed as cupric ions(Cu2). Involved in various metabolic activities and

redox reactions.

11. Boron-absorbed as B03- or BO4- ions. Required for uptake of calcium, cell elongation

and pollen germ.ination.

12. Chlorine - it is absorbed in form of Ch- ions. Determine the solute concentration

and splitting of water during photosynthesis.

Deficiency Symptoms of Essential elements

• When supply of essential elements becomes limited, plant growth is retarded. The

concentration of essential elements below which plant growth is retarded is

called critical concentration.