MINERAL NUTRITION

POINTS TO REMEMBER :

  • Autotrophs : An organism that synthesize its required nutrients from simple and inorganic substances.
  • Heterotrophs : An organism that cannot synthesize its own nutrients and depend on others.

Essential Mineral elements :

  • More than sixty elements found in different plants.
  • Some plant accumulates selenium, some other gold.

Criteria for Essentiality :

  • Element absolutely necessary for normal growth and reproduction.
  • In the absence of the element the plant can not complete their life cycle.
  • Role of the element can not be replaced by any other elements.
  • The element must be directly involved in the metabolism of plant.

Macronutrients : are generally present in the plants tissues in large amount (in excess of 10 mmole
Kg-1 of dry matter).
Micronutrients : or trace elements are needed in very small amounts (less than 10 mmole Kg-1 of dry matter)

Four group of essential elements :

  • As components of biomolecules and forms structural elements of cells (e.g. carbon, hydrogen, oxygen and nitrogen)
  • As components of energy-related chemical compounds in plants. (magnesium in chlorophyll and phosphorous in ATP)
  • Element that activate or inhibit enzymes  (Mg2+, Zn2+)
  • Alter the osmotic potential of a cell. (K+)

Role of macro and micro-nutrients :

Nitrogen :

  • Absorbed in the form of NO2- or NH4+
  • Required by meristematic tissue and metabolically active tissue.
  • Constituent of proteins, nucleic acids, vitamins and hormones.

Phosphorus :

  • Absorbed in the form of H2PO4- or HPO42-.
  • Constituents of cell membrane certain proteins, all nucleic acids and required in phosphorylation reaction.

Potassium :

  • Absorbed as potassium ion (K+)
  • Required in meristematic tissues.
  • Maintain cation and anion balance in cell.
  • Opening and closing of stomata.
  • Activation of enzyme.
  • Maintenance of turgidity of cells.

Calcium :

  • Absorbed in the form of calcium ions (Ca2+).
  • Required by meristematic and differentiating tissues.
  • Used in synthesis of cell wall particularly as calcium pectate in middle lamella.
  • Required during formation of mitotic spindle.
  • Involved in normal functioning of cell membrane.
  • Activate certain enzyme.
  • Important role in regulating metabolic activity.

 

CBSE Biology (Chapter Wise) Class XI ( By Mr. Hare Krushna Giri ) 
Email Id : [email protected]