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NEET Biology Mineral Nutrition

Mineral Nutrition PDF Notes, Important Questions and Synopsis

 

SYNOPSIS

  • Absorption, distribution and metabolism of various mineral elements by plants is called mineral nutrition.
  • Methods to Study the Mineral Requirement of Plants
    • Hydroponics: Technique of growing plants in a nutrient solution.
    • Aeroponics: Technique of growing plants without a growing medium.
    • Sand Culture: Sand is used as rooting medium and nutrient solution is added to it.

  • Physiological Role and Deficiency Symptoms of Macronutrients and Micronutrients


    Macronutrients are used in relatively large amounts by plants for their growth.

    Macroelement

    Physiological Role

    Deficiency Symptoms

    Nitrogen

     

    • Absorbed mainly as NO3, NO2, NH4+.
    • Chief constituent of proteins, nucleic acids, amino acids, purines.
    •  Yellowing of leaves and development of chlorosis.

    Sulphur

    • Absorbed in the form of SO42− ions.
    • Determines protein structure.
    • Young leaves become chlorotic, anthocyanin pigmentation.

    Phosphorus

    • Absorbed in the form of H2PO4 or HPO42− ions.
    • Acts as an activator of some enzymes.
    •  Disruption of general metabolism.
    • Abnormalities in the shape and size of chloroplasts.

    Calcium

    • Absorbed in the form of Ca2+ ions.
    • Essential for chromatin or mitotic spindle organisation.
    •  Margins of younger leaves show chlorosis.

    Potassium

      • Absorbed as K+ ions.
      • Regulates stomatal movement.
    •  Weak stalks are developed.

    Magnesium

    • Absorbed in the form of Mg2+ ions.
    • Helps in photosynthesis.
    •  Yellowing of leaves.
    • Tips and margins of leaves turn upwards.

    Micronutrients are required by plants in minute quantities.

    Microelement

    Physiological Role

    Deficiency Symptoms

    Iron

    • Absorbed in the form of Fe3+ ions.
    • Plays an important role in electron transport systems.
     
    • Development of characteristic chlorotic spots and the veins remain green.

    Boron

    • Absorbed as BO33− or B4O72−.
    • Regulates carbohydrate metabolism.

     

    • Deformation, discolouration and disorganisation of meristematic tissue.

    Manganese

    • Absorbed in the form of Mn2+ ions.
    • Plays a role in photo-oxidation of H2O and release of molecular O2.
    •  Chlorosis and necrosis in the interveins of leaves.

    Copper

    • Absorbed in the form of Cu2+ ions.
    • Plays a key role in the electron transport chain in photosynthesis.
    • Distortion and chlorosis in leaves followed by necrosis of the tips of young leaves.

    Zinc

    • Absorbed in the form of Zn2+ ions.
    • Plays an important role in the synthesis of auxins.
    •  Shortening of internodes resulting in stunted plant growth.
    • Suppression of seed formation.

    Microelement

    Physiological Role

    Deficiency Symptoms

    Molybdenum

    • Absorbed in the form of MoO22+ ions.
    • Required for nodulation in legumes, synthesis of tannins and reduction of nitrates to nitrites.
    • Development of chlorosis along with poor leaf growth.
    • Reduction in nitrogen fixation in symbiotic plants.

    Chlorine

    • Absorbed in the form of Cl anions.
    • Essential in the transport of electrons from water to photo oxidised chlorophyll.
    • Wilted leaves, which then become chlorotic and necrotic.

    Nickel

    • Catalyses the hydrolysis of urea to CO2 and NH4.
    •  Development of necrotic spots at the tips.

 

  • The process of conversion of free nitrogen (N2) to ammonia (NH3) to make it available for uptake by plants is called nitrogen fixation.
  • Rhizobium fixes atmospheric nitrogen in symbiotic association with the roots of leguminous plants.
  • Nodules act as sites for nitrogen fixation because they contain the enzyme nitrogenase and pigment leghaemoglobin essential for fixing atmospheric nitrogen.
  • Nitrogenase is a Mo–Fe protein which catalyses the conversion of atmospheric N2 to NH3.


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  • At physiological pH, ammonia is protonated to form ammonium (NH4+) ions.
  • In legumes, ammonia is assimilated into amino acids, amides or ureides.