Monday, August 31, 2020

Mineral Nutrition - Notes | Class 11 | Part 2: Mechanism of Absorption of Elements

12. MINERAL NUTRITION 

MECHANISM OF ABSORPTION OF ELEMENTS

The inward movement of ions into the cells is called influx and the outward movement is efflux.

The process of absorption includes 2 main phases:
  • First phase: Initial rapid and passive uptake of ions into the apoplast (free space or outer space) of cells. It usually occurs through ion-channels (trans-membrane proteins that function as selective pores).
  • Second phase: The ions are taken in slowly into the symplast (inner space or cytoplasm) of the cells. It is an active process (requires energy).

Translocation of solutes


Mineral salts are translocated through xylem along with the ascending stream of water.

Analysis of xylem sap shows the presence of mineral salts in it. Use of radioisotopes of mineral elements also proved that they are transported through the xylem.
   

Soil as Reservoir of Essential Elements


Weathering and breakdown of rocks enrich the soil with dissolved ions and inorganic salts.

Roles of soil:
  • It supplies minerals and holds water.
  • It harbours nitrogen-fixing bacteria and other microbes.
  • It supplies air to the roots.
  • It acts as a matrix that stabilizes the plant.
Deficiency of essential minerals affects the crop-yield. So fertilisers should be supplied. Both macro-nutrients and micro-nutrients form components of fertilisers.
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