QS Study

Plants can only absorb soluble minerals. They absorb minerals dissolved in solution from the soil through their root hair cells. Organs through which plants absorb mineral salt:

  • Plants absorb mineral salt through the newly formed cells of the growth region of the root.
  • Some salt is also absorbed by root hairs.

The nature of the salt:

Plants cannot absorb mineral salt directly. Salts are usually absorbed as ions. The mineral salts of the soil being dissolved in water are divided in to canons (+) and anions (-) and plants absorb than in this condition.

The method of salt absorption:  The method of salt absorption is mainly of two types-

  1. Passive absorption
  2. Active absorption

Passive absorption: Metabolic energy is not required in this process.

Active absorption: Metabolic energy is required in this process.

Passive absorption occurs by the following ways:

  • Diffusion method: When the ion concentration of mineral salts of the plant cells becomes higher than the ion concentration of the same mineral salts present in the solution of the soil, the ion of the solution of the soil enters the cell sap through diffusion.
  • Ion exchange method: H+ ion from the cell sap of the root is released to the solution present outside of the root. Now, K+ ion enters the cell from the solution outside of the cells in order to make the cells electrically neutral Now. Cl ion enters the cell sap, in the same way, due to the exchange of ions in between OH+ and Cl.
  • Donnan equilibrium method: In order to make the indiffusable fixed negativity charged ions, if there is any in the cells, some positively charged ions enter the cells from outside of the cells.

Active absorption: It is seen from the active absorption that the ions enter the cells if the concentration of ions present in the cells is less than the concentration of ions outside of the cells. They are in close contact with the thin film of water surrounding the soil particles. Metabolic energy is required in this case.