Question

How are minerals absorbed by the plants?

Answer 1

Hint: In plants, mineral absorption is also called the mineral uptake. It is defined as the way in which the minerals enter the cellular material.

Complete Answer:
- Plants absorb minerals in the form of ions from the soil. Earlier it was thought that the absorption of minerals takes place in plants along with the absorption of water but later we get to know that both the processes are different.
- In order to absorb minerals, they should be dissolved in water. Plants absorb minerals through the roots. Larger the surface area of roots, more the minerals get absorbed.

There are two modes of mineral absorption:
1. Passive mineral absorption – It is a passive process and does not require the expenditure of energy. It occurs along the concentration gradient i.e. from a region of higher concentration to a region of lower concentration by simple diffusion.
2. Active mineral absorption – It is an active process and requires the expenditure of ATP (Adenosine triphosphate). It can occur both along and against the concentration gradient by simple osmosis or through special carrier proteins in the plasma membrane.

There are three main mechanisms of mineral absorption:
(I) Ion exchange – In this method the ions adsorbed on the surface of the root can exchange with the ions of the same charge from the soil solution. For example – Hydrogen ions adsorbed on the surface of root cells can be exchanged with potassium ions in the soil.

(II) Carrier concept – According to this theory, the plasma membrane is completely impermeable to some ions. The absorption of these ions is facilitated by some special proteins on the plasma membrane called carrier proteins. Here first the ions are combined with carrier protein to form a carrier – ion complex. The carrier-ion complex moves across the plasma membrane. When it reaches to the inner surface of the membrane, it releases the ions into the lumen of the cell. After this it will go back to accept new ions.

(III) Donnan equilibrium – According to this theory, there are some ions present inside the root cells which are called indiffusible ions or fixed ions. These ions do not diffuse outside through the plasma membrane. If a cell has cations as fixed ions, such a cell can absorb anions from the soil in order to maintain electrical potential balance. The absorption of anions causes Donnan equilibrium of anions and cations. By attaining equilibrium the root cells can absorb any mineral in their ionic form.

Note: Minerals are the elements that are necessary for the proper functioning of the body. They are defined as the naturally occurring inorganic nutrients found in the soil. For example – Manganese is a mineral which is required for the synthesis of Chlorophyll and necessary for photosynthesis during photolysis of water.