How the minerals are absorbed by the plants? Find out.

This article explores the process by which plants absorb minerals and the various mechanisms involved.

For the longest time, it was thought and perceived that roots absorb water and minerals from the soil the same way, but recent studies have changed this, and a new theory regarding how are the minerals absorbed by the plants has been established. A new study done in detail established that water and minerals are absorbed by plants in different modes. While absorption of water by roots is done from the soil, minerals are absorbed from the soil solution through ions. They absorb the mineral mainly through the meristematic regions of the roots.

​There can also be different locations through which minerals can be absorbed, either on the root surface or the entire root, including root hairs, but that depends on the availability of the minerals and tissue demands. However, when speaking directly, minerals in plants are absorbed during both passive and active methods and are further divided into three mechanisms. Let’s dive into the details about how plants absorb minerals:

​Passive and Active Methods of Mineral Absorption in Plants

​Before diving into the three main mechanisms of mineral absorption, let us first understand the passive and active methods of mineral absorption in plants:

​Passive Absorption

​In the passive absorption method, there is no need for metabolic energy expenditure, and it naturally occurs along the concentration gradient by simple diffusion. Below are some of the factors that determine the passive absorption of minerals in plants:​

• It doesn’t require energy.

• It is a spontaneous process.

• It doesn’t cause salt accumulation in the cells.

• The rate of mineral absorption is not dependent on respiration.

• It doesn’t require any particular carrier molecules.

• It has less efficiency of absorption.

• Mineral ions proceed towards the equilibrium constant.

Active Absorption​

For active mineral absorption, there is a need to expend metabolic energy, which can occur along and against the concentration gradient through osmosis or a protein carrier present in the plasma membrane. Below are some factors that determine the process of active absorption:

• It is a chemical but non-spontaneous process.

• It requires energy to occur.

• It causes salt accumulation.

• It needs a specific carrier protein.

• The rate of mineral absorption is dependent on respiration.

• It has a high efficiency of absorption.

Mechanisms of Mineral Absorption in Plants

​Now that you have understood about passive and active mineral absorption, let us move on to understanding the main mechanisms of absorption, which are mainly divided into three processes:

​Ion Exchange

​In the process of Ion exchange for mineral absorption in plants, the ions that are absorbed on the surface of the roots can exchange with the ions of the same charge present in the soil solution. To understand it better, the H⁺ ions absorbed by the surface of the root can be exchanged with K⁺ ions present in the soil. This absorption is explained further in two different theories that we are discussing here:​

Contact Exchange Theory

​Based on the contact exchange theory, the ions absorbed on the surface of the root cells or clay particles move in continuous oscillation. However, when the root and the clay particles are close to each other, the oscillation radius of ions present in the clay particles can overlap with the ions present in the root cells. When this overlapping happens, there is a possibility of the spontaneous exchange between the ions present in the root surface and clay particles.​

Carbonic Acid Exchange Theory

​In this theory, the soil solution comes into play and acts as a medium of ion exchange. The CO2 released during the respiration of the root cells mixes with the water to form (H2CO3).

​After the carbonic acid comes into being, it immediately dissociates into H+ and HCO3 in the soil solution, and H+ ions further exchange with the cations absorbed by the clay particles, and the cations from micelles are released into the soil solution, which is absorbed by the root cells.

​The Carrier Concept

​This concept was put forward by Van Den Honert in 1937, and based on this theory, the plasma membrane of the plants is impermeable to certain ions. The absorption of these ions is regulated by specific proteins on the plasma membrane and is called “Carrier Proteins.”

​At first, these carrier proteins are combined with the ions and form a carrier-ion complex, and then reach the inner surface of the membrane. After they reach the membrane, they release the ions in the lumen of the cell, and the carrier proteins go back to the outer surface to accept new ions.

​Donnan Equilibrium

The Donnan Equilibrium theory is about the accumulation of some mineral ions inside the cell against the concentration gradient without the expenditure of metabolic energy.  Based on this theory, some ions present inside the root cell are called fixed ions or indiffusable ions because of their inability to diffuse outside through the plasma membrane. However, there must be a balance by absorbing ions of the opposite charge.

​If fixed anions are present inside the membrane, as a result, more cations will be absorbed to maintain the electrical equilibrium. This will make the cation concentration higher inside than outside the solution. This phenomenon of balancing the ions is called the Donnan equilibrium.

​Final Words

​The absorption of minerals is quite a complex task, but this guide will help you understand the process in an easier way. If you have been believing in the earlier theory of mineral absorption being done in plants the same way the water is absorbed, this guide will clear your doubts, and you will actually come to understand the right ways how are minerals absorbed by the plants.

​FAQs

How are the minerals absorbed by the plants?

The absorption of minerals by plants is done in various ways, but in simple terms, it is absorbed from the soil solution through the meristematic regions of the roots.

​Where are minerals absorbed from in plants?

The minerals are absorbed in the plants in the root system, precisely in the root hair that goes into the soil.

​How do plants absorb nutrients from soil?

Plants absorb nutrients from the soil through their roots and take up the dissolved minerals via mass flow, root interception, and diffusion.​

What are the main minerals?

The main minerals needed by plants include Nitrogen, Potassium, Calcium, Phosphorus, Sulfur, Magnesium, along with Carbon, Oxygen, and Hydrogen.

​What is the process by which minerals are absorbed from the soil?

The process through which minerals are absorbed from soil is done in two ways, active and passive, which are further divided into three mechanisms, including Ion Exchange, the Carrier Concept, and Donnan Equilibrium.

What is the mechanism of mineral absorption in plants?

There are 3 mechanisms through which mineral absorption is done in plants, which are  Ion Exchange, the Carrier Concept, and Donnan Equilibrium.

​How do plants absorb mineral ions?

Plants absorb mineral ions through their roots from the soil solution in active and passive modes.