It is due to osmosis because of difference in concentration gradient between soil and roots

**Answer:**

The uptake of soil ions by the root system is a process of diffusion.

**Diffusion:**
Diffusion is the movement of particles or ions from an area of higher concentration to an area of lower concentration. It is a passive process that occurs due to the random motion of particles. Diffusion plays a crucial role in the uptake of soil ions by the root system.

**Process of Ion Uptake:**

1. **Root Hair Formation:** The root system of plants consists of root hairs, which are tiny extensions of the root epidermal cells. These root hairs increase the surface area of the roots, facilitating better absorption of water and nutrients.

2. **Concentration Gradient:** The soil contains a higher concentration of ions compared to the root cells. This concentration gradient acts as a driving force for the diffusion of ions into the root.

3. **Membrane Transporters:** The root cells possess specific membrane transporters, such as ion channels and carrier proteins, which facilitate the movement of ions across the cell membrane. These transporters allow the passage of ions based on their concentration gradients.

4. **Selective Ion Uptake:** Different ions have different transport mechanisms. For example, some ions may be taken up by facilitated diffusion through protein channels, while others may require active transport utilizing energy in the form of ATP. This selectivity ensures that only essential ions are taken up by the roots.

5. **Symplastic and Apoplastic Pathways:** The ions can enter the root cells through either the symplastic pathway (moving through the cytoplasm via plasmodesmata) or the apoplastic pathway (moving through the cell walls and intercellular spaces). Both pathways contribute to the overall uptake of ions by the root system.

6. **Root Pressure and Transpiration:** Once inside the root cells, the ions can be transported upwards through the xylem vessels with the help of root pressure and transpiration pull. Root pressure is the osmotic pressure generated by the active transport of ions into the xylem, while transpiration pull is the force exerted by the evaporation of water from the leaves.

In summary, the uptake of soil ions by the root system is a process of diffusion, where ions move from an area of higher concentration (soil) to an area of lower concentration (root cells) through selective ion channels and carrier proteins. This process is crucial for the absorption of essential nutrients by plants.