When soils are deficient in oxygen and have high proportion of salts or toxic substances the process of active absorption

Options

A. increases
B. remains unaffected
C. decreases
D. stops

Answer

### Step-by-Step Solution:

1. **Understand the Types of Absorption**:
- Plants utilize two main types of water absorption: **active absorption** and **passive absorption**. Active absorption requires energy (ATP) to move water against a concentration gradient, while passive absorption occurs through diffusion without energy expenditure.

**Hint**: Remember the difference between active and passive absorption in terms of energy usage.

2. **Identify the Conditions Affecting Absorption**:
- The question specifies conditions such as **deficient oxygen**, **high salt concentration**, and **toxic substances** in the soil. These conditions can significantly impact the absorption process.

**Hint**: Consider how each of these conditions might affect plant metabolism and water uptake.

3. **Impact of Low Oxygen on Respiration**:
- Low oxygen levels in the soil lead to reduced respiration rates in plant roots. Since respiration is crucial for energy production (ATP), a decrease in respiration will subsequently reduce the energy available for active absorption.

**Hint**: Think about how respiration is linked to energy production and how this affects absorption.

4. **Consequences of Reduced Respiration**:
- The reduction in respiration affects the metabolic activities of the cells, leading to a decreased rate of water absorption. This is because active absorption relies on metabolic energy.

**Hint**: Link the reduction in respiration directly to the decrease in active absorption.

5. **Effect of High Salt Concentration**:
- High concentrations of salts in the soil create a condition known as **physiological drought**, where the soil has water but the plant cannot absorb it effectively. This further decreases the rate of active absorption.

**Hint**: Consider how osmotic pressure changes with high salt concentrations and its effect on water movement.

6. **Toxic Substances and Carbon Dioxide Accumulation**:
- In low oxygen conditions, carbon dioxide can accumulate, which may have toxic effects on the plant. This toxicity can also inhibit water absorption.

**Hint**: Reflect on how toxic substances can disrupt normal physiological processes in plants.

7. **Conclusion**:
- Given the conditions of low oxygen, high salts, and toxic substances, the process of active absorption in plants will **decrease**.

**Final Answer**: The process of active absorption will decrease when soils are deficient in oxygen and have a high proportion of salts or toxic substances.