Moderate increase in the requirement of trace elements induces:

Options

A. Balancing effect
B. Osmotic effect
C. Toxic effect
D. Neutralising effect

Answer

To solve the question regarding the effects of a moderate increase in the requirement of trace elements, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Trace Elements**:
- Trace elements are essential micronutrients required by plants in very small quantities. They play a crucial role in various physiological and biochemical processes within the plant.

**Hint**: Remember that trace elements are different from macronutrients, which are needed in larger amounts.

2. **Critical Concentration**:
- Each trace element has a critical concentration range. If the concentration of a trace element falls below this range, it leads to deficiency symptoms, which can hinder plant growth and development.

**Hint**: Think about what happens when nutrients are insufficient; plants show signs of deficiency.

3. **Effects of Increased Concentration**:
- If the concentration of trace elements is increased moderately, it can lead to toxicity. This means that while trace elements are essential, too much of them can be harmful to the plant.

**Hint**: Consider the balance needed in nutrient concentrations; too much of a good thing can be bad.

4. **Conclusion**:
- Therefore, a moderate increase in the requirement of trace elements induces a toxic effect on plants. This is because the elements are needed within a narrow range, and exceeding this range can lead to adverse effects.

**Hint**: Recall that nutrient toxicity can manifest in various ways, affecting plant health and growth.

### Final Answer:
A moderate increase in the requirement of trace elements induces a **toxic effect**.