Supply of excess fertilizer and watering of a grass lawn causes browning of grass leaves due to

Options

A. Decreased photosynthesis
B. Water-logging of soil
C. Leaching of fertilizer to lower soil strata
D. Osmosis and death of root .

Answer

**Step-by-Step Solution:**

1. **Understanding the Problem**: The question asks why excess fertilizer and watering lead to browning of grass leaves. It is important to analyze the effects of both excess fertilizer and water on the grass lawn.

2. **Excess Fertilizer Effects**: When too much fertilizer is applied, the concentration of solutes (fertilizers) in the soil solution increases significantly. This creates a high concentration of solutes in the soil compared to the concentration of solutes inside the plant roots.

3. **Osmosis Process**: Osmosis is the movement of water across a semi-permeable membrane from an area of lower solute concentration to an area of higher solute concentration. In this case, due to the high concentration of solutes in the soil (from excess fertilizer), water moves out of the plant roots into the soil.

4. **Exosmosis**: As a result of this osmotic pressure, the roots of the grass begin to lose water (exosmosis) instead of absorbing it. This loss of water leads to dehydration of the root cells.

5. **Death of Root Cells**: The dehydration of root cells can lead to their death. When the roots die, they are unable to absorb water and nutrients effectively.

6. **Impact on Leaves**: Since the roots are responsible for transporting water to the leaves, the death of root cells means that water cannot reach the leaves. This lack of water leads to browning of the grass leaves.

7. **Conclusion**: Therefore, the browning of grass leaves is primarily due to the process of osmosis leading to the death of root cells, which in turn prevents water from reaching the leaves.

**Final Answer**: The browning of grass leaves due to excess fertilizer and watering is caused by osmosis and death of root cells.

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