The term "overdose" in the context of essential elements for plants suggests an excess or imbalance of nutrients, which can have negative effects on plant health. Among the options given:

(A) Nitrogen

Explanation: While all nutrients are essential for plant growth, an overdose or excessive application of nitrogen (option A) can lead to problems such as nutrient imbalance, environmental pollution, and increased susceptibility to certain diseases. Excessive nitrogen can cause rapid vegetative growth, but it may negatively impact other aspects of plant health, such as root development, flowering, and overall resilience.

Balanced nutrient management is crucial for optimal plant growth, and it's important to consider the specific requirements of each plant species and the soil conditions to avoid nutrient imbalances and potential negative effects on plant health.