Premature death of plants is caused by the deficiency of:

Explanation

The correct answer is Magnesium. Magnesium is a critical component of chlorophyll, and its deficiency leads to chlorosis-a condition where leaves turn yellow due to insufficient chlorophyll production. This can severely affect photosynthesis, leading to premature death in plants if not corrected. While iron deficiency also causes chlorosis, it does not usually lead to premature death unless it is severe and prolonged. Phosphorus and potassium deficiencies impact other aspects of plant growth and health, but they do not directly lead to premature death.