Chlorosis in plants is caused by the deficiency of:

Explanation

Chlorosis is the yellowing of leaves due to a lack of chlorophyll, often caused by nutrient deficiencies. Nitrogen is a vital component of chlorophyll, and magnesium is part of the chlorophyll molecule. Therefore, deficiencies in nitrogen and magnesium can both result in chlorosis. Potassium, while important for various plant functions, does not directly affect chlorophyll production, so its deficiency does not typically cause chlorosis.