Depending on the requirements, plant nutrients are classified as micronutrients and macronutrients. Which one of the following is an example of a macronutrient?

Plant nutrients are categorized into macronutrients and micronutrients based on the quantity required for growth. Macronutrients are essential elements needed in relatively large amounts, typically found in plant tissues at concentrations of 1000 ppm or greater. These are further divided into primary macronutrients (Nitrogen, Phosphorus, Potassium) and secondary macronutrients (Calcium, Magnesium, and Sulfur) [2]. Magnesium is a critical secondary macronutrient essential for photosynthesis and the synthesis of chlorophyll. In contrast, micronutrients like Manganese, Copper, and Chlorine are required in much smaller quantities (less than 100 ppm) and often function as enzyme activators [2]. Therefore, among the given options, Magnesium is the only macronutrient, while Manganese, Copper, and Chlorine are classified as micronutrients [2].

Sources

1. [2] Indian Economy, Nitin Singhania .(ed 2nd 2021-22) > Chapter 9: Agriculture > FERTILISERS > p. 302
2. [1] Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 25: Agriculture > z. Micronutrientsl > p. 363