Which of the following nutrients is not a structural component of the plant

Plant nutrients are categorized based on their physiological roles. Nitrogen (N) is a structural component of proteins, nucleic acids, and chlorophyll [1][t2]. Phosphorus (P) is a structural constituent of cell membranes (phospholipids), nucleotides (DNA/RNA), and ATP [t1][t2]. Calcium (Ca) serves a critical structural role in the cell wall (as calcium pectate) and cell membranes, providing rigidity and stability [t4][t6][t8]. In contrast, Potassium (K) is not a structural component of any plant molecule. Instead, it exists in ionic form within the cell sap, functioning primarily as an osmotic regulator, enzyme activator, and balancer of ionic charges [t1][t2][t4]. It is essential for the opening and closing of stomata and maintaining turgor pressure but does not form part of the plant's physical architecture [t4]. Therefore, potassium is the non-structural nutrient among the options.

Sources

1. [1] Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 25: Agriculture > Nitrogen (N) > p. 363