Which one of the following is present in chlorophyll which gives a green colour to plant leaves?

Chlorophyll is the primary pigment responsible for the green color of plant leaves [c3][t2]. Chemically, chlorophyll is a chelate consisting of a large organic porphyrin ring with a central metal ion [t1][t4]. This central atom is magnesium (Mg), which is coordinated to four nitrogen atoms in a square planar arrangement [t4][t5]. Magnesium is essential for the structural stability of the chlorophyll molecule and plays a critical role in photosynthesis by facilitating the transfer of electrons [t5]. While other elements like nitrogen are integral parts of the molecule [c1], magnesium specifically occupies the central position, similar to how iron sits at the center of heme in hemoglobin [t1]. A deficiency in magnesium leads to a shortage of chlorophyll, causing leaves to lose their green color [t7]. Therefore, magnesium is the specific element present in chlorophyll that enables its light-absorbing properties and green appearance [c1][t4].

Sources

1. [1] Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 25: Agriculture > Nitrogen (N) > p. 363
2. [2] Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 13: Plant Diversity of India > Leaves: > p. 204