Which one of the following elements is essential for the formation of chlorophyll in green plants?

Magnesium (Mg) is an essential element for the formation of chlorophyll in green plants. It serves as the central metal ion in the chlorophyll molecule, specifically embedded within a porphyrin or chlorin ring structure [1]. This central coordination site is critical for the pigment's light-absorption and photochemical functions, allowing plants to capture solar energy for photosynthesis. Magnesium also acts as an activator for various enzymes involved in plant metabolism [1]. A deficiency in magnesium leads to interveinal chlorosis, where leaves turn yellow because the plant cannot synthesize sufficient chlorophyll. While other elements like nitrogen are also integral parts of the chlorophyll molecule, magnesium is the specific metallic element that occupies the central position necessary for its structural integrity and biological activity [2].

Sources

1. [1] Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 25: Agriculture > Nitrogen (N) > p. 363
2. [2] https://www.nature.com/articles/s41598-017-07305-6