The plant growth regulators are small, simple molecules of diverse chemical composition. They are

Plant growth regulators (PGRs) are small, simple molecules with diverse chemical compositions that regulate plant growth and development at low concentrations [1]. These molecules are classified based on their chemical nature. Auxins, such as indole-3-acetic acid (IAA), are indole compounds. Cytokinins, like kinetin and zeatin, are adenine derivatives [1]. Gibberellins are classified as terpenes (specifically diterpenoids), while abscisic acid (ABA) is derived from carotenoids [1]. Ethylene, another major PGR, is a simple gaseous molecule [1]. Unlike primary metabolites like carbohydrates, fats, and proteins, these hormones act as signaling molecules to coordinate physiological processes such as cell division, elongation, and responses to environmental stimuli. Therefore, the diverse chemical groups representing PGRs include indole compounds, adenine derivatives, carotenoids, and terpenes.

Sources

1. [1] https://pmc.ncbi.nlm.nih.gov/articles/PMC516799/