Plant growth regulators (PGRs), also known as phytohormones, are organic compounds other than nutrients which in small amounts promote, inhibit or otherwise modify any physiological process in plants. The main classes of PGRs include Auxins (indole compounds, e.g., IAA), Cytokinins (adenine derivatives, e.g., kinetin), Gibberellins (terpenes, e.g., GA3), Abscisic Acid (carotenoid derivatives/ terpenes, e.g., ABA), and Ethylene (a gaseous hormone). These chemical classifications align with the options provided.
The plant growth regulators are small, simple molecules of diverse chemical composition. They are
Asked in UPSC CDS 1 2017 · Topic: Plant Hormones (Auxins: Biosynthesis, Transport, and Physiological Effects)
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Answer: B. indole compounds, adenine derivatives, carotenoids and terpenes
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