The correct Answer is A-4, B-3, C-2, D-1
Explanation
Plant growth regulators (PGRs) are small, simple molecules of diverse chemical composition that regulate plant growth and development. They are broadly classified into growth promoters (auxins, gibberellins, cytokinins) and growth inhibitors (abscisic acid, ethylene).
Statement-wise Analysis
- A. Indole-3-acetic acid (IAA) - 4. Indole compound
- Correct: Indole-3-acetic acid (IAA) is a naturally occurring auxin. Auxins are generally indole derivatives.
- B. Kinetin - 3. Adenine derivative
- Correct: Kinetin is a modified form of adenine, a purine. It is a type of cytokinin, which are adenine derivatives.
- C. Abscisic acid (ABA) - 2. Carotenoid derivative
- Correct: Abscisic acid (ABA) is synthesized from mevalonic acid pathway intermediates, which are also precursors for carotenoids. Thus, ABA is a carotenoid derivative.
- D. Ethylene - 1. Gaseous hormone
- Correct: Ethylene is a simple gaseous plant growth regulator. It is the only gaseous hormone among the major PGRs.
Key Takeaway
Plant growth regulators have distinct chemical natures, such as indole compounds (auxins), adenine derivatives (cytokinins), carotenoid derivatives (abscisic acid), and gaseous hydrocarbons (ethylene), which determine their classification and function.