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Biology Question 110 – NEET-UG 2026

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Which of the following plant growth regulators is used as herbicide ?

Plant growth regulators (PGRs) are small, simple molecules of diverse chemical composition, which regulate plant growth and development.

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Ninja Strategy•Function-Based Elimination

Quickly recall the primary functions of each plant growth regulator to identify the one known for herbicidal action.

Step 1: Identify Plant Growth Regulators (PGRs) and their functions✦ Active

Plant growth regulators are chemical substances that influence the growth and differentiation of plant cells, tissues, and organs. They are broadly classified into plant growth promoters (auxins, gibberellins, cytokinins) and plant growth inhibitors (abscisic acid, ethylene).

Step 2: Recall the specific uses of common PGRs○ Expand

Auxins (like 2,4-D) are known for promoting cell elongation, root initiation, and also for their herbicidal properties at higher concentrations. Kinetin (a cytokinin) promotes cell division. Abscisic acid (ABA) promotes dormancy and abscission. Gibberellins promote stem elongation and seed germination.

💡 Teacher's Secret Hint

Remember that the effect of a PGR can be concentration-dependent, especially for auxins.

Step 3: Determine which PGR acts as a herbicide○ Expand

Among the given options, 2,4-D (2,4-Dichlorophenoxyacetic acid) is a synthetic auxin widely used as a selective herbicide to kill dicotyledonous weeds without affecting monocotyledonous crop plants.

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