NEET 2025 Zoology Question 173 Solution

Analyzing the correct plant developmental principles:

• • Statement A: Auxins (e.g. IAA, IBA, NAA) applied to unpollinated pistils stimulate pericarp enlargement without fertilization, producing seedless fruits (parthenocarpy), commercially exploited in tomatoes and watermelons. Statement A is CORRECT.
• • Statement B: Plant growth regulators encompass two broad functional categories: plant growth promoters (participating in cell division, elongation, flowering, fruiting) and plant growth inhibitors (mediating dormancy, abscission, and stress responses). Statement B is CORRECT.
• • Statement C: In plant development, differentiated parenchyma cells lose their specialization and regain mitotic activity (dedifferentiation) to form secondary meristems (interfascicular cambium, cork cambium). The progeny of these meristems subsequently lose division ability and re-specialize into permanent secondary vascular tissues (redifferentiation). Thus, dedifferentiation is a mandatory developmental prerequisite for redifferentiation. Statement C is CORRECT.

Identifying false claims:

• • Statement D claims "Abscisic acid is a plant growth promoter". NCERT explicitly classifies ABA as a general plant growth inhibitor, functioning as an antagonist to gibberellins and promoting seed dormancy and stomatal closure. Hence, Statement D is FALSE.
• • Statement E claims "Apical dominance promotes the growth of lateral buds". In apical dominance, growing apical buds synthesize auxin which suppresses and inhibits the growth of axillary/lateral buds. Removal of the shoot tip (decapitation) relieves this inhibition and allows lateral branches to grow (practiced in tea plantations and hedge-making). Hence, Statement E is FALSE.

Only statements A, B, and C are correct, which corresponds to Option (1).