Auxins as Herbicides: 2,4-D Selectivity — NEET Biology
✅ Asked in NEET 2024Auxin is used by gardeners to prepare weed-free lawns. But no damage is caused to grass as auxin (NEET 2024)
Auxin is used by gardeners to prepare weed-free lawns. But no damage is caused to grass as auxin (NEET 2024)
The plant hormone used to destroy weeds in a field is: (NEET 2021)
Answer & NCERT explanation
Correct answer: C — does not affect mature monocotyledonous plants.
Auxin DOES NOT AFFECT MATURE MONOCOTYLEDONOUS PLANTS. According to NCERT, mature monocots like grass are insensitive to auxin, while dicot weeds are sensitive and get killed by excessive auxin application. This selectivity makes 2,4-D effective as herbicide. Young monocots may respond, but mature ones are resistant, protecting established grass lawns.
Read more NCERT concept on the PYQ
Auxins also induce parthenocarpy, e.g., in tomatoes. They are widely used as herbicides. 2, 4-D, widely used to kill dicotyledonous weeds, does not affect mature monocotyledonous plants. It is used to prepare weed-free lawns by gardeners. Auxin also controls xylem differentiation and helps in cell division.
NTA tests whether students understand that 2,4-D is a selective herbicide that kills dicots but NOT mature monocots—this selectivity is the key concept. Students commonly mistake this by thinking 2,4-D kills all plants equally or confuse which plant type it affects. The trap: they may memorize "2,4-D kills weeds" without remembering the critical word "dicotyledonous." To get it right, remember that monocots (grasses) have different auxin sensitivity and developmental patterns, making them resistant to 2,4-D at maturity. This selectivity is why 2,4-D creates weed-free lawns—it removes dicot weeds while preserving monocot grass.
What does NCERT say about Auxins also induce parthenocarpy?
Has this concept appeared in NEET?
Which chapter is this from?
Through deep analysis of NEET and NTA, 176 of the 180 ReNEET 2026 (June 21) questions were already in the MedicNEET question bank before the exam.
176/180MedicNEET's Biology question bank is built from the same NCERT lines NTA picks repeatedly. Not random MCQs — questions crafted exactly like NTA crafts them.