Darwin's Phototropism and Auxin Discovery — NEET Biology
✅ Asked in NEET 2023The phenomenon which is influenced by auxin and also played a major role in its discovery is: (NEET 2023)
The phenomenon which is influenced by auxin and also played a major role in its discovery is: (NEET 2023)
The Avena curvature is used for bioassay of (NEET 2016 Phase 1)
Answer & NCERT explanation
Correct answer: A — Phototropism
PHOTOTROPISM was influenced by auxin and played major role in its discovery. According to NCERT, Darwin's experiments on phototropism led to auxin discovery. Charles and Francis Darwin observed coleoptile tips bending toward light, which later led to auxin identification. Root initiation, gravitropism, and apical dominance are auxin functions but didn't lead to its discovery.
Read more NCERT concept on the PYQ
Interestingly, the discovery of each of the five major groups of PGRs have been accidental. All this started with the observation of Charles Darwin and his son Francis Darwin when they observed that the coleoptiles of canary grass responded to unilateral illumination by growing towards the light source (phototropism). After a series of experiments, it was concluded that the tip of coleoptile was the site of transmittable influence that caused the bending of the entire coleoptile. Auxin was isolated by F.W. Went from tips of coleoptiles of oat seedlings.
NTA tests students on the historical discovery of auxins through Darwin's phototropism experiments, specifically that the coleoptile tip is the site of a transmittable influence causing bending. A common mistake is confusing the location of perception (tip) with the location of response (lower cells that actually bend), or thinking the entire coleoptile perceived light equally. Remember: the tip detects light and produces a transmittable substance (auxin), which then moves to lower cells causing differential growth and bending toward light. Went isolated this hormone from oat coleoptiles. This concept appears in NEET because it combines historical understanding with hormone physiology and explains how plants sense and respond to environmental stimuli.
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