Discovery of Plant Hormones: Scientists and Experiments
Biology · Plant Growth and Development · NEET
The discovery of plant hormones started by accident. Charles Darwin and his son Francis Darwin saw that canary grass coleoptiles bend towards light (phototropism), and concluded the tip of the coleoptile senses light. Later, F.W. Went isolated auxin from the tips of oat (Avena) coleoptiles. Memory hook: "Darwin Saw, Went Got" — Darwin saw the bending, Went got (isolated) the auxin.
The Darwins observed canary grass coleoptiles bending towards light and found the tip senses it (phototropism). Later, F.W. Went isolated auxin from oat (Avena) coleoptile tips using agar blocks.
Your doubts, answered
Who actually discovered auxin — Darwin or Went?
Neither Darwin isolated it. Charles Darwin and Francis Darwin only observed the bending of canary grass coleoptiles towards light and found the tip is the sensing region. F.W. Went was the one who isolated auxin, from the tips of oat (Avena) coleoptiles. So Darwin observed, Went isolated.
Which plant did the Darwins use, and which plant did Went use?
The Darwins used canary grass coleoptiles for the phototropism observation. Went used oat (Avena) seedling coleoptile tips to isolate auxin. NEET often tries to swap these two plants, so keep them separate: Darwin = canary grass, Went = oat (Avena).
What is a coleoptile and why does it matter here?
A coleoptile is the protective sheath that covers the shoot (plumule) as a grass seedling comes out of the soil. In these experiments the coleoptile bends towards light. The key finding was that the TIP of the coleoptile is the site that senses light and passes a transmittable influence downward, causing the whole coleoptile to bend.
What phenomenon led to the discovery of auxin?
Phototropism — the growth of the coleoptile towards a light source coming from one side (unilateral illumination). This bending towards light was the starting observation that eventually led to auxin's discovery. Gravitropism, apical dominance and root initiation are auxin effects, but they were NOT the phenomenon behind its discovery.
Is the discovery of plant hormones planned or accidental?
NCERT clearly states the discovery of each of the five major groups of PGRs was accidental. The Darwins were studying how plants respond to light, not looking for a hormone. This 'accidental' word is a favourite NCERT one-liner for NEET.
⚠️ The NEET trap ✗ Charles Darwin discovered and isolated auxin from oat coleoptiles. ✓ The Darwins only observed phototropism in canary grass and found the tip senses light. F.W. Went isolated auxin, from oat (Avena) coleoptile tips. 🧠 Darwin = observation (canary grass); Went = isolation (oat). Do not merge them into one person.
Real NEET questions
NEET 2016
The avena curvature is used for bioassay of:
A · ABA
B · GA3
C · IAA ✓
D · Ethylene
Solution: The Avena (oat) coleoptile curvature test is the classic bioassay for auxin (IAA). Auxin applied off-centre on a decapitated coleoptile diffuses down one side and causes measurable curvature. Since auxin was isolated by Went from oat coleoptile tips, the assay is tied to auxin/IAA — not ABA, GA3 or ethylene.
NEET 2023
The phenomenon which is influenced by auxin and also played a major role in its discovery:
A · Gravitropism
B · Apical Dominance
C · Phototropism ✓
D · Root initiation
Solution: The discovery of auxin began with the Darwins observing that canary grass coleoptiles bend towards unilateral light — phototropism. This led to the conclusion that the coleoptile tip transmits the influence causing bending. Gravitropism, apical dominance and root initiation are auxin effects but were not central to its discovery.
Solved Plant Growth and Development NEET PYQs
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Who is called the father of the discovery of plant hormones?
The work of Charles Darwin and Francis Darwin on phototropism in canary grass coleoptiles began the discovery, but auxin itself was isolated by F.W. Went. For NEET, remember Darwin for the observation and Went for the isolation.
From which plant was auxin isolated?
Auxin was isolated by F.W. Went from the tips of coleoptiles of oat (Avena) seedlings. This is a direct NCERT line and a common NEET fact.
Is the discovery of PGRs accidental according to NCERT?
Yes. NCERT states that the discovery of each of the five major groups of plant growth regulators was accidental, starting from the Darwins' phototropism observation.
What did the Darwins conclude from their experiment?
They concluded that the tip of the coleoptile is the site of a transmittable influence that causes the bending of the entire coleoptile towards light.
