Question:
The peg formation in groundnut are positively
The peg formation in groundnut are positively
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The groundnut peg is the structure that carries the fertilized ovary downwards to bury itself in the soil where the pod develops. This downward growth is a response to gravity, known as positive geotropism (or gravitropism).
Updated On: Jul 2, 2026
- Chemotropic
- Thigmotropic
- Geotropic
- Hydrotropic
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The Correct Option is C
Approach Solution - 1
In groundnut (Arachis hypogaea), after fertilization of the flower, a specialized stalk-like structure called a "peg" (or gynophore) develops from the base of the ovary. This peg, carrying the fertilized ovules at its tip, elongates and grows downwards into the soil. The fruit (pod) then develops underground.
This downward growth of the peg into the soil is a classic example of positive geotropism.
Let's define the terms:
Chemotropic: Growth or movement in response to a chemical stimulus.
Thigmotropic: Growth or movement in response to touch or contact.
Geotropic (or Gravitropic): Growth or movement in response to gravity. Positive geotropism is growth towards the direction of gravity (downwards), like roots and the groundnut peg. Negative geotropism is growth away from gravity (upwards), like shoots.
Hydrotropic: Growth or movement in response to water or moisture. The primary directional cue for the groundnut peg's downward growth is gravity. Geotropic
Chemotropic: Growth or movement in response to a chemical stimulus.
Thigmotropic: Growth or movement in response to touch or contact.
Geotropic (or Gravitropic): Growth or movement in response to gravity. Positive geotropism is growth towards the direction of gravity (downwards), like roots and the groundnut peg. Negative geotropism is growth away from gravity (upwards), like shoots.
Hydrotropic: Growth or movement in response to water or moisture. The primary directional cue for the groundnut peg's downward growth is gravity. Geotropic
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Approach Solution -2
Mechanism-based reasoning:
After fertilisation, the groundnut peg (gynophore) shows a strong response to gravity - it bends and grows straight down regardless of the plant's orientation, burying the ovary tip in the soil where the pod then develops.
This directional growth is driven by auxin redistribution under gravity, the same statolith-mediated mechanism that guides root growth, not by touch, chemicals or moisture gradients, which rules out the thigmotropic, chemotropic and hydrotropic options.
Hence the peg's downward growth is correctly classified as positively geotropic.
After fertilisation, the groundnut peg (gynophore) shows a strong response to gravity - it bends and grows straight down regardless of the plant's orientation, burying the ovary tip in the soil where the pod then develops.
This directional growth is driven by auxin redistribution under gravity, the same statolith-mediated mechanism that guides root growth, not by touch, chemicals or moisture gradients, which rules out the thigmotropic, chemotropic and hydrotropic options.
Hence the peg's downward growth is correctly classified as positively geotropic.
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