Assertion (A): The movement of tendrils around objects is due to diffe...
b) If Assertion is true but Reason is false
Explanation:
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Assertion (A):
- Statement: "The movement of tendrils around objects is due to differential growth rates in the part of the tendril that is away from the object."
- Explanation: When a tendril comes in contact with an object, it triggers a response known as thigmotropism (growth in response to touch). The cells on the side of the tendril away from the object elongate faster than those in contact, causing the tendril to bend and eventually coil around the support.
- Conclusion: True.
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Reason (R):
- Statement: "Tendrils exhibit positive geotropism as they grow towards the ground."
- Explanation: Geotropism is the directional growth of plants in response to gravity. Positive geotropism means growing towards the gravitational pull (downward), while negative geotropism means growing away from it (upward). Tendrils, in their climbing behavior, exhibit negative geotropism (they grow upward) to reach supports and optimize light exposure. Their coiling is triggered by touch (thigmotropism), not by gravity.
- Conclusion: False.
Since the Assertion is true and the Reason is false, the correct answer is:
b) If Assertion is true but Reason is false.
Assertion (A): The movement of tendrils around objects is due to diffe...
Understanding the Assertion and Reason
The question presents two statements: the Assertion (A) about the movement of tendrils and the Reason (R) regarding their growth direction.
Assertion (A):
- The movement of tendrils around objects is due to differential growth rates in the part of the tendril that is away from the object.
- This is true because tendrils exhibit a phenomenon called thigmotropism, where they respond to touch. When a tendril touches an object, the side touching the object grows more slowly than the opposite side, causing the tendril to coil around the object.
Reason (R):
- Tendrils exhibit positive geotropism as they grow towards the ground.
- This statement is false. Tendrils do not typically exhibit positive geotropism; rather, they often grow upwards or around structures to support the plant, which indicates a negative geotropic response.
Conclusion
- Since the Assertion (A) is true and the Reason (R) is false, the correct answer is option 'B': "If Assertion is true but Reason is false."
- The key point is that while tendrils do move due to differential growth, they do not grow towards the ground, contradicting the Reason.
In summary, the distinction between the truth of the assertion and the falsehood of the reason clarifies why the correct option is 'B'.